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Birch-Type Reduction of Arenes in 2-Propanol Catalyzed by Zero-Valent Iron and Platinum on Carbon

  • Yoshinari Sawama*
    Yoshinari Sawama
    Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
    *E-mail: [email protected] (Y.S.).
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    Orcidhttp://orcid.org/0000-0002-9923-2412
  • , 
  • Kazuho Ban
    Kazuho Ban
    Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
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  • , 
  • Kazuhiro Akutsu-Suyama
    Kazuhiro Akutsu-Suyama
    Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), 162-1 Shirakata, Tokai-Mura, Naka-gun, Ibaraki 319-1106, Japan
    More by Kazuhiro Akutsu-Suyama
    Orcidhttp://orcid.org/0000-0002-4797-6604
  • , 
  • Hiroki Nakata
    Hiroki Nakata
    Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
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  • , 
  • Misato Mori
    Misato Mori
    Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
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  • , 
  • Tsuyoshi Yamada
    Tsuyoshi Yamada
    Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
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    Orcidhttp://orcid.org/0000-0002-6048-5578
  • , 
  • Takahiro Kawajiri
    Takahiro Kawajiri
    Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
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  • , 
  • Naoki Yasukawa
    Naoki Yasukawa
    Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
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  • , 
  • Kwihwan Park
    Kwihwan Park
    Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
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  • , 
  • Yasunari Monguchi
    Yasunari Monguchi
    Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
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    Orcidhttp://orcid.org/0000-0002-2141-3192
  • , 
  • Yukio Takagi
    Yukio Takagi
    Catalyst Development Center, N. E. Chemcat Corporation, 678 Ipponmatsu, Numazu, Shizuoka 410-0314, Japan
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  • , 
  • Masatoshi Yoshimura
    Masatoshi Yoshimura
    Catalyst Development Center, N. E. Chemcat Corporation, 678 Ipponmatsu, Numazu, Shizuoka 410-0314, Japan
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  • , and 
  • Hironao Sajiki*
    Hironao Sajiki
    Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
    *E-mail: [email protected]. Phone/Fax: (+81)-58-230- 8109 (H.S.).
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    Orcidhttp://orcid.org/0000-0003-2792-6826
Cite this: ACS Omega 2019, 4, 7, 11522–11531
Publication Date (Web):July 2, 2019
https://doi.org/10.1021/acsomega.9b01130

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Abstract

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Catalytic arene reduction was effectively realized by heating in 2-propanol/water in the presence of Pt on carbon (Pt/C) and metallic Fe. 2-Propanol acted as a hydrogen source, obviating the need for flammable (and hence, dangerous and hard-to-handle) hydrogen gas, while metallic Fe acted as an essential co-catalyst to promote reduction. The chemical states of Pt and Fe in the reaction mixture were determined by X-ray absorption near-edge structure analysis, and the obtained results were used to suggest a plausible reaction mechanism, implying that catalytic reduction involved Pt- and Fe-mediated single-electron transfer and the dehydrogenation of 2-propanol.

1. Introduction

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Arene reduction is a useful method of preparing cyclohexane derivatives, which are utilized as functional materials, (1) liquid organic hydrogen carriers in the energy field, (2) etc. However, the reduction (hydrogenation) of resonance-stabilized arenes generally requires the use of excess H2 gas, (3) the industrial production of which from fossil fuels such as CH4 is accompanied by CO2 emission. Moreover, the transportation, storage, and usage of H2 gas are strictly regulated by law. (4) Therefore, reduction not involving the utilization of H2 is obviously advantageous from the viewpoint of safety, ease of handling, and avoidance of special equipment usage. Therefore, catalytic transfer hydrogenation using biomass bearing a large amount of alcohol moiety and its analogue-like partial structure within the molecule has been eagerly investigated, (5) and bimetallic Fe- and Pd-catalyzed reductions have also been reported. (6) We have continuously developed methods of heterogeneously catalyzed dehydrogenation of organic substrates (e.g., alcohols (7) and cyclohexane derivatives (8)) and investigated ways of mechanochemical H2 generation from water, (9a,b) alkanes, (9c) and ether (9c) to avoid CO2 emission. Furthermore, we demonstrated that in situ generated H2 can be directly utilized for reduction, (9,10) as exemplified by Pt on carbon (Pt/C)-catalyzed arene reduction in 2-propanol (2-PrOH) as a solvent and hydrogen source (Scheme 1, A). (10b) Unexpectedly, although this reduction proceeded smoothly in a sealed stainless steel tube, it could not be realized in a sealed glass tube. Our recent screening of metallic additives revealed that zero-valent Fe is an essential co-catalyst for arene reduction (Scheme 1, B). Although a bimetallic system containing Pt and Fe was previously utilized to control the catalyst activity in the hydrogenation of ethylene, (11a) cinnamaldehyde, (11b) and other aldehydes, (11c,d) all of these reductions could be realized in the presence of Pt alone. Hydrogenations promoted by bimetallic catalysts comprising Fe and Pt group metals other than Pt (Rh, (12a) Pd, (11c,12b,c) and Ru (11c)) were also reported, and the performances of these catalysts were heavily reliant on the reaction conditions. For example, Pt–Fe (11d) and Pd–Fe (12b) catalysts inhibited the hydrogenation of furan and benzene rings. Herein, we demonstrate that Pt/C-catalyzed arene reduction can be switched on/off by the presence/absence of Fe and perform X-ray absorption near edge spectroscopy (XANES) analysis to suggest a mechanistic explanation. The metal-containing reaction apparatus, such as a sealed stainless steel tube, etc., is generally utilized in the reactions under high-pressure and high-temperature conditions. In contrast with the Pt/C- and Fe-catalyzed arene reduction, H–D exchange reaction of arenes could proceed without the reduction of arene moiety in the glass flask under the similar reaction conditions using Pt/C in 2-PrOH and D2O instead of H2O. (13) Therefore, the present phenomenon is valuable to alert the chemists about the effect of reaction apparatus.

Scheme 1

Scheme 1. Pt/C–Fe-Catalyzed Arene Reduction in 2-Propanol as a Solvent and Hydrogen Source
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2. Results and Discussion

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n-Heptylbenzene (1a, 0.5 mmol) could not be catalytically reduced by 3 h of heating at 100 °C in a sealed glass tube containing Pt/C, 2-PrOH (4 mL), and H2O (2 mL) (Table 1, entry 1). On the other hand, this reduction proceeded in the presence of the zero-valent Fe (5 mol %) as a main component of stainless steel to produce the corresponding cyclohexane derivative (2a) in excellent isolated yield (98%). The above reduction also proceeded in the presence of Zn and Co as co-catalysts, although lower conversions were obtained (entries 3 and 4). The use of Ni and Cr as other major stainless steel components was ineffective, as was the case for Cu, Al, and Mg (entry 5). Although 2a could be obtained in the presence of iron oxides (FeO and Fe2O3) in moderate yields (entries 6 and 7, respectively), these reductions were incomplete within 3 h. Heterogeneous platinum-group metal catalysts other than Pt/C (e.g., Pd/C and Rh/C) were ineffective for the above reduction even in the presence of Fe (entries 8 and 9), and no conversion was observed when Fe was used as the only catalyst (entry 10). The deference of reactivity of Pt/C, Pd/C, or Rh/C cannot be explained. Furthermore, the reduction efficiency decreased with decreasing reaction temperature (entry 11, 80 °C), and no reduction was observed at 50 °C (entry 12). Notably, gram-scale reduction of 1a (1.3 g, 7.4 mmol) afforded 2a in 97% isolated yield (entry 13).
Table 1. Effect of Metal Co-catalyst on the Reduction of n-Heptylbenzene
entrycatalystadditive1a/2aa (mol/mol)
110% Pt/C no reaction
210% Pt/CFe0/100 (98)b
310% Pt/CZn76/24
410% Pt/CCo89/11
510% Pt/CNi, Cr, Cu, Al, or Mgno reaction
610% Pt/CFeO33/67
710% Pt/CFe2O325/75
810% Pd/CFeno reaction
910% Rh/CFeno reaction
10 Feno reaction
11c10% Pt/CFe47/53
12d10% Pt/CFeno reaction
13e10% Pt/CFe0/100 (97)b
a

Ratio was determined by 1H NMR.

b

Isolated yield.

c

At 80 °C.

d

At 50 °C.

e

7.4 mmol of 1a (1.3 g) was used as a substrate.

The above reduction could be carried out in a 2-PrOH (4 mL)–H2O mixture (7a) (Table 1, entry 2; Table 2, entry 1), which allowed one to decrease the risk posed by the pyrophoric nature of Pt/C. While the arene reduction was also completely performed using 3 mL of 2-PrOH, further decrease of 2-PrOH usage to 2 mL caused the incomplete reduction within 3 h (see the Supporting Information). On the other hand, the reduction was completely inhibited by the use of 1-PrOH or t-BuOH as co-solvents (Table 2, entries 2 and 3). Furthermore, pure H2O could not be employed as a hydrogen source (entry 4). Importantly, reduction in the 2-PrOH–H2O mixture was more effective than reduction in pure H2O under H2 atmosphere (entry 5).
Table 2. Effect of Solvent on Arene Reduction Efficiency
entrysolvent1a/2aa (mol/mol)
12-PrOH (4 mL)/H2O (2 mL)0/100 (98)b
21-PrOH (4 mL)/H2O (2 mL)no reaction
3t-BuOH (4 mL)/H2O (2 mL)no reaction
4H2O (6 mL)no reaction
5cH2O (6 mL)11/89
a

Ratio was determined by 1H NMR.

b

Isolated yield.

c

Under H2 atmosphere.

The arene nuclei of cyclohexylbenzene (1b), t-butylbenzene (1c), and acetanilide (1d) effectively underwent Pt/C–Fe-catalyzed reduction in 2-PrOH/H2O to produce the corresponding cyclohexane derivatives (2b–2d, Scheme 2). Anthracene (1e) was partially reduced to 1,2,3,4,5,6,7,8-octahydroanthracene (2e) in good yield. Toluene (1f) could be smoothly transformed to methylcyclohexane (2f), which is viewed as a promising hydrogen storage material for creating a hydrogen society, (2) without the external addition of hydrogen. In all cases, substrates (1b–1f) were completely reduced without any byproduct formation.

Scheme 2

Scheme 2. Substrate Scope of the Reduction Reaction
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a10% Pt/C (10 mol %) and Fe0 (10 mol %) were used.

Although the Pt/C–Fe-catalyzed reduction of stilbene (3) hardly proceeded in 2-PrOH/H2O at 25 or 40 °C (Table 3, entries 1 and 2, respectively), the olefin functionality of 3 was selectively reduced at 60 °C without the reduction of arene nuclei to produce 1,2-diphenylethane (4) in 98% isolated yield (entry 3). However, olefin reduction was hardly catalyzed at 60 °C by Pt/C in the absence of Fe (entry 4). On the other hand, both olefin and arene functionalities of 3 were reduced in the presence of Pt/C and Fe (5 mol % each) at 100 °C (12 h) to afford 1,2-dicyclohexylethane (5) in quantitative yield (entry 5). 7-Tetradecene (6), bearing no aromatic nucleus within the molecule, also efficiently underwent Pt/C–Fe-catalyzed reduction of the olefin functionality at 60 °C to give tetradecane (7) in 88% yield, while 11% of 6 was recovered (Scheme 3). Complete reduction was observed at 100 °C, furnishing 7 in 97% isolated yield. Meanwhile, in the absence of Fe powder, 6 was completely recovered at 60 and 100 °C.

Scheme 3

Scheme 3. Reduction of 7-Tetradecene under Different Conditions
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Table 3. Reduction of Stilbene under Different Conditions
  yield (%)
entrytemp. (°C)recovered 345
12510000
24075180
3600980
4a609630
51000099
a

Without Fe.

Subsequently, we compared the hydrogenation activities of Pt/C–Fe, Pt/C, and Fe in 1-PrOH (poor hydrogen source; Table 2, entry 2) and H2O at 100 °C under H2 (1 atm, 1 h; Scheme 4). In the case of Pt/C–Fe (5 mol % Pt and Fe each), 11% of 1a was reduced, and 89% of 1a was recovered, whereas 2a was obtained in 17% yield when Pt/C was used on its own, and no hydrogenation was observed when Fe was employed on its own. These results indicated that under the conditions of the Pt/C–Fe-catalyzed reaction, Fe does not facilitate Pt/C-catalyzed hydrogenation, with H2 gas generated in situ by the Pt/C-catalyzed dehydrogenation of 2-PrOH (Table 1, entry 2). Thus, as has previously been reported, (11) the accelerating effect of combining Pt and Fe on hydrogenation was not observed in the present arene reduction.

Scheme 4

Scheme 4. Comparison of Pt/C–Fe, Pt/C, and Fe Hydrogenation Activities
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Figure 1 shows the time profiles of the internal pressure in a 50 mL sealed glass tube containing 2-PrOH/H2O at 100 °C under various conditions, and Table 4 lists the total yields of the in situ generated H2 determined by gas chromatography thermal conductivity detection (GC–TCD). The reduction of 1a (0.5 mmol) in 2-PrOH (4 mL)–H2O (2 mL) in the presence of 10% Pt/C (5 mol %: 0.025 mmol) and Fe (5 mol %: 0.025 mmol) at 100 °C was complete within 3 h (Table 1, entry 2). The internal pressure after 3 h reached ∼2 atm, and no further increase was observed after the completion of arene reduction (Figure 1, conditions A), with the yield of H2 after 6 h equaling only 0.33 mmol (Table 4, entry 1). Heating of the 2-PrOH-H2O mixture only resulted in a slight increase of the internal pressure up to ∼2 atm due to simple vaporization and thermal expansion of the fluid and gas (air) (conditions B). These results indicated that the developed arene reduction could safely proceed without the generation of excessive amounts of high-pressure flammable H2 gas. Since Fe did not catalyze H2 generation in 2-PrOH/H2O (conditions C), H2 generation by corrosion (oxidation) of Fe in the aqueous solution was ruled out. (14) The simple use of Pt/C in 2-PrOH/H2O resulted in the generation of a massive amount of propane (116.2 mmol) by Pt/C-catalyzed hydrodeoxygenation, (15) while only traces of H2 were concomitantly produced (conditions D). On the other hand, the generation of propane could be suppressed by the use of Fe powder along with Pt/C (conditions E). Furthermore, the addition of 1a to the solvent mixture containing Pt/C but no Fe powder suppressed the generation of C3H8 and H2, while no reduction of the aromatic nucleus was observed (conditions F). Probably, Pt metal was strongly coordinated by arene nuclei, which inhibited the Pt/C-catalyzed dehydrogenation and hydrodeoxygenation of 2-PrOH.

Figure 1

Figure 1. Time profile of the internal pressure inside a 50 mL sealed glass tube filled with different reaction mixtures.

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Table 4. Gaseous Products Produced under the Conditions of Figure 1 after 6 h
  internal gas (mmol)
entryconditionsH2C3H8
1A0.330.57
2aBnot detectednot detected
3Cnot detectednot detected
4Dtrace116.2
5E0.292.7
6Fnot detectednot detected
a

For 3 h.

To elucidate the mechanism of arene reduction, the mean valence of Fe in reaction mixtures was analyzed by XANES. As noted in the Introduction section, the Pt/C-catalyzed reduction of 1a proceeded only in a stainless steel vessel, while the addition of Fe (5 mol %) allowed this reduction to be performed in a glass tube. Figure 2 shows the X-ray fluorescence profiles of the reaction mixtures A and B (Scheme 1) after 3 h of heating, revealing that these mixtures contained 4.4 and 5.0 mmol Fe, respectively, as determined from the peak integral values. These findings clearly confirmed the leaching of Fe from stainless steel during the reaction.

Figure 2

Figure 2. X-ray fluorescence profiles of the mixtures A and B (see Scheme 1).

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The valences of Fe and Pt in the mixtures A and B after reduction were determined from Fe K-edge (Figure 3) and Pt LIII-edge (Figure 4) XANES spectra of these mixtures using Fe0 powder, Pt0 foil, FeCl3, and PtCl4 as standards (detailed descriptions are provided in the Supporting Information). Compared with each energy based on the absorption edge energy shift (normalized absorbance = 0.5 in Figure 3a), the Fe K-edge absorptions of the samples A and B were shifted to higher energies than that of the zero-valent Fe, (16) and the mean valence of Fe in these samples was estimated as 1.57 and 1.50, respectively (Figure 3b).

Figure 3

Figure 3. (a) Normalized Fe K-edge XANES profiles. (b) Plot of Fe K-edge absorption edge energy shift vs the valence of Fe. Reaction conditions A and B are described in Scheme 1.

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Figure 4

Figure 4. (a) Normalized Pt LIII-edge XANES profiles. (b) Plot of Pt LIII-edge absorption edge energy shift vs the valence of Pt. Reaction conditions A and B are described in Scheme 1.

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X-ray absorption fine structure (XAFS) and polarized neutron reflectivity (PNR) analyses also strongly supported the generation of oxidized Fe ions during the reduction (see the Supporting Information). Similarly, the analysis of Pt LIII-edge XANES spectra (Figure 4a) in comparison with the absorption peak energy (absorbance = 0.5) (17) revealed that the absorption peaks of the samples A and B shifted to higher energies (i.e., to higher oxidation states) than that of zero-valent Pt metal (Figure 4b). (18) As a result, the valence of Pt in both A and B samples after reduction was determined to be 1.51 and 1.32, respectively, which indicated that both A and B reactions were triggered by electron transfer from Pt and Fe metals to the aromatic ring to form partially oxidized Pt and Fe ions.
Two reaction mechanisms were proposed based on these findings (Scheme 5). First, the Pt/C-catalyzed dehydrogenation of 2-PrOH produces H2, which can be consumed in the traditional Pt/C-catalyzed arene (1) hydrogenation (3) and acetone (route a). In situ generated H2 rapidly reacts with acetone to afford 2-PrOH, which suppresses the accumulation of excess H2 in the vessel. Although the role of Fe is unclear, its addition promotes the dehydrogenation of 2-PrOH (Table 4, conditions A vs F) and suppresses the hydrodeoxygenation of 2-PrOH to propane, precluding the consumption of H2 required for arene hydrogenation (Table 4, conditions D vs E). As shown in Table 2, entries 2 and 3, arene reduction cannot be achieved when 2-PrOH is substituted for 1-PrOH or t-BuOH. This behavior is ascribed to the fact that Pt-group metal/C-catalyzed dehydrogenation of primary alcohols is accompanied by several side reactions such as decarbonylation of intermediate aldehyde derivatives, (7b) which can retard arene reduction, while tertiary alcohols without α-protons cannot act as H2 sources. Therefore, Pt/C–Fe-catalyzed arene reduction effectively proceeds only in 2-PrOH.

Scheme 5

Scheme 5. Proposed Mechanisms or Pt/C–Fe-Catalyzed Arene Reduction
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Alternatively, arene reduction can take place via single electron transfer (SET) analogously to the Birch reduction (route b). SET from zero-valent Pt metal (18) to the arene nucleus of the charge transfer complex (A) formed from 1, and Pt/C gives a radical anion intermediate (B) that is immediately protonated by 2-PrOH or H2O to form C. The subsequent second SET and protonation afford a 1,3-cyclohexadiene intermediate (E) complexed by PtII. PtII smoothly accepts electrons from Fe0 to regenerate Pt0 (F) and produce FeII, which is immediately reduced to Fe0 by H2 generated via Pt/C-catalyzed dehydrogenation of 2-PrOH (route a). Repetition of SET and protonation processes afford cyclohexane product 2 and regenerated Pt0 (catalytic cycle 1). The PtI intermediate C can also be reduced to Pt0 by Fe0 to produce intermediate G and FeI. Subsequent SET within G and the protonation of anion intermediate H furnishes a diene–PtI complex (I). PtI can then be reduced by FeI to generate a diene–Pt0 complex J (catalytic cycle-2), and the resulting FeII species are reduced to Fe0 by H2 derived from 2-PrOH. The mean valence of Pt (1.32 and 1.51) determined by XANES analysis supports the operation of catalytic cycle 1, which involves redox shuttling between Pt0 and PtII. The release of PtII from complex E in the absence of catalytic Fe powder should afford traces of diene intermediate K. Notably, 1a was completely recovered under the conditions of Pt/C catalysis in the absence of Fe (Table 1, entry 1). On the other hand, unsaturated cyclohexane derivatives such as cyclohexadiene and cyclohexene easily undergo Pt-group metal-catalyzed dehydrogenative aromatization in H2O to form the corresponding benzene derivatives. (8a) Therefore, diene intermediate K might be immediately transformed to 1 via Pt-catalyzed dehydrogenation. Indeed, a mixture of toluene (8; 0.95 mmol) and 1-methyl-1,4-cyclohexadiene (9; 0.05 mmol) as a model of the corresponding diene intermediate (K) was smoothly converted to toluene (8; 0.99 mmol) as the sole product via the dehydrogenation of K under conditions of 2-PrOH-free aqueous Pt/C catalysis in both the presence and absence of Fe (Scheme 6). (19) K2PtCl4 and PtO2 also catalyzed the dehydrogenation of 9, which resulted in the formation of 8. Furthermore, the use of 1-PrOH or t-BuOH instead of 2-PrOH should afford diene intermediates equivalent to K, since in these cases, Fe0 cannot be regenerated from FeII because of the poor (or absence of) H2 generation ability of these alcohols. The regeneration of 1 from K also causes the complete recovery of 1 when 1-PrOH and t-BuOH are used as solvents (Table 2, entries 2 and 3). Meanwhile, the (Pt/C (5 mol %) + 2-PrOH)-mediated reduction of the olefin functionality of stilbene (3) in the absence of Fe proceeded to an insignificant extent to produce 1,2-diphenylethane (4, 3% yield) via the SET mechanism not involving redox shuttling between PtI/PtII and Pt0 (Table 3, entry 4). This finding was ascribed to the fact that the dehydrogenation of the saturated ethylene function of 4 to 3 was not catalyzed by Pt/C in H2O (Scheme 7). The consecutive generation of appropriate quantities of H2 via Pt/C–Fe-catalyzed dehydrogenation of 2-PrOH for the regeneration of Fe0 from FeII was required to maintain the catalytic cycle for effective arene reduction, although a FeI, FeII, and FeIII cycle for the repeatable regeneration of Pt0 cannot be ruled out.

Scheme 6

Scheme 6. Pt-Catalyzed Dehydrogenative Regeneration of Toluene (8) from Cyclohexadiene Derivative 9
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Scheme 7

Scheme 7. Results of 1,2-Diphenylethane (4) Reduction under the Conditions of Pt/C Catalysis
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Route b seems to be preferred over route a, since (a) reduction with 2-PrOH as a hydrogen source is faster than that with excess amount of H2 gas (Table 2, entry 1 vs 5) and (b) a small amount of H2 is generated by the use of Pt/C and Fe in 2-PrOH/H2O (Table 4, entry 5). Whereas the traditional Birch reduction of arenes by stoichiometric amounts of Na in liquid NH3 gives 1,4-cyclohexadienes via SET followed by protonation, the present reduction method directly affords cyclohexane derivatives. (20)
The H–D exchange reaction of acetanilide (1d) could proceed in the presence of Pt/C in a 2-PrOH and D2O-mixed solvent without arene reduction to give the deuterated acetanilide (1da-dn) (Scheme 8, top). (13a) Under the present arene reduction conditions using Pt/C and Fe as catalysts in D2O instead of H2O, both H–D exchange reaction and arene reduction were carried out to give the deuterium-labeled cyclohexane derivatives (2db-dn) with moderate D content (middle). Meanwhile, the use of 2-PrOD-d8 instead of 2-PrOH reduced the reaction efficiencies of both arene reduction and H–D exchange reaction (bottom). Probably, the Pt/C-catalyzed dehydrogenation of 2-PrOD-d8 was suppressed due to the isotopic effect causing a stronger C–D bond at the α-position of 2-PrOD-d8, and the enough amount of deuterium, which is essential to regenerate the zero-valent catalyst (Scheme 5), was not produced. The low D contents of 2dc-dn indicated that the protonation (Scheme 5) is mainly derived from water. The similar Pt/C-catalyzed reaction conditions using 2-PrOH and D2O may induce the H–D exchange reaction of hydrocarbon, such as cyclohexane moiety. (13d) Namely, the effect using deuterated solvents cannot be clearly explained, since three reactions (H–D exchange reactions of arene and hydrocarbon and arene reduction) can proceed under Pt/C- and Fe-catalyzed reaction conditions. At least, it is certain that the additional Fe is required to facilitate the desired Pt/C-catalyzed arene reduction using 2-PrOH.

Scheme 8

Scheme 8. Reaction Using Deuterated Solventsa
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aItalic number means the deuterium content

3. Conclusions

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Pt/C–Fe-catalyzed arene reduction with 2-PrOH as a hydrogen source under ambient-pressure conditions was developed. The Pt/C-catalyzed in situ production of H2 via the dehydrogenation of 2-PrOH was shown to play a critical role in the regeneration of the composite catalyst to promote arene reduction. Since only small amounts of H2 accumulated in the reaction vessel after reduction, the present method was concluded to be useful from the viewpoint of safety. The presence of a catalytic amount of Fe was found to be crucial for the external hydrogen-free reduction of aromatic nuclei in aqueous 2-PrOH.

4. Experimental Section

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4.1. General Information

Ten percent Pt/C, Pd/C, Rh/C, and Ru/C were supplied by the N. E. Chemcat Corporation (Tokyo, Japan). 1-PrOH, 2-PrOH, t-BuOH, and water were purchased from commercial sources and used without further purification. All of the commercially available reagents were used without further purification. Reactions were carried out in 50 mL glass sealed tube [tinyclave steel (Büchiglasuster, Switzerland)] or 15 × 150 m/m test tube. 1H NMR spectra were recorded on a JEOL ECZ 400 or ECA 500 spectrometer at room temperature in CDCl3 as a solvent and internal standard (1H NMR: δ = 7.26 for CDCl3) with tetramethylsilane as a further internal standard. A JMS Q1000 GC [7890A gas chromatography (Agilent Technologies, USA) equipped with a JEOL MK II mass spectrometer (JEOL Co., Ltd., Japan)] and an Inert Cap5MS/sil capillary column (30 × 0.25 mm i.d., 0.25 μm film thickness; GL Science, Japan) were used for toluene and methylcyclohexane analyses. GC-3200 [gas chromatography equipped with thermal conductivity detector (GC/TCD; GL Science, Japan)] was used for gas analysis with Molecular Sieve 5 Å (60/80 mesh) packed column (3 × 2.2 mm i.d., 1/8 inch: GL Science, Japan) for H2 analysis, Porapak Q (80/100 mesh) packed column (2 × 2.2 mm i.d., 1/8 inch: GL Science, Japan) for C3H8 analysis. EXAFS measurements of solutions were performed using the fluorescence mode at the BL11S2 Hard X-ray EXAFS beamline station in the Aichi SR. The incident X-rays were monitored by an ionization chamber (14 cm in length) filled with N2 gas.

4.2. General Procedure for Arene Reduction (Tables 1–3; Schemes 2 and 3)

4.2.1. Reduction of n-Heptylbenzene, Cyclohexylbenzene, tert-Butylbenzene, or Anthracene

A 50 mL sealed glass tube was sequentially charged with arene (0.50 mmol), Fe0 (1.4 mg, 0.025 mmol, 5 mol %), 10% Pt/C (48.8 mg, 0.025 mmol, 5 mol %), H2O (2 mL), and 2-PrOH (4 mL), and the suspension was stirred at 100 °C (Caution: the addition of 2-PrOH in the absence of H2O causes the ignition of Pt/C). After stirring for a specific reaction time, the mixture was cooled to room temperature and filtered through a membrane filter (Millipore, Millex-LH, 0.2 μm) to remove catalysts. The filtrate was extracted with Et2O (20 mL) diluted with H2O (20 mL), and the aqueous layer was further extracted with Et2O (3 × 10 mL). The organic layer was dried over anhydrous MgSO4, filtered, and concentrated in vacuo to give the cyclohexane product.

4.2.2. Reduction of Toluene

A 50 mL sealed glass tube was sequentially charged with toluene (1f; 46.1 mg, 0.50 mmol), Fe0 (2.8 g, 0.050 mmol, 10 mol %), 10% Pt/C (97.6 g, 0.050 mmol, 10 mol %), H2O (2 mL), and 2-PrOH (4 mL), and the suspension was stirred at 100 °C (Caution: the addition of 2-PrOH in the absence of H2O causes the ignition of Pt/C). After stirring for 3 h, the mixture was cooled to room temperature and anisole added (50 μL) as an internal standard. The mixture was filtered through a membrane filter (Millipore, Millex-LH, 0.2 μm) to remove catalysts. The filtrate was transferred to a 50 mL volumetric flask with Et2O. Twenty microliters of the sample was dissolve in 1.5 mL of Et2O. 2f was determined by GC-MS and yield was 82%. Helium was employed as a carrier gas at the flow rate of 1.3 mL/min. The injector and detector temperatures were 280 °C. The column temperature was programmed to ramp from 35 °C (1 min hold) to 110 °C (3 min hold) at the rate of 5 °C/min and then to 280 °C (1.5 min hold) at the rate of 30 °C/min. One microliter of the sample solution was injected (split; 1:10). The products were identified by their GC/MS retention times in comparison to those of authentic commercial samples. Retention times (min) were 3.53 (methylcyclohexane), 4.14 (toluene), and 8.40 (internal standard) (Anisole).

4.2.3. Reduction of Stilbene and 7-Tetradecene

A test tube was sequentially charged with alkene (0.25 mmol), Fe0 (0.7 mg, 0.013 mmol, 5 mol %), 10% Pt/C (24.4 mg, 0.013 mmol, 5 mol %), H2O (1 mL), and 2-PrOH (2 mL), and the suspension was stirred at 100 °C (Caution: the addition of 2-PrOH in the absence of H2O causes the ignition of Pt/C). After stirring for a specific reaction time, the mixture was cooled to room temperature and filtered through a membrane filter (Millipore, Millex-LH, 0.2 μm) to remove the catalysts. The filtrate was extracted with Et2O (20 mL), diluted with H2O (20 mL), and the aqueous layer was further extracted with Et2O (3 × 10 mL). The organic layer was dried over anhydrous MgSO4, filtered, and concentrated in vacuo to give the alkane product.

4.3. Analysis of the Internal Gas Components (Figure 1 and Table 4)

A 50 mL sealed glass tube was sequentially charged with n-heptylbenzene (1a; 88.3 mg, 0.50 mmol), Fe0 (1.4 mg, 0.025 mmol, 5 mol %), 10% Pt/C (48.8 mg, 0.025 mmol, 5 mol %), H2O (2 mL), and 2-PrOH (4 mL), and the suspension was stirred at 100 °C. Pressure gauge on the glass sealed tube was checked at 5, 10, 30 min, 1, 2, 3, 4, 5, and 6 h. After 6 h, the mixture was cooled to room temperature and the amounts of H2 and C3H8 were detected from the analysis of the headspace gas by GC/TCD. Helium was employed as a carrier gas at 220 kPa (molecular sieve 5 Å) and 140 kPa (Porapak Q). The injector and detector temperatures were 100 °C. The column temperature was programmed to 70 °C. One milliliter of sample gas was injected. The products were identified by their GC/TCD retention times in comparison to those of authentic commercial samples. Retention times (min) were 1.3 (H2, Molecular Sieve 5 Å) and 13.7 (C3H8, Porapack Q).

4.4. General Procedure for Arene Reduction under Hydrogen Condition (Scheme 4)

A 50 mL sealed glass tube was sequentially charged with n-heptylbenzene (1a; 88.3 mg, 0.50 mmol), Fe0 (1.4 mg, 0.025 mmol, 5 mol %), 10% Pt/C (48.8 mg, 0.025 mmol, 5 mol %), H2O (2 mL), and 1-PrOH (4 mL). The inside air was replaced with H2 (balloon) in five vacuum/argon cycles, and the suspension was stirred at 100 °C. After stirring for 1 h, the mixture was cooled to room temperature and filtered through a membrane filter (Millipore, Millex-LH, 0.2 μm) to remove the catalysts. The filtrate was extracted with Et2O (20 mL), diluted with H2O (20 mL), and then the aqueous layer was further extracted with Et2O (3 × 10 mL). The organic layer was dried over anhydrous MgSO4, filtered, and concentrated in vacuo to give the cyclohexane product.

4.5. General Procedure for the Dehydrogenation of Cyclohexadiene Derivative (9) Mixed with Small Amount of Arene (8) (Scheme 6, Equation 1)

A 30 mL co-plug test tube was sequentially charged with toluene (8; 100 μL, 0.95 mmol), 1-methyl-1,4-cyclohexadiene (9; 5.6 μL, 0.05 mmol), Fe0 (2.8 mg, 0.050 mmol), 10% Pt/C (97.6 mg, 0.050 mmol) and H2O (6 mL), and the suspension was stirred at 100 °C. After stirring for 1 h, the mixture was cooled to room temperature and anisole (100 μL) added as an internal standard. The mixture was filtered through a membrane filter (Millipore, Millex-LH, 0.2 μm) to remove the catalysts. The filtrate was transferred to a 100 mL volumetric flask with Et2O. Twenty microliters of the sample was dissolve in 1.5 mL of Et2O. Compound 9 was detected by GC/MS.

4.6. General Procedure for Dehydrogenation of 1,2-Diphenylethane (4) Mixed with Small Amount of Stilbene (3) (Scheme 6, Equation 2)

A 50 mL sealed glass tube was sequentially charged with stilbene (3; 171.2 mg, 0.95 mmol), 1,2-diphenylethane (4; 9.1 mg, 0.05 mmol), Fe powder (2.8 mg, 0.050 mmol), 10% Pt/C (97.6 mg, 0.050 mmol), and H2O (6 mL), and the suspension was stirred at 100 °C. After stirring for 1 h, the mixture was cooled to room temperature and filtered through a membrane filter (Millipore, Millex-LH, 0.2 μm) to remove the catalysts. The filtrate was extracted with Et2O (20 mL), diluted with H2O (20 mL), and the aqueous layer was further extracted with Et2O (3 × 10 mL). The organic layer was dried over anhydrous MgSO4, filtered, and concentrated in vacuo to give the products.

4.7. Spectroscopic Data of the Products

4.7.1. n-Heptylcyclohexane (2a) in Tables 1 and 2

n-Heptylbenzene (1a; 88.3 mg, 0.50 mmol), Fe0 (5 mol %), 10% Pt/C (5 mol %), H2O (2 mL), and 2-PrOH (4 mL) were used, and the reaction was carried out according to the general procedure shown in Section 4.2.1 to give 2a (92.2 mg, 0.49 mmol) in 98% yield. Scale-up study (Table 1, entry 13): A 200 mL two-neck round-bottom flask was sequentially charged with n-heptylbenzene (1a; 1.30 g, 7.40 mmol), Fe powder (21.3 mg, 0.38 mmol, 5 mol %), 10% Pt/C (731.4 mg, 0.37 mmol, 5 mol %), H2O (15 mL), and 2-PrOH (30 mL). The air inside was replaced with argon (balloon) by five vacuum/argon cycles, and the suspension was stirred at 100 °C. After stirring for 4 h, the mixture was cooled to room temperature and filtered through celite pad to remove catalysts. The filtrate was extracted with Et2O (40 mL) and H2O (40 mL), and then the aqueous layer was further extracted with Et2O (3 × 20 mL). The organic layer was dried over anhydrous MgSO4, filtered, and concentrated in vacuo to give 2a (1.32 mg, 7.21 mmol) in 97% yield. Colorless oil; 1H NMR (400 MHz, CDCl3): δ 1.75–1.67 (m, 5H), 1.31–1.12 (m, 16H), 0.94–0.85 (m, 5H). 1H NMR spectrum of the product was identical to that of the ref (10b).

4.7.2. Bicyclohexyl (2b) in Scheme 2

Cyclohexylbenzene (1b; 80.1 mg, 0.50 mmol), Fe0 (1.4 mg), 10% Pt/C (5 mol %), H2O (2 mL), and 2-PrOH (4 mL) were used, and the reaction was carried out according to the general procedure shown in Section 4.2.1 to give 2b (75.1 mg, 0.45 mmol) in 90% yield. Colorless oil; 1H NMR (500 MHz, CDCl3): δ 1.74–1.62 (m, 10H), 1.24–0.89 (m, 12H). 1H NMR spectrum of the product was identical to that of the ref (10b).

4.7.3. tert-Butylcyclohexane (2c) in Scheme 2

tert-Butylbenzene (1c; 67.1 mg, 0.50 mmol), Fe0 (5 mol %), 10% Pt/C (5 mol %), H2O (2 mL), and 2-PrOH (4 mL) were used, and the reaction was carried out according to the general procedure shown in Section 4.2.1 to give 2c (53.5 mg, 0.382mmol) in 78% yield. Colorless oil; 1H NMR (500 MHz, CDCl3): δ 1.76–1.63 (m, 5H), 1.26–0.84 (m, 15H). 1H NMR spectrum of the product was identical to that of the ref (3s).

4.7.4. N-Cyclohexylacetamide (2d) in Scheme 2

Acetanilide (1d; 67.6 mg, 0.50 mmol), Fe0 (5 mol %), 10% Pt/C (5 mol %), H2O (2 mL), and 2-PrOH (4 mL) were used, and the reaction was carried out according to the general procedure shown in Section 4.2.1 to give 2d (66.1 mg, 0.47 mmol) in 94% yield. Colorless solid; 1H NMR (500 MHz, CDCl3): δ 6.09 (brs, 1H), 3.68–3.63 (m, 1H), 1.88–1.81 (m, 5H), 1.64–1.52 (m, 3H), 1.29–1.02 (m, 5H). 1H NMR spectrum of the product was identical to that of the ref (10b).

4.7.5. 1,2,3,4,5,6,7,8-Octahydroanthracene (2e) in Scheme 2

Anthracene (1e; 89.1 mg, 0.50 mmol), Fe0 (5 mol %), 10% Pt/C (5 mol %), H2O (2 mL), and 2-PrOH (4 mL) were used, and the reaction was carried out according to the general procedure shown in Section 4.2.1 to give 2e (85.6 mg, 0.46 mmol) in 92% yield. Colorless solid; 1H NMR (500 MHz, CDCl3): δ 6.82 (s, 2H), 2.73 (m, 8H), 1.80 (m, 8H). 1H NMR spectrum of the product was identical to that of the ref (10b).

4.7.6. 1,2-Diphenylethane (4) in Table 3, Entry 3

Stilbene (3; 45.1 mg, 0.25 mmol), Fe powder (5 mol %), 10% Pt/C (5 mol %), H2O (1 mL), and 2-PrOH (2 mL) were used, and the reaction was carried out according to the general procedure shown in Section 4.2.3 to give 4 (44.7 mg, 0.25 mmol) in 98% yield. Colorless solid; 1H NMR (400 MHz, CDCl3): δ 7.33–7.20 (m, 10H), 2.95 (s, 4H). 1H NMR spectrum of the product was identical to that of the ref (21).

4.7.7. 1,2-Dicyclohexylethane (5) in Table 3, Entry 4

Stilbene (3; 45.1 mg, 0.25 mmol), Fe powder (5 mol %), 10% Pt/C (5 mol %), H2O (1 mL), and 2-PrOH (2 mL) were used, and the reaction was carried out according to the general procedure shown in Section 4.2.3 to give 5 (48.1 mg, 0.25 mmol) in 99% yield. Colorless oil; 1H NMR (400 MHz, CDCl3): δ 1.70–1.62 (m, 10H), 1.26–1.12 (m, 12H), 0.89–0.84 (m, 4H). 1H NMR spectrum of the product was identical to that of the ref (10b).

4.7.8. Tetradecane (7) in Scheme 3

7-Tetradecene (6; 49.1 mg, 0.25 mmol), Fe powder (5 mol %), 10% Pt/C (5 mol %), H2O (1 mL), and 2-PrOH (2 mL) were used, and the reaction was carried out according to the general procedure shown in Section 4.2.3 to give 7 (47.1 mg, 0.24 mmol) in 97% yield. Colorless oil; 1H NMR (400 MHz, CDCl3): δ 1.32–1.26 (m, 24H), 0.90–0.86 (m, 6H). 1H NMR spectrum of the product was identical to that of the ref (22).

Supporting Information

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The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.9b01130.

  • XANES, EXAFS, and PNR analysis, XPS of fresh 10% Pd/C, mechanism study, and spectroscopic data of the products (PDF)

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Author Information

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  • Corresponding Authors
  • Authors
    • Kazuho Ban - Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
    • Kazuhiro Akutsu-Suyama - Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), 162-1 Shirakata, Tokai-Mura, Naka-gun, Ibaraki 319-1106, Japan;  Orcidhttp://orcid.org/0000-0002-4797-6604
    • Hiroki Nakata - Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
    • Misato Mori - Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
    • Tsuyoshi Yamada - Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan;  Orcidhttp://orcid.org/0000-0002-6048-5578
    • Takahiro Kawajiri - Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
    • Naoki Yasukawa - Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
    • Kwihwan Park - Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
    • Yasunari Monguchi - Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan;  Present Address: Laboratory of Organic Chemistry, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan (Y.M.);  Orcidhttp://orcid.org/0000-0002-2141-3192
    • Yukio Takagi - Catalyst Development Center, N. E. Chemcat Corporation, 678 Ipponmatsu, Numazu, Shizuoka 410-0314, Japan
    • Masatoshi Yoshimura - Catalyst Development Center, N. E. Chemcat Corporation, 678 Ipponmatsu, Numazu, Shizuoka 410-0314, Japan
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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This study was partially supported by a Grant-in-Aid for Scientific Research (C) from the Japan Society for the Promotion of Science (JSPS: 16K08169 for Y.S.) and the Sasakawa Scientific Research Grant from The Japan Science Society (2019–3032 for K.B.). XAFS measurements were performed at the Knowledge Hub Aichi of the Aichi Synchrotron Radiation Center (proposal nos. 201705053 and 201802072). We thank technical staff for their kind support with XAFS spectra acquisition. PNR experiments were performed at the BL17 SHARAKU of J-PARC MLF under proposal no. 2017I0017. We thank N. E. Chemcat Corp. for their kind gift of catalysts. We would like to thank Editage (www.editage.jp) for English language editing.

References

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    Pyridine(diimine) Molybdenum-Catalyzed Hydrogenation of Arenes and Hindered Olefins: Insights into Precatalyst Activation and Deactivation Pathways
    Joannou, Matthew V.; Bezdek, Mate J.; Chirik, Paul J.
    ACS Catalysis (2018), 8 (6), 5276-5285CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    Pyridine(diimine) molybdenum bis(olefin) and bis(alkyl) complexes were synthesized, characterized, and examd. for their catalytic activity in the hydrogenation of benzene and a selection of substituted arenes. The molybdenum bis(alkyl) complex (4-tBu-iPrPDI)Mo(CH2SiMe3)2 (iPrPDI = 2,6-(2,6-(C(CH3)2H)2C6H3N=CMe)2C5H3N) exhibited the highest activity for the hydrogenation of benzene, producing cyclohexane in >98% yield at 23 °C under 4 atm of hydrogen after 48 h. Toluene and o-xylene were similarly hydrogenated to their resp. cycloalkanes, with the latter yielding predominantly (79:21 dr) cis-1,2-dimethylcyclohexane. The molybdenum-catalyzed hydrogenation of naphthalene yielded tetralin exclusively, and this selectivity was maintained at higher H2 pressure. At 32 atm of H2, more hindered arenes such as monosubstituted benzenes, biphenyl, and m- and p-xylenes underwent hydrogenation with yields ranging between 20 and >98%. (4-tBu-iPrPDI)Mo(CH2SiMe3)2 was also a competent alkene hydrogenation catalyst, supporting stepwise redn. of benzene to cyclohexadiene and cyclohexene during molybdenum-catalyzed arene hydrogenation. Deuterium labeling studies for the molybdenum-catalyzed hydrogenation of benzene produced numerous isotopologues and stereoisomers of cyclohexane, indicating reversible hydride (deuteride) insertion/β-H(D) elimination, diene/olefin binding, and allylic C-H(D) activation during the reaction. The resting state of the catalyst under neat conditions was established as the η6-benzene complex (iPrPDI)Mo(η6-benzene). Under catalytic conditions, pyridine underwent C-H activation of the 2-position and furan underwent formal C-O oxidative addn. to yield a "metallapyran". Both reactions were identified as important catalyst deactivation pathways for the attempted molybdenum-catalyzed hydrogenation of heteroarenes.
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    .
    (f) Ghosh, S.; Jagirdar, B. R. Effect of the Crystallographic Phase of Ruthenium Nanosponges on Arene and Substituted-Arene Hydrogenation Activity. ChemCatChem 2018, 10, 3086– 3095,  DOI: 10.1002/cctc.201800287
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    3f
    Effect of the Crystallographic Phase of Ruthenium Nanosponges on Arene and Substituted-Arene Hydrogenation Activity
    Ghosh, Sourav; Jagirdar, Balaji R.
    ChemCatChem (2018), 10 (14), 3086-3095CODEN: CHEMK3; ISSN:1867-3880. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Identifying crystal structure sensitivity of a catalyst for a particular reaction is an important issue in heterogeneous catalysis. In this context, the activity of different phases of ruthenium catalysts for benzene hydrogenation has not yet been studied. The synthesis of hcp. and fcc. phases of ruthenium nanosponges by chem. redn. method was described. Redn. of ruthenium chloride using ammonia borane (AB) and tert-butylamine borane (TBAB) as reducing agents gave ruthenium nanosponge in its hcp. phase. However, redn. using sodium borohydride (SB) afforded ruthenium nanosponge in its fcc. phase. The as prepd. hcp. ruthenium nanosponge is catalytically more active compared to the as prepd. fcc. ruthenium nanosponge for hydrogenation of benzene. The hcp. ruthenium nanosponge is thermally stable and recyclable over several cycles. This self-supported hcp. ruthenium nanosponge shows excellent catalytic activity towards hydrogenation of various substituted benzenes. Moreover, the ruthenium nanosponge catalyst was found to bring about selective hydrogenation of arom. cores of phenols and aryl ethers to the resp. alicyclic products without hydrogenolysis of the C-O bond.
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    (g) Ji, P.; Song, Y.; Drake, T.; Veroneau, S. S.; Lin, Z.; Pan, X.; Lin, W. Titanium(III)-Oxo Clusters in a Metal–Organic Framework Support Single-Site Co(II)-Hydride Catalysts for Arene Hydrogenation. J. Am. Chem. Soc. 2018, 140, 433– 440,  DOI: 10.1021/jacs.7b11241
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    3g
    Titanium(III)-Oxo Clusters in a Metal-Organic Framework Support Single-Site Co(II)-Hydride Catalysts for Arene Hydrogenation
    Ji, Pengfei; Song, Yang; Drake, Tasha; Veroneau, Samuel S.; Lin, Zekai; Pan, Xiandao; Lin, Wenbin
    Journal of the American Chemical Society (2018), 140 (1), 433-440CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Titania (TiO2) is widely used in the chem. industry as an efficacious catalyst support, benefiting from its unique strong metal-support interaction. Many proposals have been made to rationalize this effect at the macroscopic level, yet the underlying mol. mechanism is not understood due to the presence of multiple catalytic species on the TiO2 surface. This challenge can be addressed with metal-org. frameworks (MOFs) featuring well-defined metal oxo/hydroxo clusters for supporting single-site catalysts. Herein we report that the Ti8(μ2-O)8(μ2-OH)4 node of the Ti-BDC MOF (MIL-125) provides a single-site model of the classical TiO2 support to enable CoII-hydride-catalyzed arene hydrogenation. The catalytic activity of the supported CoII-hydride is strongly dependent on the redn. of the Ti-oxo cluster, definitively proving the pivotal role of TiIII in the performance of the supported catalyst. This work thus provides a molecularly precise model of Ti-oxo clusters for understanding the strong metal-support interaction of TiO2-supported heterogeneous catalysts.
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    (h) Tang, N.; Cong, Y.; Shang, Q.; Wu, C.; Xu, G.; Wang, X. Coordinatively Unsaturated Al3+ Sites Anchored Subnanometric Ruthenium Catalyst for Hydrogenation of Aromatics. ACS Catal. 2017, 7, 5987– 5991,  DOI: 10.1021/acscatal.7b01816
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    3h
    Coordinatively Unsaturated Al3+ Sites Anchored Subnanometric Ruthenium Catalyst for Hydrogenation of Aromatics
    Tang, Nanfang; Cong, Yu; Shang, Qinghao; Wu, Chuntian; Xu, Guoliang; Wang, Xiaodong
    ACS Catalysis (2017), 7 (9), 5987-5991CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    Single metal atoms and metal clusters have attracted much attention because of their high dispersity, special electronic structures, and uniformity of active sites as heterogeneous catalysts, but it is still challenging to generate stable single atoms and clusters with high metal loadings. Supports play a crucial role in detg. particle morphol. and maintaining dispersion. Herein we synthesize an amorphous alumina with 29% coordinatively unsatd. pentacoordinate Al3+ (Al3+penta) sites, which can anchor atomically dispersed Ru species with 1 wt. % loading. Strong interactions between Ru and Al3+penta centers were detected, resulting in distinct Ru geometric and electronic features. When used in benzene hydrogenation reaction, fairly high specific activity (TOF = 5180 h-1) were obtained. The high catalytic performance is considered closely correlated with the high utilization of special Ru active sites.
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    (i) Cui, X.; Surkus, A.-E.; Junge, K.; Topf, C.; Radnik, J.; Kreyenschulte, C.; Beller, M. Highly selective hydrogenation of arenes using nanostructured ruthenium catalysts modified with a carbon–nitrogen matrix. Nat. Commun. 2016, 7, 11326  DOI: 10.1038/ncomms11326
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    3i
    Highly selective hydrogenation of arenes using nanostructured ruthenium catalysts modified with a carbon-nitrogen matrix
    Cui, Xinjiang; Surkus, Annette-Enrica; Junge, Kathrin; Topf, Christoph; Radnik, Joerg; Kreyenschulte, Carsten; Beller, Matthias
    Nature Communications (2016), 7 (), 11326pp.CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
    Selective hydrogenations of (hetero)arenes represent essential processes in the chem. industry, esp. for the prodn. of polymer intermediates and a multitude of fine chems. Herein, a new type of well-dispersed Ru nanoparticles supported on a nitrogen-doped carbon material obtained from ruthenium chloride and dicyanamide in a facile and scalable method was described. These novel catalysts were stable and display both excellent activity and selectivity in the hydrogenation of arom. ethers, phenols as well as other functionalized substrates to the corresponding alicyclic reaction products. Furthermore, redn. of the arom. core was preferred over hydrogenolysis of the C-O bond in the case of ether substrates. The selective hydrogenation of biomass-derived arenes, such as lignin building blocks, played a pivotal role in the exploitation of novel sustainable feedstocks for chem. prodn. and represents a notoriously difficult transformation up to now.
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    (j) Karakhanov, E. A.; Maximov, A. L.; Zolotukhina, A. V.; Terenina, M. V.; Vutolkina, A. V. Nanoheterogeneous ruthenium-containing catalysts based on dendrimers in the hydrogenation of aromatic compounds under two-phase conditions. Pet. Chem. 2016, 56, 491– 502,  DOI: 10.1134/S0965544116060037
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    3j
    Nanoheterogeneous ruthenium-containing catalysts based on dendrimers in the hydrogenation of aromatic compounds under two-phase conditions
    Karakhanov, E. A.; Maximov, A. L.; Zolotukhina, A. V.; Terenina, M. V.; Vutolkina, A. V.
    Petroleum Chemistry (2016), 56 (6), 491-502CODEN: PHEME4; ISSN:0965-5441. (Pleiades Publishing, Ltd.)
    Nanoheterogeneous catalysts based on ruthenium nanoparticles dispersed in crosslinked dendrimer matrixes with a size of polymer particles of 100-500 nm show high activity in the hydrogenation of arom. compds. under two-phase conditions. The addn. of water to the reaction medium exerts a strong promoting effect on the activity of the catalysts: The turnover frequency increases by a factor of 3-90 depending on the substrate. When bimetallic (PdRu) nanoparticles are incorporated into the catalyst compn., the rate of benzene hydrogenation increases while the rate of transformation of substituted benzenes decreases.
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    (k) Ibrahim, M.; Poreddy, R.; Philippot, K.; Riisager, A.; Garcia-Suarez, E. J. Chemoselective hydrogenation of arenes by PVP supported Rh nanoparticles. Dalton Trans. 2016, 45, 19368– 19373,  DOI: 10.1039/C6DT03668F
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    3k
    Chemoselective hydrogenation of arenes by PVP supported Rh nanoparticles
    Ibrahim, Mahmoud; Poreddy, Raju; Philippot, Karine; Riisager, Anders; Garcia-Suarez, Eduardo J.
    Dalton Transactions (2016), 45 (48), 19368-19373CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
    Polyvinylpyrrolidone-stabilized Rh nanoparticles (RhNPs/PVP) of ca. 2.2 nm in size were prepd. by the hydrogenation of the organometallic complex [Rh(η3-C3H5)3] in the presence of PVP and evaluated as a catalyst in the hydrogenation of a series of arene substrates as well as levulinic acid and Me levulinate. The catalyst showed excellent activity and selectivity towards arom. ring hydrogenation compared to other reported transition metal-based catalysts under mild reaction conditions (room temp. and 1 bar H2). Furthermore, it was shown to be a highly promising catalyst for the hydrogenation of levulinic acid and Me levulinate in water leading to quant. formation of the fuel additive γ-valerolactone under moderate reaction conditions compared to previously reported catalytic systems.
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    (l) Morioka, Y.; Matsuoka, A.; Binder, K.; Knappett, B. R.; Wheatley, A. E. H.; Naka, H. Selective hydrogenation of arenes to cyclohexanes in water catalyzed by chitin-supported ruthenium nanoparticles. Catal. Sci. Technol. 2016, 6, 5801– 5805,  DOI: 10.1039/C6CY00899B
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    3l
    Selective hydrogenation of arenes to cyclohexanes in water catalyzed by chitin-supported ruthenium nanoparticles
    Morioka, Yuna; Matsuoka, Aki; Binder, Kellie; Knappett, Benjamin R.; Wheatley, Andrew E. H.; Naka, Hiroshi
    Catalysis Science & Technology (2016), 6 (15), 5801-5805CODEN: CSTAGD; ISSN:2044-4753. (Royal Society of Chemistry)
    The selective hydrogenation of arom. compds. to cyclohexanes was found to be promoted by chitin-supported ruthenium nanoparticles (Ru/chitin) under near-neutral, aq. conditions without the loss of C-O/C-N linkages at benzylic positions.
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    (m) Pélisson, C.-H.; Denicourt-Nowicki, A.; Roucoux, A. Magnetically Retrievable Rh(0) Nanocomposite as Relevant Catalyst for Mild Hydrogenation of Functionalized Arenes in Water. ACS Sustainable Chem. Eng. 2016, 4, 1834– 1839,  DOI: 10.1021/acssuschemeng.6b00045
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    3m
    Magnetically Retrievable Rh(0) Nanocomposite as Relevant Catalyst for Mild Hydrogenation of Functionalized Arenes in Water
    Pelisson, Carl-Hugo; Denicourt-Nowicki, Audrey; Roucoux, Alain
    ACS Sustainable Chemistry & Engineering (2016), 4 (3), 1834-1839CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
    A Rh0@γ-Fe2O3 nanocomposite was easily prepd. by straightforward deposit of metal nanoparticles on the nonfunctionalized magnetic support through a wet impregnation method. This nanomaterial proved to be highly active and magnetically retrievable in room-temp. hydrogenation of various arenes under atm. hydrogen pressure in neat water. The catalytic applications were extended to the selective redn. of nitroarenes into aniline, a relevant synthon for industrial applications, and to the dechlorination of chloroarenes, which could be of great interest for wastewater treatment. Finally, these Rh0@γ-Fe2O3 nanocomposites were compared to their Pd analogs, thus affording complementary catalytic activities.
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    (n) Shi, J.; Zhao, M.; Wang, Y.; Fu, J.; Lu, X.; Hou, Z. Upgrading of aromatic compounds in bio-oil over ultrathin graphene encapsulated Ru nanoparticles. J. Mater. Chem. A 2016, 4, 5842– 5848,  DOI: 10.1039/C6TA01317A
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    Upgrading of aromatic compounds in bio-oil over ultrathin graphene encapsulated Ru nanoparticles
    Shi, Juanjuan; Zhao, Mengsi; Wang, Yingyu; Fu, Jie; Lu, Xiuyang; Hou, Zhaoyin
    Journal of Materials Chemistry A: Materials for Energy and Sustainability (2016), 4 (16), 5842-5848CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
    Fast pyrolysis of biomass for bio-oil prodn. is a direct route to renewable liq. fuels, but raw bio-oil must be upgraded in order to remove easily polymd. compds. (such as phenols and furfurals). Herein, a synthesis strategy for graphene encapsulated Ru nanoparticles (NPs) on carbon sheets (denoted as Ru@G-CS) and their excellent performance for the upgrading of raw bio-oil were reported. Ru@G-CS composites were prepd. via the direct pyrolysis of mixed glucose, melamine and RuCl3 at varied temps. (500-800 °C). Characterization indicated that very fine Ru NPs (2.5 ± 1.0 nm) that were encapsulated within 1-2 layered N-doped graphene were fabricated on N-doped carbon sheets (CS) in Ru@G-CS-700 (pyrolysis at 700 °C). And the Ru@G-CS-700 composite was highly active and stable for hydrogenation of unstable components in bio-oil (31 samples including phenols, furfurals and aroms.) even in aq. media under mild conditions. This work provides a new protocol to the utilization of biomass, esp. for the upgrading of bio-oil.
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    (o) Sun, B.; Süss-Fink, G. Ruthenium-catalyzed hydrogenation of aromatic amino acids in aqueous solution. J. Organomet. Chem. 2016, 81– 86,  DOI: 10.1016/j.jorganchem.2015.09.011
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    Ruthenium-catalyzed hydrogenation of aromatic amino acids in aqueous solution
    Sun, Bing; Suss-Fink, Georg
    Journal of Organometallic Chemistry (2016), 812 (), 81-86CODEN: JORCAI; ISSN:0022-328X. (Elsevier B.V.)
    A catalyst contg. metallic ruthenium nanoparticles intercalated in hectorite (nanoRu@hectorite) was found to catalyze the hydrogenation of arom. amino acids in aq. soln. Thus, L-phenylalanine and L-phenylglycine can be converted exclusively into the corresponding L-cyclohexyl amino acids with retention of chirality under mild conditions (60 °C, 40 bar), conversion and selectivity being superior to 99%. The catalyst can be recycled and reused at least three times without loss in activity and selectivity.
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    (p) Baghbanian, S. M.; Farhang, M.; Vahdat, S. M.; Tajbakhsh, M. Hydrogenation of arenes, nitroarenes, and alkenes catalyzed by rhodium nanoparticles supported on natural nanozeolite clinoptilolite. J. Mol. Catal. A: Chem. 2015, 128– 136,  DOI: 10.1016/j.molcata.2015.06.029
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    Hydrogenation of arenes, nitroarenes, and alkenes catalyzed by rhodium nanoparticles supported on natural nanozeolite clinoptilolite
    Baghbanian, Seyed Meysam; Farhang, Maryam; Vahdat, Seyed Mohammad; Tajbakhsh, Mahmood
    Journal of Molecular Catalysis A: Chemical (2015), 407 (), 128-136CODEN: JMCCF2; ISSN:1381-1169. (Elsevier B.V.)
    Nanozeolite clinoptilolite supported rhodium nanoparticles (Rh/NZ-CP) has been prepd. and characterized by a variety of techniques, including XRD, BET, TEM, EDX, ICP-OES and XPS anal. This nanomaterial contains 2 wt% Rh in the range of 5-20 nm metallic nanoparticles distributed on nanozeolite. The catalytic performance of Rh/NZ-CP was evaluated by the hydrogenation of arenes, nitroarenes, and alkenes under moderate reaction conditions. The prepd. nanocatalyst can be facilely recovered and reused many times without significant decrease in activity and selectivity. The high catalytic activity, thermal stability and reusability, simple recovery and eco-friendly nature make present catalyst as a unique catalytic system, which is particularly attractive in green chem.
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    (q) Martínez-Prieto, L. M.; Urbaneja, C.; Palma, P.; Cámpora, J.; Philippot, K.; Chaudret, B. A betaine adduct of N-heterocyclic carbene and carbodiimide, an efficient ligand to produce ultra-small ruthenium nanoparticles. Chem. Commun. 2015, 51, 4647– 4650,  DOI: 10.1039/C5CC00211G
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    3q
    A betaine adduct of N-heterocyclic carbene and carbodiimide, an efficient ligand to produce ultra-small ruthenium nanoparticles
    Martinez-Prieto, L. M.; Urbaneja, C.; Palma, P.; Campora, J.; Philippot, K.; Chaudret, B.
    Chemical Communications (Cambridge, United Kingdom) (2015), 51 (22), 4647-4650CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    The betaine adduct of N-heterocyclic carbene and carbodiimide ICy+·4-MeC6H4N:CN-C6H4Me-4 (ICy = 1,3-dicyclohexyl-2-imidazolylidene) was found to be a very efficient ligand and stabilizing agent to prep. very small (1-1.3 nm) ruthenium nanoparticles (RuNPs). The ligand is attached to ruthenium cluster surface by its carbodiimide nitrogens, carrying a delocalized neg. charge. The coordination of the ligand on the metal surface takes place through the carbodiimide moiety. The resulting RuNPs led to decarbonylation of THF and showed size selectivity for styrene hydrogenation.
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    (r) Kang, X.; Zhang, J.; Shang, W.; Wu, T.; Zhang, P.; Han, B.; Wu, Z.; Mo, G.; Xing, X. One-Step Synthesis of Highly Efficient Nanocatalysts on the Supports with Hierarchical Pores Using Porous Ionic Liquid-Water Gel. J. Am. Chem. Soc. 2014, 136, 3768– 3771,  DOI: 10.1021/ja5001517
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    3r
    One-Step Synthesis of Highly Efficient Nanocatalysts on the Supports with Hierarchical Pores Using Porous Ionic Liquid-Water Gel
    Kang, Xinchen; Zhang, Jianling; Shang, Wenting; Wu, Tianbin; Zhang, Peng; Han, Buxing; Wu, Zhonghua; Mo, Guang; Xing, Xueqing
    Journal of the American Chemical Society (2014), 136 (10), 3768-3771CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Stable porous ionic liq.-water gel induced by inorg. salts was created for the first time. The porous gel was used to develop a one-step method to synthesize supported metal nanocatalysts. Au/SiO2, Ru/SiO2, Pd/Cu(2-pymo)2 metal-org. framework (Cu-MOF), and Au/polyacrylamide (PAM) were synthesized, in which the supports had hierarchical meso- and macropores, the size of the metal nanocatalysts could be small (<1 nm), and the size distribution was narrow even when the metal loading amt. was as high as 8 wt. %. The catalysts were extremely active, selective, and stable for oxidative esterification of benzyl alc. to Me benzoate, benzene hydrogenation to cyclohexane, and oxidn. of benzyl alc. to benzaldehyde because they combined the advantages of the nanocatalysts of small size and hierarchical porosity of the supports. In addn., this method is simple.
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    (s) Maegawa, T.; Akashi, A.; Yaguchi, K.; Iwasaki, Y.; Shigetsura, M.; Monguchi, Y.; Sajiki, H. Efficient and Practical Arene Hydrogenation by Heterogeneous Catalysts under Mild Conditions. Chem. - Eur. J. 2009, 15, 6953– 6963,  DOI: 10.1002/chem.200900361
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    Efficient and Practical Arene Hydrogenation by Heterogeneous Catalysts under Mild Conditions
    Maegawa, Tomohiro; Akashi, Akira; Yaguchi, Kiichiro; Iwasaki, Yohei; Shigetsura, Masahiro; Monguchi, Yasunari; Sajiki, Hironao
    Chemistry - A European Journal (2009), 15 (28), 6953-6963, S6953/1-S6953/85CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    An efficient and practical arene hydrogenation procedure based on the use of heterogeneous platinum group catalysts has been developed. Rh/C is the most effective catalyst for the hydrogenation of the arom. ring, which can be conducted in iPrOH under neutral conditions and at ordinary to medium H2 pressures (<10 atm). A variety of arenes such as alkylbenzenes, benzoic acids, pyridines, furans, are hydrogenated to the corresponding cyclohexyl and heterocyclic compds. in good to excellent yields. The use of Ru/C, less expensive than Rh/C, affords an effective and practical method for the hydrogenation of arenes including phenols. Both catalysts can be reused several times after simple filtration without any significant loss of catalytic activity.
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    (t) Maegawa, T.; Akashi, A.; Sajiki, H. A Mild and Facile Method for Complete Hydrogenation of Aromatic Nuclei in Water. Synlett 2006, 9, 1440– 1442,  DOI: 10.1055/s-2006-939719
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  4. 4

    For selected papers, see:

    (a) Jie, X.; Gonzalez-Cortes, S.; Xiao, T.; Wang, J.; Yao, B.; Slocombe, D. R.; Al-Megren, H. A.; Dilworth, J. R.; Thomas, J. M.; Edwards, P. P. Rapid Production of High-Purity Hydrogen Fuel through Microwave-Promoted Deep Catalytic Dehydrogenation of Liquid Alkanes with Abundant Metals. Angew. Chem., Int. Ed. 2017, 56, 10170– 10173,  DOI: 10.1002/anie.201703489
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    Rapid Production of High-Purity Hydrogen Fuel through Microwave-Promoted Deep Catalytic Dehydrogenation of Liquid Alkanes with Abundant Metals
    Jie, Xiangyu; Gonzalez-Cortes, Sergio; Xiao, Tiancun; Wang, Jiale; Yao, Benzhen; Slocombe, Daniel R.; Al-Megren, Hamid A.; Dilworth, Jonathan R.; Thomas, John M.; Edwards, Peter P.
    Angewandte Chemie, International Edition (2017), 56 (34), 10170-10173CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Hydrogen as an energy carrier promises a sustainable energy revolution. However, one of the greatest challenges for any future hydrogen economy is the necessity for large scale hydrogen prodn. not involving concurrent CO2 prodn. The high intrinsic hydrogen content of liq.-range alkane hydrocarbons (including diesel) offers a potential route to CO2-free hydrogen prodn. through their catalytic deep dehydrogenation. We report here a means of rapidly liberating high-purity hydrogen by microwave-promoted catalytic dehydrogenation of liq. alkanes using Fe and Ni particles supported on silicon carbide. A H2 prodn. selectivity from all evolved gases of some 98 %, is achieved with less than a fraction of a percent of adventitious CO and CO2. The major co-product is solid, elemental carbon.
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    .
    (b) Gonzalez-Cortes, S.; Slocombe, D. R.; Xiao, T.; Aldawsari, A.; Yao, B.; Kuznetsov, V. L.; Leberti, E.; Kirkland, A. I.; Alkinani, M. S.; Al-Megren, H. A.; Thomas, J. M.; Edwards, P. P. Wax: A benign hydrogen-storage material that rapidly releases H2-rich gases through microwave-assisted catalytic decomposition. Sci. Rep. 2016, 6, 35315  DOI: 10.1038/srep35315
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    4b
    Wax: A benign hydrogen-storage material that rapidly releases H2-rich gases through microwave-assisted catalytic decomposition
    Gonzalez-Cortes, S.; Slocombe, D. R.; Xiao, T.; Aldawsari, A.; Yao, B.; Kuznetsov, V. L.; Liberti, E.; Kirkland, A. I.; Alkinani, M. S.; Al-Megren, H. A.; Thomas, J. M.; Edwards, P. P.
    Scientific Reports (2016), 6 (), 35315CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)
    Hydrogen is often described as the fuel of the future, esp. for application in hydrogen powered fuel-cell vehicles (HFCV's). However, its widespread implementation in this role has been thwarted by the lack of a lightwt., safe, on-board hydrogen storage material. Here we show that benign, readily-available hydrocarbon wax is capable of rapidly releasing large amts. of hydrogen through microwave-assisted catalytic decompn. This discovery offers a new material and system for safe and efficient hydrogen storage and could facilitate its application in a HFCV. Importantly, hydrogen storage materials made of wax can be manufd. through completely sustainable processes utilizing biomass or other renewable feedstocks.
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    (c) Susanti, R. F.; Dianningrum, L. W.; Yum, T.; Kim, Y.; Lee, Y.-W.; Kim, J. High-yield hydrogen production by supercritical water gasification of various feedstocks: Alcohols, glucose, glycerol and long-chain alkanes. Chem. Eng. Res. Des. 2014, 92, 1834– 1844,  DOI: 10.1016/j.cherd.2014.01.003
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    4c
    High-yield hydrogen production by supercritical water gasification of various feedstocks: Alcohols, glucose, glycerol and long-chain alkanes
    Susanti, Ratna F.; Dianningrum, Laras W.; Yum, Taewoo; Kim, Yunje; Lee, Youn-Woo; Kim, Jaehoon
    Chemical Engineering Research and Design (2014), 92 (10), 1834-1844CODEN: CERDEE; ISSN:1744-3563. (Elsevier B.V.)
    Continuous supercrit. water gasification (SCWG) of various feedstocks of C1-C16 was conducted to produce hydrogen-rich gas. These feedstocks represent model compds. of biomass such as methanol/ethanol (alc.-type), glucose and glycerol (byproducts of biodiesel synthesis), and model compds. of petroleum fuels such as iso-octane/n-octane (gasoline), n-decane/n-dodecane (jet fuels) and n-hexadecane (diesel). Almost complete gasification of all the feedstocks was achieved at 25 MPa, 740 °C and 10 wt% with low total org. carbon values of their liq. effluents. The hydrogen gas yields of each feedstock were very similar to the theor. equil. yields estd. by Gibbs free energy minimization. SCWG at different gasification temps. (650 and 740 °C) and concns. (10 and 20 wt%) revealed that methanol and ethanol (alcs.), the simple oxygenated hydrocarbons, were easier to be gasified, producing negligible amts. of liq. products, when compared with long-chain hydrocarbons (iso-octane and n-decane) under the identical conditions. When the feedstock concn. was increased from 10 to 20 wt%, the equil. hydrogen ratio from iso-octane gasification decreased from 1.02 to 0.79 while that of n-decane increased from 1.12 to 1.50, implying that a branched hydrocarbon may be more resistant to gasification in supercrit. water.
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    (d) Ahmed, S.; Aitani, A.; Rahman, F.; Al-Dawood, A.; Al-Muhaish, F. Decomposition of hydrocarbons to hydrogen and carbon. Appl. Catal., A 2009, 359, 1– 24,  DOI: 10.1016/j.apcata.2009.02.038
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    4d
    Decomposition of hydrocarbons to hydrogen and carbon
    Ahmed, Shakeel; Aitani, Abdullah; Rahman, Faizur; Al-Dawood, Ali; Al-Muhaish, Fahad
    Applied Catalysis, A: General (2009), 359 (1-2), 1-24CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
    A review of technologies and catalysts pertaining to the catalytic decompn. of hydrocarbons for the CO2-free generation of H for fuel cell applications through single-step cracking (decompn., decarbonization, dehydrogenation, pyrolysis, splitting, or dissocn.) of hydrocarbons. The options for hydrocarbon decompn. to H and C are discussed and categorized. This decompn. helps to reduce green house gases by co-producing valuable C products such as C black or graphite-like C (C nanotubes or C filaments). The catalytic approach comprises metal and C-based catalysts while plasma-based decompn. depends on thermal or nonthermal methods. Almost all the proposed processes are applicable to a variety of gaseous and liq. hydrocarbon fuels and some of these processes can potentially produce a stream of high-purity H. There have been successful attempts to use catalysts to decrease the max. temp. of the thermal decompn. of hydrocarbons. Common catalysts used are noble and transition metals such as Ni, Fe, Pd, Co and Mo supported on high surface-area ceramic substrates such as Al2O3 and SiO2. Several publications disclose the use of C-based materials as catalysts for decompn. of hydrocarbons into H2 and C. Other non-catalytic decompn. methods include non-thermal low-temp. plasmas such as RF, d.c. generators, microwave plasmatrons and arc plasma jet.
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  5. 5
    (a) Espro, C.; Gumina, B.; Szumelda, T.; Paone, E.; Mauriello, F. Catalytic transfer hydrogenolysis as an effective tool for the reductive upgrading of cellulose, hemicellulose, lignin, and their derived molecules. Catalysts 2018, 3, 313,  DOI: 10.3390/catal8080313
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    (b) Wang, D.; Astruc, D. The golden age of transfer hydrogenation. Chem. Rev. 2015, 115, 6621– 6686,  DOI: 10.1021/acs.chemrev.5b00203
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    5b
    The Golden Age of Transfer Hydrogenation
    Wang, Dong; Astruc, Didier
    Chemical Reviews (Washington, DC, United States) (2015), 115 (13), 6621-6686CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review on transfer hydrogenation using transition metal catalysts and organocatalysts.
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    (c) Gilkey, M. J.; Xu, B. Heterogeneous catalytic transfer hydrogenation as an effective pathway in biomass upgrading. ACS Catal. 2016, 6, 1420– 1436,  DOI: 10.1021/acscatal.5b02171
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    5c
    Heterogeneous Catalytic Transfer Hydrogenation as an Effective Pathway in Biomass Upgrading
    Gilkey, Matthew J.; Xu, Bingjun
    ACS Catalysis (2016), 6 (3), 1420-1436CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    A review is given. Reducing O content in biomass-derived feedstocks via hydrodeoxygenation (HDO) is a key step in their upgrading to fuels and valuable chems. Org. mols., e.g., alcs. and formic acid, can donate H to reduce the substrate in a process called catalytic transfer hydrogenation (CTH). Although it is practiced far less frequently than mol.-hydrogen-based HDO processes, CTH has been proven to be an efficient and selective strategy in biomass upgrading in the last two decades. We present a selective review of recent progress made in the upgrade of biomass-derived feedstocks through heterogeneous CTH, with a focus on the mechanistic interpretation. Hydrogenation and cleavage of C=O and C-O bonds, resp., are the 2 main categories of reactions discussed, owing to their importance in the HDO of biomass-derived feedstocks. On acid-base catalysts, Lewis acid-base pair sites, rather than a single acid or base site, mediate hydrogenation of carbonyl groups with alcs. as the H donor. While acid-base catalysts typically only catalyze the hydrogenation of carbonyl groups with alcs. as the H donor, metal-based catalysts are able to mediate both hydrogenation and hydrogenolysis reactions with either alcs. or formic acid. Several model reactions involving platform chems. in biomass upgrading, e.g., 5-hydroxymethylfurfural, levulinic acid, and glycerol, are used in the discussion to illustrate general trends. Because alcs. are typically both the H donor and the solvent, the donor and solvent effects are intertwined. Therefore, solvent effects are discussed primarily in the context of sugar isomerization and reactions with formic acid as the H donor, in which the solvent and H donor are 2 sep. species. Current challenges and opportunities of future research to develop CTH into a competitive and complementary strategy of the conventional mol.-H-based processes are also discussed.
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  6. 6
    (a) Paone, E.; Espro, C.; Pietropaolo, R.; Mauriello, F. Selective arene production form transfer hydrogenolysis of benzyl phenyl ether promoted by the coprecipitated Pd/Fe3O4 catalyst. Catal. Sci. Technol. 2016, 6, 7937– 7941,  DOI: 10.1039/C6CY01626J
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    6a
    Selective arene production from transfer hydrogenolysis of benzyl phenyl ether promoted by a co-precipitated Pd/Fe3O4 catalyst
    Paone, E.; Espro, C.; Pietropaolo, R.; Mauriello, F.
    Catalysis Science & Technology (2016), 6 (22), 7937-7941CODEN: CSTAGD; ISSN:2044-4753. (Royal Society of Chemistry)
    The catalytic transfer hydrogenolysis of benzyl Ph ether has been investigated using Pd/Fe3O4 as a heterogeneous catalyst and 2-propanol as a H-donor. After 90 min at 240°, the cleavage of the ether C-O bond occurs as the only reaction route without hydrogenation of the arom. ring.
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    (b) Espro, C.; Gumina, B.; Paone, E.; Mauriello, F. Upgrading Lignocellulosic Biomasses: Hydrogenolysis of Platform Derived Molecules Promoted by Heterogeneous Pd-Fe Catalysts. Catalysts 2017, 7, 78,  DOI: 10.3390/catal7030078
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    6b
    Upgrading lignocellulosic biomasses: hydrogenolysis of platform derived molecules promoted by heterogeneous Pd-Fe catalysts
    Espro, Claudia; Gumina, Bianca; Paone, Emilia; Mauriello, Francesco
    Catalysts (2017), 7 (3), 78/1-78/36CODEN: CATACJ; ISSN:2073-4344. (MDPI AG)
    This review provides an overview of heterogeneous bimetallic Pd-Fe catalysts in the C-C and C-O cleavage of platform mols. such as C2-C6 polyols, furfural, phenol derivs. and arom. ethers that are all easily obtainable from renewable cellulose, hemicellulose and lignin (the major components of lignocellulosic biomasses). The interaction between palladium and iron affords bimetallic Pd-Fe sites (ensemble or alloy) that were found to be very active in several sustainable reactions including hydrogenolysis, catalytic transfer hydrogenolysis (CTH) and aq. phase reforming (APR) that will be highlighted. This contribution concs. also on the different synthetic strategies (incipient wetness impregnation, deposition-pptn., co-pptn.) adopted for the prepn. of heterogeneous Pd-Fe systems as well as on the main characterization techniques used (XRD, TEM, H2-TPR, XPS and EXAFS) in order to elucidate the key factors that influence the unique catalytic performances obsd.
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  7. 7
    (a) Sawama, Y.; Morita, K.; Yamada, T.; Nagata, S.; Yabe, Y.; Monguchi, Y.; Sajiki, H. Rhodium-on-carbon catalyzed hydrogen scavenger- and oxidant-free dehydrogenation of alcohols in aqueous media. Green Chem. 2014, 16, 3439– 3443,  DOI: 10.1039/c4gc00434e
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    7a
    Rhodium-on-carbon catalyzed hydrogen scavenger- and oxidant-free dehydrogenation of alcohols in aqueous media
    Sawama, Yoshinari; Morita, Kosuke; Yamada, Tsuyoshi; Nagata, Saori; Yabe, Yuki; Monguchi, Yasunari; Sajiki, Hironao
    Green Chemistry (2014), 16 (7), 3439-3443CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
    The efficient and catalytic dehydrogenation of alcs. is a clean approach for prepg. carbonyl compds. accompanied only by the generation of hydrogen gas. We have accomplished the heterogeneous rhodium-on-carbon catalyzed dehydrogenation of secondary, as well as primary, alcs. to the corresponding ketones and carboxylic acids in water under basic conditions.
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    (b) Sawama, Y.; Morita, K.; Asai, S.; Kozawa, M.; Tadokoro, S.; Nakajima, J.; Monguchi, Y.; Sajiki, H. Palladium on Carbon-Catalyzed Aqueous Transformation of Primary Alcohols to Carboxylic Acids Based on Dehydrogenation under Mildly Reduced Pressure. Adv. Synth. Catal. 2015, 357, 1205– 1210,  DOI: 10.1002/adsc.201401123
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    7b
    Palladium-on-Carbon-Catalyzed Aqueous Transformation of Primary Alcohols to Carboxylic Acids Based on Dehydrogenation under Mildly Reduced Pressure
    Sawama, Yoshinari; Morita, Kosuke; Asai, Shota; Kozawa, Masami; Tadokoro, Shinsuke; Nakajima, Junichi; Monguchi, Yasunari; Sajiki, Hironao
    Advanced Synthesis & Catalysis (2015), 357 (6), 1205-1210CODEN: ASCAF7; ISSN:1615-4150. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The catalytic dehydrogenation of alcs. to carbonyl products is a green sustainable oxidn. with no prodn. of waste except for hydrogen, which is an energy source. Addnl., a reusable heterogeneous catalyst is valuable from the viewpoint of process chem. and water is a green solvent. The palladium on carbon (Pd/C)-catalyzed dehydrogenation of primary alcs. to carboxylic acids in water was accomplished under a mildly reduced pressure (800 hPa). The reduced pressure was easily controlled by the vacuum controller of the rotary evaporator to remove the excess of generated hydrogen, which causes the redn. (reverse reaction) of aldehydes to alcs. (starting materials) and other undesirable side reactions. The present method is applicable to the reaction of various aliph. and benzylic alcs. to the corresponding carboxylic acids, and the Pd/C can be reused at least 5 times.
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  8. 8
    (a) Yasukawa, N.; Yokoyama, H.; Masuda, M.; Monguchi, Y.; Sajiki, H.; Sawama, Y. Highly-functionalized arene synthesis based on palladium on carbon-catalyzed aqueous dehydrogenation of cyclohexadienes and cyclohexenes. Green Chem. 2018, 20, 1213– 1217,  DOI: 10.1039/C7GC03819D
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    8a
    Highly-functionalized arene synthesis based on palladium on carbon-catalyzed aqueous dehydrogenation of cyclohexadienes and cyclohexenes
    Yasukawa, Naoki; Yokoyama, Hiroki; Masuda, Masahiro; Monguchi, Yasunari; Sajiki, Hironao; Sawama, Yoshinari
    Green Chemistry (2018), 20 (6), 1213-1217CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
    Transition metal-catalyzed dehydrogenation was a clean oxidn. method requiring no addnl. oxidants. A heterogeneous Pd/C-catalyzed aq. dehydrogenation of 1,4-cyclohexadienes and cyclohexenes to give the corresponding highly-functionalized arenes was described. Furthermore, various arenes were efficiently constructed in a one-pot manner via a Diels-Alder reaction followed by dehydrogenation.
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    .
    (b) Ichikawa, T.; Matsuo, T.; Tachikawa, T.; Yamada, T.; Yoshimura, T.; Yoshimura, M.; Takagi, Y.; Sawama, Y.; Sugiyama, J.; Monguchi, Y.; Sajiki, H. Microwave-Mediated Site-Selective Heating of Spherical-Carbon-Bead-Supported Platinum for the Continuous, Efficient Catalytic Dehydrogenative Aromatization of Saturated Cyclic Hydrocarbons. ACS Sustainable Chem. Eng. 2019, 7, 3052– 3061,  DOI: 10.1021/acssuschemeng.8b04655
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    8b
    Microwave-Mediated Site-Selective Heating of Spherical-Carbon-Bead-Supported Platinum for the Continuous, Efficient Catalytic Dehydrogenative Aromatization of Saturated Cyclic Hydrocarbons
    Ichikawa, Tomohiro; Matsuo, Tomohiro; Tachikawa, Takumu; Yamada, Tsuyoshi; Yoshimura, Takeo; Yoshimura, Masatoshi; Takagi, Yukio; Sawama, Yoshinari; Sugiyama, Jun-ichi; Monguchi, Yasunari; Sajiki, Hironao
    ACS Sustainable Chemistry & Engineering (2019), 7 (3), 3052-3061CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
    A microwave (MW)-assisted method for the continuous prodn. of hydrogen from methylcyclohexane using platinum on spherical carbon beads has been developed, and its application to the efficient dehydrogenative aromatization of fully satd. cyclic alkanes, including piperidines as representative heterocycles, has been studied. Effective dehydrogenation was achieved by the construction of a highly intense energy field, which acted as a reactive site, on the irradn. of the carbon beads (CB) support. The reaction could be carried out with only 10-W single-frequency MWs. The catalyst system could be used continuously for at least 12 h without any loss of catalyst activity. Dehydrogenative aromatization could also be catalyzed and simple cyclohexane derivs., as well as piperidine derivs. as representative N-heterocyclic alkanes, were tested.
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  9. 9
    (a) Sawama, Y.; Niikawa, M.; Yabe, Y.; Goto, R.; Kawajiri, T.; Marumoto, T.; Takahashi, T.; Itoh, M.; Sasai, Y.; Yamauchi, Y.; Kondo, S.; Kuzuya, M.; Itoh, M.; Monguchi, Y.; Sajiki, H. Stainless-Steel-Mediated Quantitative Hydrogen Generation from Water under Ball Milling Conditions. ACS Sustainable Chem. Eng. 2015, 3, 683– 689,  DOI: 10.1021/sc5008434
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    9a
    Stainless-Steel-Mediated Quantitative Hydrogen Generation from Water under Ball Milling Conditions
    Sawama, Yoshinari; Niikawa, Miki; Yabe, Yuki; Goto, Ryota; Kawajiri, Takahiro; Marumoto, Takahisa; Takahashi, Tohru; Itoh, Miki; Kimura, Yuuichi; Sasai, Yasushi; Yamauchi, Yukinori; Kondo, Shin-ichi; Kuzuya, Masayuki; Monguchi, Yasunari; Sajiki, Hironao
    ACS Sustainable Chemistry & Engineering (2015), 3 (4), 683-689CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
    A robust and quant. gaseous H generation method was developed in an effort to achieve efficient H2 generation derived from H2O. The present reaction could be achieved by a simple ball friction (milling) reaction of H2O using a planetary ball mill machine with a stainless-steel vessel and balls. It was mediated by metals as an element of stainless steel of the ball mill and also promoted by mechanochem. processing.
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    .
    (b) Sawama, Y.; Kawajiri, T.; Niikawa, M.; Goto, R.; Yabe, Y.; Takahashi, T.; Marumoto, T.; Itoh, M.; Kimura, Y.; Monguchi, Y.; Kondo, S.; Sajiki, H. Stainless-Steel Ball-Milling Method for Hydro-/Deutero-genation using H2O/D2O as a Hydrogen/Deuterium Source. ChemSusChem 2015, 8, 3773– 3776,  DOI: 10.1002/cssc.201501019
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    9b
    Stainless-Steel Ball-Milling Method for Hydro-/Deutero-genation using H2O/D2O as a Hydrogen/Deuterium Source
    Sawama, Yoshinari; Kawajiri, Takahiro; Niikawa, Miki; Goto, Ryota; Yabe, Yuki; Takahashi, Tohru; Marumoto, Takahisa; Itoh, Miki; Kimura, Yuuichi; Monguchi, Yasunari; Kondo, Shin-ichi; Sajiki, Hironao
    ChemSusChem (2015), 8 (22), 3773-3776CODEN: CHEMIZ; ISSN:1864-5631. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A one-pot continuous-flow method for hydrogen (deuterium) generation and subsequent hydrogenation (deuterogenation) was developed using a stainless-steel (SUS304)-mediated ball-milling approach. SUS304, esp. zero-valent Cr and Ni as constituents of the SUS304, and mechanochem. processing played crucial roles in the development of the reactions.
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    .
    (c) Sawama, Y.; Yasukawa, N.; Ban, K.; Goto, R.; Niikawa, M.; Monguchi, Y.; Itoh, M.; Sajiki, H. Stainless Steel-Mediated Hydrogen Generation from Alkanes and Diethyl Ether and Its Application for Arene Reduction. Org. Lett. 2018, 20, 2892– 2896,  DOI: 10.1021/acs.orglett.8b00931
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    9c
    Stainless Steel-Mediated Hydrogen Generation from Alkanes and Diethyl Ether and Its Application for Arene Reduction
    Sawama, Yoshinari; Yasukawa, Naoki; Ban, Kazuho; Goto, Ryota; Niikawa, Miki; Monguchi, Yasunari; Itoh, Miki; Sajiki, Hironao
    Organic Letters (2018), 20 (10), 2892-2896CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
    Hydrogen gas can be generated from simple alkanes (e.g., n-pentane, n-hexane, etc.) and di-Et ether (Et2O) by mechanochem. energy using a planetary ball mill (SUS304, Fritsch Pulverisette 7), and the use of stainless steel balls and vessel is an important factor to generate the hydrogen. The redn. of org. compds. was also accomplished using the in-situ-generated hydrogen. While the use of pentane as the hydrogen source facilitated the redn. of the olefin moieties, the arene redn. could proceed using Et2O. Within the components (Fe, Cr, Ni, etc.) of the stainless steel, Cr was the metal factor for the hydrogen generation from the alkanes and Et2O, and Ni metal played the role of the hydrogenation catalyst.
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  10. 10
    (a) Sawama, Y.; Yabe, Y.; Shigetsura, M.; Yamada, T.; Nagata, S.; Fujiwara, Y.; Maegawa, T.; Monguchi, Y.; Sajiki, H. Platinum on Carbon-Catalyzed Hydrodefluorination of Fluoroarenes using Isopropyl Alcohol-Water-Sodium Carbonate Combination. Adv. Synth. Catal. 2012, 354, 777– 782,  DOI: 10.1002/adsc.201100927
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    10a
    Platinum on Carbon-Catalyzed Hydrodefluorination of Fluoroarenes using Isopropyl Alcohol-Water-Sodium Carbonate Combination
    Sawama, Yoshinari; Yabe, Yuki; Shigetsura, Masahiro; Yamada, Tsuyoshi; Nagata, Saori; Fujiwara, Yuta; Maegawa, Tomohiro; Monguchi, Yasunari; Sajiki, Hironao
    Advanced Synthesis & Catalysis (2012), 354 (5), 777-782CODEN: ASCAF7; ISSN:1615-4150. (Wiley-VCH Verlag GmbH & Co. KGaA)
    We have developed a platinum on carbon-iso-Pr alc.-catalyzed and widely applicable defluorination method for fluoroarenes, e.g., 4-FC6H4Ph, and the addn. of water and sodium carbonate efficiently accelerated the reaction. The defluorination readily occurred under the reaction conditions in comparison with the dehalogenation of other arom. halides (fluorine>chlorine>bromine»iodine).
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    .
    (b) Sawama, Y.; Mori, M.; Yamada, T.; Monguchi, Y.; Sajiki, H. Hydrogen Self-Sufficient Arene Reduction to Cyclohexane Derivatives Using a Combination of Platinum on Carbon and 2-Propanol. Adv. Synth. Catal. 2015, 357, 3667– 3670,  DOI: 10.1002/adsc.201500263
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    10b
    Hydrogen Self-Sufficient Arene Reduction to Cyclohexane Derivatives Using a Combination of Platinum on Carbon and 2-Propanol
    Sawama, Yoshinari; Mori, Misato; Yamada, Tsuyoshi; Monguchi, Yasunari; Sajiki, Hironao
    Advanced Synthesis & Catalysis (2015), 357 (16-17), 3667-3670CODEN: ASCAF7; ISSN:1615-4150. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Various arenes have been hydrogenated using platinum on carbon in a 2-propanol-aq. mixed solvent at 100 °C without the addn. of flammable hydrogen gas to give the corresponding cyclohexane derivs. 2-Propanol plays a role as an efficient hydrogen source based on the platinum on carbon-catalyzed dehydrogenation.
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  11. 11
    (a) Wang, H.; Krier, J. M.; Zhu, Z.; Melaet, G.; Wang, Y.; Kennedy, G.; Alayoglu, S.; An, K.; Somorjai, G. A. Promotion of Hydrogenation of Organic Molecules by Incorporating Iron into Platinum Nanoparticle Catalysts: Displacement of Inactive Reaction Intermediates. ACS Catal. 2013, 3, 2371– 2375,  DOI: 10.1021/cs400579j
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    11a
    Promotion of Hydrogenation of Organic Molecules by Incorporating Iron into Platinum Nanoparticle Catalysts: Displacement of Inactive Reaction Intermediates
    Wang, Hailiang; Krier, James M.; Zhu, Zhongwei; Melaet, Gerome; Wang, Yihai; Kennedy, Griffin; Alayoglu, Selim; An, Kwangjin; Somorjai, Gabor A.
    ACS Catalysis (2013), 3 (10), 2371-2375CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    We characterize the surface chem. states of reactants and catalysts under reaction conditions to elucidate the compn. effect of platinum-iron bimetallic nanoparticles on catalytic hydrogenation of org. mols. The catalytic hydrogenation of ethylene is drastically accelerated on the surface of 2 nm PtFe bimetallic nanoparticles as compared to pure Pt. Sum frequency generation (SFG) vibrational spectroscopy indicates that incorporation of Fe into Pt nanoparticle catalysts weakens the adsorption of ethylidyne, an inactive spectator species, on the catalyst surface. Similarly, the turnover frequency of cyclohexene hydrogenation is also significantly enhanced by incorporating Fe into Pt nanoparticle catalysts. Ambient-pressure XPS (AP-XPS) reveals the surface compn. and oxidn. states of the PtFe nanoparticles under reaction conditions. The oxidn. state distribution of Fe responded to the gas atm. and the probing depth, whereas the Pt remained largely metallic in all probing conditions. This work represents a mol. level correlation between catalyst structure and catalytic performance.
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    .
    (b) Liu, Z.; Tan, X.; Li, J.; Lv, C. Easy synthesis of bimetal PtFe-containing ordered mesoporous carbons and their use as catalysts for selective cinnamaldehyde hydrogenation. New J. Chem. 2013, 37, 1350– 1357,  DOI: 10.1039/c3nj40946e
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    11b
    Easy synthesis of bimetal PtFe-containing ordered mesoporous carbons and their use as catalysts for selective cinnamaldehyde hydrogenation
    Liu, Zhi; Tan, Xiuli; Li, Jia; Lv, Cong
    New Journal of Chemistry (2013), 37 (5), 1350-1357CODEN: NJCHE5; ISSN:1144-0546. (Royal Society of Chemistry)
    This work focuses on the prepn. and characterization of bimetal PtFe-contg. ordered mesoporous carbon (PtFe-OMC) materials with different Pt/Fe ratios and their use as the catalysts in selective cinnamaldehyde hydrogenation. The carbon materials were synthesized by means of an easy one-pot org.-org. self-assembly strategy using H2PtCl6·6H2O and Fe(NO3)3·9H2O as the metal precursors. All the samples were characterized by nitrogen adsorption-desorption, x-ray diffraction, XPS, temp. programmed redn., and TEM, and evaluated for catalytic cinnamaldehyde hydrogenation at various temps. and H2 pressures. The results showed that the Pt-Fe alloy nanoparticles were highly dispersed in the OMC matrix, and the presence of Fe resulted in charge-transfer, and thus, enhanced greatly the selective cinnamaldehyde hydrogenation of the Pt catalyst towards cinnamyl alc.
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    .
    (c) Lee, J.; Kim, Y. T.; Huber, G. W. Aqueous-phase hydrogenation and hydrodeoxygenation of biomass-derived oxygenates with bimetallic catalysts. Green Chem. 2014, 16, 708– 718,  DOI: 10.1039/c3gc41071d
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    11c
    Aqueous-phase hydrogenation and hydrodeoxygenation of biomass-derived oxygenates with bimetallic catalysts
    Lee, Jechan; Kim, Yong Tae; Huber, George W.
    Green Chemistry (2014), 16 (2), 708-718CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
    The reaction rate on a per site basis for aq.-phase hydrogenation (APH) of propanal, xylose, and furfural was measured over various alumina-supported bimetallic catalysts (Pd-Ni, Pd-Co, Pd-Fe, Ru-Ni, Ru-Co, Ru-Fe, Pt-Ni, Pt-Co, and Pt-Fe) using a high-throughput reactor (HTR). The results in this paper demonstrate that the activity of bimetallic catalysts for hydrogenation of a carbonyl group can be 110 times higher than monometallic catalysts. The addn. of Fe to a Pd catalyst increased the activity for hydrogenation of propanal, xylose, and furfural. The Pd1Fe3 catalyst had the highest reaction rate for APH of propanal among all catalysts tested in the HTR. The addn. of Fe to the Pd catalyst increased the reaction rate for xylose hydrogenation by a factor of 51, compared to the monometallic Pd catalyst. However, no bimetallic catalyst tested in this study was more active than the monometallic Ru catalyst for hydrogenation of xylose. The Pd1Fe3 catalyst had the highest reaction rate for APH of furfural, which was 9 times higher than the rate of the Pd catalyst. The Pd1Fe3/Zr-P, a bimetallic bifunctional catalyst, was 14 times more active on a per site basis than a Pd/Zr-P catalyst for aq.-phase hydrodeoxygenation (HDO) of sorbitol in a continuous flow reactor. The addn. of Fe to the Pd catalyst increased the rate of C-C cleavage reactions and promoted the conversion of sorbitan and isosorbide in HDO of sorbitol. Pd1Fe3/Zr-P also had a higher yield of gasoline-range products than the Pd/Zr-P catalyst.
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    .
    (d) Liu, L.; Lou, H.; Chen, M. Selective hydrogenation of furfural over Pt based and Pd based bimetallic catalysts supported on modified multiwalled carbon nanotubes (MWNT). Appl. Catal., A 2018, 550, 1– 10,  DOI: 10.1016/j.apcata.2017.10.003
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    11d
    Selective hydrogenation of furfural over Pt based and Pd based bimetallic catalysts supported on modified multiwalled carbon nanotubes (MWNT)
    Liu, Lujie; Lou, Hui; Chen, Min
    Applied Catalysis, A: General (2018), 550 (), 1-10CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
    Nano-Pt and Nano-Pd particles were introduced to modified multiwalled carbon nanotubes via co-impregnation method for hydrogenation of furfural in liq. phase using ethanol as a solvent. Different transition metal (Cr, Mn, Fe, Co, Ni) was used as promoters using Pt/MWNT and Pd/MWNT catalysts and various supports were also compared to further investigate the hydrogenation process of furfural. Among the catalysts investigated, Pt-Fe/MWNT (Pt: 0.5 wt%) showed highest conversion and selectivity to furfuryl alc. (yield of 87.4%), while Pd-Ni/MWNT (Pd: 0.5 wt%) catalysts exhibited the best catalytic performance (83.3% yield of tetrahydrofurfuryl alc.) under the optimized conditions of 30 bar hydrogen and 5 h, at 100 and 130 °C, resp. Synergistic effect of bimetallic catalysts has been utilized to improve catalytic activity and stability. The extremely active for the selective hydrogenation of furfural over Pt-Fe/MWNT and Pd-Ni/MWNT catalyst might be attributed to active crystal planes exposed over Pt and Pd promoted by Fe and Ni. Catalysts have shown stable activity and selectivity after 5 cycles using Pt-Fe/MWNT and Pd-Ni/MWNT catalysts. Moreover, we suggest that acid sites of conventional supports might have an impact on furfural conversion.
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  12. 12
    (a) Nakamula, I.; Yamanoi, Y.; Imaoka, T.; Yamamoto, K.; Nishihara, H. A Uniform Bimetallic Rhodium/Iron Nanoparticle Catalyst for the Hydrogenation of Olefins and Nitroarenes. Angew. Chem., Int. Ed. 2011, 50, 5830– 5833,  DOI: 10.1002/anie.201102836
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    12a
    A Uniform Bimetallic Rhodium/Iron Nanoparticle Catalyst for the Hydrogenation of Olefins and Nitroarenes
    Nakamula, Ikuse; Yamanoi, Yoshinori; Imaoka, Takane; Yamamoto, Kimihisa; Nishihara, Hiroshi
    Angewandte Chemie, International Edition (2011), 50 (26), 5830-5833, S5830/1-S5830/5CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Relative to the catalytic activity of pure Rh nanoparticles in a dendrimer cage, Rh/Fe bimetallic nanoparticles in dendrimers have improved catalytic activity towards the hydrogenation of olefins, and unlike Wilkinson catalyst could catalyze nitroarene hydrogenation.
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    .
    (b) Kim, J. K.; Lee, J. K.; Kang, K. H.; Lee, J. W.; Song, I. K. Catalytic decomposition of phenethyl phenyl ether to aromatics over Pd–Fe bimetallic catalysts supported on ordered mesoporous carbon. J. Mol. Catal. A: Chem. 2015, 410, 184– 192,  DOI: 10.1016/j.molcata.2015.09.023
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    12b
    Catalytic decomposition of phenethyl phenyl ether to aromatics over Pd-Fe bimetallic catalysts supported on ordered mesoporous carbon
    Kim, Jeong Kwon; Lee, Jong Kwon; Kang, Ki Hyuk; Lee, Jong Won; Song, In Kyu
    Journal of Molecular Catalysis A: Chemical (2015), 410 (), 184-192CODEN: JMCCF2; ISSN:1381-1169. (Elsevier B.V.)
    A series of bimetallic Pd-Fe catalysts supported on ordered mesoporous carbon (denoted as Pd1-FeX/OMC) were prepd. with a variation Fe/Pd molar ratio (X), and they were applied to the catalytic decompn. of phenethyl Ph ether to aroms. Phenethyl Ph ether was used as a lignin model compd. for representing β-O-4 linkage in lignin. The effect of Fe/Pd molar ratio on the catalytic activities and physicochem. properties of bimetallic Pd1-FeX/OMC catalysts was investigated. It was found that cryst. phase, reducibility, chem. state, and electronic property of Pd1-FeX/OMC catalysts were strongly influenced by Fe/Pd molar ratio. In particular, modified electronic property derived from the interaction between Pd and Fe significantly changed the hydrogen adsorption ability and bimetallic structure of the catalysts. Conversion of phenethyl Ph ether continuously decreased with increasing Fe/Pd molar ratio, whereas selectivity for aroms. increased and then became almost const. with increasing Fe/Pd molar ratio. As a consequence, yield for aroms. showed a volcano-shaped trend with respect to Fe/Pd molar ratio. Catalytic performance of Pd1-FeX/OMC catalysts was closely related to the hydrogen adsorption ability and bimetallic structure of the catalysts. Among the catalysts tested, Pd1-Fe0.7/OMC catalyst with moderate hydrogen adsorption ability and with bimetallic structure of Pd1Fe0.7 compn. showed the highest yield for aroms. Thus, an optimal Fe/Pd molar ratio was required to achieve max. prodn. of aroms. through selective cleavage of C-O bond in phenethyl Ph ether over Pd1-FeX/OMC catalysts.
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    .
    (c) Wang, R.; Tang, T.; Huang, K.; Zou, M.; Tao, X.; Yin, H.; Lin, Z.; Dang, Z.; Li, G. Debromination of polybrominated biphenyls (PBBs) by zero valent metals and iron-based bimetallic particles: Mechanisms, pathways and predicting descriptor. Chem. Eng. J. 2018, 351, 773– 781,  DOI: 10.1016/j.cej.2018.06.149
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    12c
    Debromination of polybrominated biphenyls (PBBs) by zero valent metals and iron-based bimetallic particles: Mechanisms, pathways and predicting descriptor
    Wang, Rui; Tang, Ting; Huang, Kaibo; Zou, Mengyao; Tao, Xueqin; Yin, Hua; Lin, Zhang; Dang, Zhi; Lu, Guining
    Chemical Engineering Journal (Amsterdam, Netherlands) (2018), 351 (), 773-781CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
    Polybrominated biphenyls (PBBs) are toxic and persistent brominated flame retardant. Yet their debromination by zero valent metal (ZVM) or iron based bimetals has received far less attention. Here we reported the kinetics and debromination pathways of PBBs in nanoscale zerovalent iron (n-ZVI), microscale zerovalent zinc (m-ZVZ), n-ZVI/Ag and n-ZVI/Pd systems. The results show that the singly occupied MO (SOMO) of PBB anion can be well correlated with the debromination pathways of PBBs by n-ZVI, which verify its ability to predict their debromination pathways through electron transfer (e-transfer) mechanism. We also found that the reaction rates of PBBs in m-ZVZ, n-ZVI/Ag and n-ZVI/Pd systems are much faster than that in n-ZVI system, and the debromination pathways of PBBs in n-ZVI, m-ZVZ and n-ZVI/Ag are exactly the same, suggesting that n-ZVI/Ag debrominate PBBs through an e-transfer mechanism. However, Pd was found to be able to utilize H2 to debrominate PBBs and the debromination pathways of PBBs in Pd-H2 system was the same to those in n-ZVI/Pd system, but was partially different from those in n-ZVI, m-ZVZ and n-ZVI/Ag systems, suggesting that n-ZVI/Pd debrominate PBBs through a H-atom transfer mechanism.
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  13. 13
    (a) Sawama, Y.; Yamada, T.; Yabe, Y.; Morita, K.; Shibata, K.; Shigetsura, M.; Monguchi, Y.; Sajiki, H. Platinum on carbon-catalyzed H-D exchange reaction of aromatic nuclei due to isopropyl alcohol-mediated self-activation of platinum metal in deuterium oxide. Adv. Synth. Catal. 2013, 355, 1529– 1539,  DOI: 10.1002/adsc.201201102
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    13a
    Platinum on Carbon-Catalyzed H-D Exchange Reaction of Aromatic Nuclei due to Isopropyl Alcohol-Mediated Self-Activation of Platinum Metal in Deuterium Oxide
    Sawama, Yoshinari; Yamada, Tsuyoshi; Yabe, Yuki; Morita, Kosuke; Shibata, Kyoshiro; Shigetsura, Masahiro; Monguchi, Yasunari; Sajiki, Hironao
    Advanced Synthesis & Catalysis (2013), 355 (8), 1529-1534CODEN: ASCAF7; ISSN:1615-4150. (Wiley-VCH Verlag GmbH & Co. KGaA)
    An efficient and simple deuteration method of arenes using the platinum on carbon-iso-Pr alc.-cyclohexane-deuterium oxide combination under hydrogen gas-free conditions was accomplished. Since the hydrogen-deuterium exchange reaction cannot be promoted without iso-Pr alc., zerovalent platinum metal (on carbon) is self-activated by the in situ-generated very low amt. of hydrogen or hydrogen-deuterium gas derived from iso-Pr alc. or iso-Pr alc.-d1. Deuterium-labeled compds. with high deuterium contents can be easily isolated by the filtration of platinum on carbon and simple extn. The present hydrogen gas-free method is safe from the viewpoint of process chem. and various arenes possessing a variety of reducible functionalities within the mol. could be effectively and directly deuterium-labeled without undesired redn.
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    .
    (b) Sawama, Y.; Park, K.; Yamada, T.; Sajiki, H. New gateways to the platinum group metal-catalyzed direct deuterium-labeling method utilizing hydroten as a catalyst activator. Chem. Pharm. Bull. 2018, 66, 21– 28,  DOI: 10.1248/cpb.c17-00222
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    13b
    New gateways to the platinum group metal-catalyzed direct deuterium-labeling method utilizing hydrogen as a catalyst activator
    Sawama, Yoshinari; Park, Kwihwan; Yamada, Tsuyoshi; Sajiki, Hironao
    Chemical & Pharmaceutical Bulletin (2018), 66 (1), 21-28CODEN: CPBTAL; ISSN:0009-2363. (Pharmaceutical Society of Japan)
    A review. This review summarized the recent advances in the direct deuteration of sugar, satd. fatty acid and arene derivs. using heterogeneous platinum group metal on carbon catalyst. In this review, the direct activation method of catalysts using in situ-generated hydrogen based on the dehydrogenation of alcs. was introduced.
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    .
    (c) Sawama, Y.; Nakano, A.; Matsuda, T.; Kawajiri, T.; Yamada, T.; Sajiki, H. H-D exchange deuteration of arenes at room temperature. Org. Process Res. Dev. 2019, 23, 648– 653,  DOI: 10.1021/acs.oprd.8b00383
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    13c
    H-D Exchange Deuteration of Arenes at Room Temperature
    Sawama, Yoshinari; Nakano, Akihiro; Matsuda, Takumi; Kawajiri, Takahiro; Yamada, Tsuyoshi; Sajiki, Hironao
    Organic Process Research & Development (2019), 23 (4), 648-653CODEN: OPRDFK; ISSN:1083-6160. (American Chemical Society)
    Arenes underwent C-H deuteration reactions with D2O in the presence of Pt/C, Ir/C, or combinations of both catalysts in isopropanol/D2O under argon at ambient temp. to yield arenes deuterated at the arene C-H bonds.
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    .
    (d) Yamada, T.; Sawama, Y.; Shibata, K.; Morita, K.; Monguchi, Y.; Sajiki, H. Multiple deuteration of alkanes synergistically-catalyzed by platinum and rhodium on carbon as a mixed catalytic system. RSC Adv. 2015, 5, 13727– 13732,  DOI: 10.1039/C4RA16386A
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    13d
    Multiple deuteration of alkanes synergistically-catalyzed by platinum and rhodium on carbon as a mixed catalytic system
    Yamada, Tsuyoshi; Sawama, Yoshinari; Shibata, Kyoshiro; Morita, Kosuke; Monguchi, Yasunari; Sajiki, Hironao
    RSC Advances (2015), 5 (18), 13727-13732CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
    An efficient and mild multiple deuteration method for alkanes catalyzed by the combined use of heterogeneous platinum on carbon (Pt/C) and rhodium on carbon (Rh/C) catalysts in i-PrOD-d8 and D2O as a mixed solvent was developed. The present multi-deuteration was initiated by the transition metal-catalyzed dedeuteration of i-PrOD-d8 to produce D2 and the subsequent C-H bond activation of alkanes catalyzed by the Pt/C and/or Rh/C-D2 complex. This method could be applied to the deuteration of wide variety of linear, branched and cyclic alkanes as useful deuterated materials under mild conditions.
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  14. 14
    Zhang, L.; Zhou, M.; Shao, L.; Wang, W.; Fan, K.; Qin, Q. Reactions of Fe with H2O and FeO with H2. A Combined Matrix Isolation FTIR and Theoretical Study. J. Phys. Chem. A 2001, 105, 6998– 7003,  DOI: 10.1021/jp010914n
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    14
    Reactions of Fe with H2O and FeO with H2. A Combined Matrix Isolation FTIR and Theoretical Study
    Zhang, Luning; Zhou, Mingfei; Shao, Limin; Wang, Wenning; Fan, Kangnian; Qin, Qizong
    Journal of Physical Chemistry A (2001), 105 (29), 6998-7003CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    The study of the reactions of transition metal atoms with water is continued in this work. Here we report the study of the reactions of Fe with H2O and FeO with H2. In agreement with previous thermal atom expts., laser-ablated Fe atoms reacted with H2O to form the FeOH2 and HFeOH mols. as characterized by matrix isolation FTIR spectroscopy. On photolysis, the Fe atoms could further insert into the OH bonds in H2O mols. with a stepwise pattern to form multi metal-oxo core species including HFeOFeH, HFeOFeOH, and possibly HFeOFeOFeH, which were identified by isotopic substitutions and d. functional calcns. Reactions of FeO with H2 also lead to HFeOH as the primary product. In addn., a potential energy surface for the Fe + H2O ↔ FeO + H2 reaction was constructed to elucidate the reaction mechanisms.
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  15. 15
    (a) Peng, B.; Zhao, C.; Mejía-Centeno, I.; Fuentes, G. A.; Jentys, A.; Lercher, J. A. Comparison of kinetics and reaction pathways for hydrodeoxygenation of C3 alcohols on Pt/Al2O3. Catal. Today 2012, 183, 3– 9,  DOI: 10.1016/j.cattod.2011.10.022
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    15a
    Comparison of kinetics and reaction pathways for hydrodeoxygenation of C3 alcohols on Pt/Al2O3
    Peng, Baoxiang; Zhao, Chen; Mejia-Centeno, Isidro; Fuentes, Gustavo A.; Jentys, Andreas; Lercher, Johannes A.
    Catalysis Today (2012), 183 (1), 3-9CODEN: CATTEA; ISSN:0920-5861. (Elsevier B.V.)
    The catalytic hydrodeoxygenation of C3 alcs. (1- and 2-propanol, 1,2- and 1,3-propanediol, and glycerol) on Pt/Al2O3 has been mechanistically explored in the aq. phase. Dehydrogenation on Pt and dehydration on alumina are the main elementary reaction pathways. In water, carbon-carbon bond cleavage for alcs. with terminal hydroxyl groups occurs via decarbonylation of aldehydes (generated by dehydrogenation of alcs.) and decarboxylation of acids, the latter being formed by disproportionation from aldehydes. The presence of water as solvent suppresses the dehydration for mono-alcs. mainly via blocking of Lewis acid sites by water. Dehydration is still the dominating primary reaction for 1,3-propanediol and glycerol, as the higher no. of hydroxyl groups weakens the C-O bond strength. The overall reactivity of C3 alcs. decreases in the order of 1,3-propanediol ≈ glycerol > 1,2-propanediol ≈ 1-propanol.
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    (b) Nakagawa, Y.; Mori, K.; Chen, K.; Amada, Y.; Tamura, M.; Tomishige, K. Hydrogenolysis of CO bond over Re-modified Ir catalyst in alkane solvent. Appl. Catal., A 2013, 468, 418– 425,  DOI: 10.1016/j.apcata.2013.09.021
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    15b
    Hydrogenolysis of CO bond over Re-modified Ir catalyst in alkane solvent
    Nakagawa, Yoshinao; Mori, Kazuma; Chen, Kaiyou; Amada, Yasushi; Tamura, Masazumi; Tomishige, Keiichi
    Applied Catalysis, A: General (2013), 468 (), 418-425CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
    Hydrogenolysis of alcs. was carried out using n-heptane solvent and IrReOx/SiO2 catalyst, which has been known to be active in water solvent. Hydrogenolysis of trans-1,2-cyclohexanediol proceeded more smoothly in n-heptane than in water. The max. yield of cyclohexanol was 74%, and at longer reaction time cyclohexane was selectively formed (>80% yield). Stronger adsorption of substrate on catalyst surface in n-heptane than in water is one of factors in obtaining the good yields. Alkane solvent was also advantageous to water solvent in hydrogenolysis of mono-alcs. The reaction route via acid-catalyzed dehydration and subsequent hydrogenation is enhanced in alkane solvent. On the other hand, the "direct" hydrogenolysis driven by the hydride-like species is suppressed in alkane solvent, leading lower activity in n-heptane for hydrogenolysis of tetrahydrofurfuryl alc. or 1,2-hexanediol, which smoothly react over IrReOx/SiO2 catalyst in water.
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    .
    (c) Zhu, S.; Hao, S.; Zheng, H.; Mo, T.; Li, Y.; Zhu, Y. One-step hydrogenolysis of glycerol to biopropanols over Pt–H4SiW12O40/ZrO2 catalysts. Green Chem. 2012, 14, 2607– 2616,  DOI: 10.1039/c2gc35564g
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    15c
    One-step hydrogenolysis of glycerol to biopropanols over Pt-H4SiW12O40/ZrO2 catalysts
    Zhu, Shanhui; Zhu, Yulei; Hao, Shunli; Zheng, Hongyan; Mo, Tao; Li, Yongwang
    Green Chemistry (2012), 14 (9), 2607-2616CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
    The 1-step hydrogenolysis of biomass-derived glycerol to propanols (1-propanol + isoPrOH), which are known as biopropanols, was studied over different supported Pt-H4SiW12O40 (HSiW) bi-functional catalysts in aq. media. Among the catalysts/supports tested, Pt-HSiW supported over ZrO2 converted glycerol to biopropanols with high selectivity and high yield (94.1%), while exhibiting long-term stability (160 h). This catalyst can be resistant to the impurities present in crude glycerol. The reaction pathway to propanols from glycerol probably proceeds mainly through 1,2-propanediol. With the strategy toward 1-step hydrogenolysis of glycerol to biopropanols sustainably, the biomass can be readily transformed to biodiesel and biopropanols via glycerol, which will bring about the benign development of the biodiesel industry.
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    Arčon, I.; Kolar, J.; Kodre, A.; Hanžel, D.; Strlič, M. XANES analysis of Fe valence in iron gall inks. X-Ray Spectrom. 2007, 36, 199– 205,  DOI: 10.1002/xrs.962
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    XANES analysis of Fe valence in iron gall inks
    Arcon, Iztok; Kolar, Jana; Kodre, Alojz; Hanzel, Darko; Strlic, Matija
    X-Ray Spectrometry (2007), 36 (3), 199-205CODEN: XRSPAX; ISSN:0049-8246. (John Wiley & Sons Ltd.)
    In this study, we investigate the feasibility and reliability of Fe K-edge XANES spectroscopy as a tool in detn. of Fe2+/Fe3+ ratio in historic inks. We have measured Fe K-edge XANES spectra of several historic and model iron gall inks with different Fe2+/Fe3+ ratios, together with some std. ref. Fe2+ and Fe3+ compds. with known local at. structure and symmetry around Fe atoms. We examine different approaches to det. relative amt. of Fe2+ in iron gall inks from the Fe K-edge shifts, and demonstrate that a proper choice of the Fe ref. compds. with similar symmetry, same type of neighbor atoms in nearest coordination shells, arranged in a similar local structure is crucial for the abs. calibration of the Fe K-edge shift and consequently a reliable detn. of Fe2+/Fe3+ ratio in the sample. Best results, with the accuracy of ±2%, are obtained by a linear combination fit with XANES spectrum of FeSO4·7H2O as a ref. for Fe2+ and spectrum of an iron gall ink contg. predominantly Fe3+.
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  17. 17
    Tomita, A.; Shimizu, K.; Kato, K.; Akita, T.; Tai, Y. Mechanism of Low-Temperature CO Oxidation on Pt/Fe-Containing Alumina Catalysts Pretreated with Water. J. Phys. Chem. C 2013, 117, 1268– 1277,  DOI: 10.1021/jp304940f
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    17
    Mechanism of Low-Temperature CO Oxidation on Pt/Fe-Containing Alumina Catalysts Pretreated with Water
    Tomita, Atsuko; Shimizu, Ken-ichi; Kato, Kazuo; Akita, Tomoki; Tai, Yutaka
    Journal of Physical Chemistry C (2013), 117 (3), 1268-1277CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    In a previous article (Catal. Commun. 2012, , 194), we reported that Pt/Fe-contg. alumina catalysts pretreated with water could catalyze CO oxidn. even below room temp. To clarify the effect of the water pretreatment and the reaction mechanism of the novel catalytic system, in situ Fourier transform IR (FT-IR), and X-ray absorption fine structure (XAFS) measurements during CO oxidn. were conducted. From FT-IR measurements, it was revealed that the Pt surface of the catalyst was covered with CO and that the adsorbed CO mols. did not desorb easily, as in the case of conventional Pt/Al2O3 catalyst. Pt LIII XAFS results also suggested the presence of CO on the Pt surface during CO oxidn. Thresholds of Fe K X-ray absorption near-edge structure shifted with the change between oxidative (0.5% O2/He) and reductive (1% CO/He) atmospheres, indicating that the Fe redox change Fe2+ ↔ Fe3+ can participate in the reaction. From the degree of the shifts and av. Pt diams. derived from high-angle annular dark-field scanning transmission electron microscopy and metal dispersion measurements, it was concluded that PtNP/FeOx boundaries were efficiently formed upon the water pretreatment. The enhanced reactivity of the water-pretreated catalyst can be attributed to the increased no. of boundaries and Pt diam.
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  18. 18

    X-ray photoelectron spectroscopy (XPS) analysis of fresh 10% Pt/C indicated that zero valent of platinum was supported on carbon. See Supporting Information.

    There is no corresponding record for this reference.
  19. 19

    Although Pt/C-catalyzed dehydrogenation of 9 in the absence of 8 provided 8 as a dehydrogenated product, methylcyclohexane was also produced by the hydrogenation of 9 using H2 in situ-generated via the dehydrogenation process of 8 to 9. See Supporting Information.

    There is no corresponding record for this reference.
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    (a) Birch, A. J. Reduction by Dissolving Metals. J. Chem. Soc. 1944, 430– 436,  DOI: 10.1039/jr9440000430
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    Reduction by dissolving metals. I
    Birch, Arthur J.
    Journal of the Chemical Society (1944), (), 430-6CODEN: JCSOA9; ISSN:0368-1769.
    Since Na in liq. NH3 behaves as a soln. of metal cations and solvated electrons in equil. with metal atoms, it might be expected to reduce by "electron addn." but the addn. of a ready proton source (such as an alc.) to the reagent renders redn. by nascent H a possibility. The action of Na in liq. NH3 on a no. of C10H8 and C6H6 derivs. in the presence and in the absence of an alc. has been studied to det. whether the presence of the latter alters the course of the reaction. 1-C10H7OH (I) (5.5 g.) and 1.5 g. of NaNH2 in 60 cc. liq. NH3, treated with 1.8 g. Na during 1 h., give 0.3 g. of the 5,8-dihydro deriv. (II); without NaNH2 but with 2.9 g. tert-AmOH, the yield of II was 3.2 g. (65%); 10 g. I and 2.7 g. NaNH2 in 110 cc. NH3, treated with 12.5 g. tert-AmOH and 3.2 g. Na, give about 9 g. of II. Under the 3 above conditions, 2-C10H7OH gives (1) a trace of the 5,8-dihydro deriv. and β-tetralone, (2) 65% and (3) 50% of the tetralone. Treatment of the alk. soln. from (1) with Me2SO4 gives mainly ar-dihydro-2-methoxynaphthalene, b14 145-50°. 1-C10H7CO2H with NaNH2 and Na in NH3 gives the 1,4-dihydro deriv., m. 75°; heating with 20% NaOH at 100° for 30 min. gives the 3,4-dihydro deriv., m. 112°. MeO derivs. of C6H6 and its homologs give about 10% of the phenol (through demethylation) and a mixt. of the starting material and redn. product which were difficult to sep.; the presence of the dihydro deriv. was proved by treatment with hot dil. mineral acid, the product being α,β-unsatd. ketones. PhOMe gave 20% of 2-cyclohexen-1-one (III). 2-MeC6H4OMe gave 12% of the 6-Me deriv. of III (2,4-dinitrophenylhydrazone, bright orange, m. 122-6°). 3-MeC6H4OMe (20 g.) in 28 g. MeOH, added during 1 h. to 20 g. Na in 500 cc. liq. NH3, gave 2 fractions: one b. 105-20° (contg. 1-methyl-cyclohexene, identified as the nitrosochloride, m. 92-3°); the other b. 165-73° and contained essentially 3-methyl-2,5-dihydroanisole (IV); it showed no light absorption in the region 2400-2800 A. IV, refluxed with 10% aq. H2SO4 for 1 h. and treated with H2NNHCONH2, gives 3-methyl-2-cyclohexen-1-one semicarbazidosemicarbazone, m. 210° (decompn.), insol. in boiling EtOH, and the semicarbazone, m. 199-200°; 2,4-dinitrophenylhydrazone, dark red, m. 173°. 4-MeOC6H4Me gives 33% of the 4-Me deriv. of III. 2,6-Me2C6H3OMe gives 10% of the 2,6-di-Me deriv. of III; semicarbazone, cream, m. 210-11°; 2,4-dinitrophenylhydrazone, red, m. 153°. 2,5-Me2C6H3OMe gives 15% of the 3,6(?)-di-Me deriv. of III, whose semicarbazidosemicarbazone, m. 214° (decompn.) (no semicarbazone is formed); 2,4-dinitrophenylhydrazone, orange-red, m. 134°. 2,4-Me2C6H3OMe gives 22% of the 4,6-di-Me deriv. of III; semicarbazone, cream, m. 175°; 2,4-dinitrophenylhydrazone, red, m. 152°. 3,4-Me2C6H3OMe gives 35% of the 3,4(?)-di-Me deriv. of III; semicarbazone, cream, m. 193°; 2,4-dinitrophenylhydrazone, red, m. 146°. 3,5-Me2C6H3OMe gives 16% of the 3,5-di-Me deriv. of III; semicarbazidosemicarbazone(?), m. 199° (decompn.). 5-Methoxy-1,2,3,4-tetrahydronaphthalene gave a trace of 1-keto-Δ9,10-octalin but the 6-MeO isomer (V) yields 44% of 2-keto-Δ1,9-octalin; the 5-Me deriv. of V did not give a ketonic product. 5-Methoxyhydrindene gives 30% of 5-keto-4,9-tetrahydrohydrindene; semicarbazone, cream, m. 228-30°; 2,4-dinitrophenylhydrazone, red, m. 197-8°. 5-Methyl-2-isopropylanisole gives a small yield of piperitone. Geranyl Me ether gives geraniolene, b. 165-70°. m-C6H4Me2 (18 g.) and 25 cc. EtOH, added to 10 g. Na in 150 cc. liq. NH3, give 15 g. of an oil b. 142-4° which contains about 21% of benzenoid material (UV spectrum); it yields a nitrosochloride, m. 123° (decompn.), and a nitrolpiperidine, m. 137°, of 2,5-dihydro-m-xylene. The structure was established by ozonolysis, CH2Ac2 being formed. p-C6H4Me2 gives 2,5-(?)-dihydro-p-xylene; this gives a nitrosochloride m. 98° and a nitrolpiperidine, m. 133°. p-Cymene gives a fraction b. 179-80° which contains about 25-30% of a dihydro deriv., consisting partly of γ-terpinene. Tetralin gives an oil, b. 204-8° which contains some 1,2,3,4,5,8-hexahydronaphthalene, whose nitrosochloride, bright blue, m. 91°. If a C6H6 ring bearing MeO and alkyl groups (or the ends of a satd. ring) is written in the Dewar formulas in which the bridge head is not occupied by a MeO group, the chief redn. product will correspond to the formula having the least no. of substituents at the bridge head. 2,3-Disubstituted anisoles give 2 possible formulas between which the rules do not distinguish and the rule is restated as follows: Redn. will tend to be initiated (a) in an unoccupied position and (b) o- or m-rather than p- to an alkyl or MeO group, the latter having the greater deactivating effect in both cases. The mechanism of the nascent H redn. is still in doubt. The practical application of this type of redn. is limited by the low soly. of many compds. in liq. NH3, since redn. is in competition with H evolution.
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    A Mechanistic Analysis of the Birch Reduction
    Zimmerman, Howard E.
    Accounts of Chemical Research (2012), 45 (2), 164-170CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
    The Birch Redn. is one of the main reactions of org. chem. The reaction involves the reaction of dissolving metals in ammonia with arom. compds. to produce 1,4-cyclohexadienes. Discovered by Arthur Birch in 1944, the reaction occupies 300 pages in Org. Reactions to describe its synthetic versatility. Thus, it is remarkable that the reaction mechanism has been so very controversial and only relatively recently has been firmly established. Perhaps this is not that surprising, since the reaction also has many unusual and esoteric mechanistic facets. Here, I provide a description of how I have applied ever-evolving levels of quantum mechanics and a novel exptl. test to understand details of the mechanism and the origins of the selectivities obsd. in the Birch redn. The reaction involves an initial radical anion resulting from introduction of an electron from the blue liq. ammonia soln. of free electrons formed by the dissoln. of Li or related metals. This radical anion is protonated by an alc. and then further reduced to a carbanion. Finally, the carbanion is protonated using a second proton to afford a nonconjugated cyclohexadiene. The regiochem. depends on substituents present. With 18 resonance structures in the case of anisole radical anion, prediction of the initial protonation site would seem difficult. Nevertheless, computational methods from Huckel theory through modern d. functional calcns. do correctly predict the site of protonation. An esoteric test established this mechanism exptl. The nature of the carbanion also is of mechanistic interest, and the preponderance of the resonance structure shown was revealed from Huckel calcns. involving variable bond orders. For the trianion from benzoic acid, parallel questions about structure are apparent, and have been answered. Some mechanistic questions are answered exptl. and some by modern computations. Recently, our mechanistic understanding has led to a variety of synthetic applications. For example, the prepn. of alkyl aroms. from benzoic acids makes use of the intermediates formed in these reactions. This Account provides an overview of both exptl. techniques and theor. methodol. used to provide detailed mechanistic understanding of the Birch Redn.
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    Iron-catalysed, hydride-mediated reductive cross-coupling of vinyl halides and Grignard reagents
    Le Bailly, Bryden A. F.; Greenhalgh, Mark D.; Thomas, Stephen P.
    Chemical Communications (Cambridge, United Kingdom) (2012), 48 (10), 1580-1582CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    An iron-catalyzed, hydride-mediated reductive cross-coupling reaction has been developed for the prepn. of alkanes. Using a bench-stable iron(II) pre-catalyst, reductive cross-coupling of vinyl iodides, bromides and chlorides with aryl- and alkyl Grignard reagents successfully gave the products of formal sp3-sp3 cross-coupling reactions.
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    Cai, Y.; Qian, X.; Gosmini, C. Cobalt-Catalyzed Csp3-Csp3 Homocoupling. Adv. Synth. Catal. 2016, 358, 2427– 2430,  DOI: 10.1002/adsc.201600213
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    Cobalt-Catalyzed Csp3-Csp3 Homocoupling
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    Advanced Synthesis & Catalysis (2016), 358 (15), 2427-2430CODEN: ASCAF7; ISSN:1615-4150. (Wiley-VCH Verlag GmbH & Co. KGaA)
    An efficient and easy method for Csp3-Csp3 homocoupling was developed using cobalt bromide as catalyst. A series of functionalized alkyl bromides and alkyl chlorides were coupled in high yields under mild conditions. This reaction seems to involve a radical intermediate.
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  • Abstract

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    Scheme 1

    Scheme 1. Pt/C–Fe-Catalyzed Arene Reduction in 2-Propanol as a Solvent and Hydrogen Source
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    Scheme 2

    Scheme 2. Substrate Scope of the Reduction Reaction
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    a10% Pt/C (10 mol %) and Fe0 (10 mol %) were used.

    Scheme 3

    Scheme 3. Reduction of 7-Tetradecene under Different Conditions
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    Scheme 4

    Scheme 4. Comparison of Pt/C–Fe, Pt/C, and Fe Hydrogenation Activities
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    Figure 1

    Figure 1. Time profile of the internal pressure inside a 50 mL sealed glass tube filled with different reaction mixtures.

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    Figure 2

    Figure 2. X-ray fluorescence profiles of the mixtures A and B (see Scheme 1).

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    Figure 3

    Figure 3. (a) Normalized Fe K-edge XANES profiles. (b) Plot of Fe K-edge absorption edge energy shift vs the valence of Fe. Reaction conditions A and B are described in Scheme 1.

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    Figure 4

    Figure 4. (a) Normalized Pt LIII-edge XANES profiles. (b) Plot of Pt LIII-edge absorption edge energy shift vs the valence of Pt. Reaction conditions A and B are described in Scheme 1.

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    Scheme 5

    Scheme 5. Proposed Mechanisms or Pt/C–Fe-Catalyzed Arene Reduction
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    Scheme 6

    Scheme 6. Pt-Catalyzed Dehydrogenative Regeneration of Toluene (8) from Cyclohexadiene Derivative 9
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    Scheme 7

    Scheme 7. Results of 1,2-Diphenylethane (4) Reduction under the Conditions of Pt/C Catalysis
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    Scheme 8

    Scheme 8. Reaction Using Deuterated Solventsa
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    aItalic number means the deuterium content

  • References

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    This article references 22 other publications.

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      A review. Hydrogen storage for stationary and mobile applications is an expanding research topic. One of the more promising hydrogen storage techniques relies on the reversibility and high selectivity of liq. org. hydrides, in particular, methylcyclohexane (MCH). The use of liq. org. hydrides in hydrogen storage also provides high gravimetric and volumetric hydrogen d., low potential risk, and low capital investment because it is largely compatible with the current transport infrastructure. Despite its tech., economical, and environmental advantages, the concept of hydrogen storage in liq. org. carriers has not been com. established because of tech. limitations related to the amt. of energy required to ext. the hydrogen from liq. org. hydride and the insufficient stability of the dehydrogenation catalyst. This paper provides a review for the effort that has been directed toward the development of this concept over the past few decades and mainly focuses on the catalytic prodn. of hydrogen from MCH. The topics that have been covered are the kinetics of MCH dehydrogenation over Pt/Al2O3 and Pt-Re/Al2O3 catalysts, the kinetics of catalyst deactivation, the thermodn. equil. in MCH dehydrogenation, and the sulfur impact on the MCH dehydrogenation reaction.
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      Future energy systems will be detd. by the increasing relevance of solar and wind energy. Crude oil and gas prices are expected to increase in the long run, and penalties for CO2 emissions will become a relevant economic factor. Solar- and wind-powered electricity will become significantly cheaper, such that hydrogen produced from electrolysis will be competitively priced against hydrogen manufd. from natural gas. However, to handle the unsteadiness of system input from fluctuating energy sources, energy storage technologies that cover the full scale of power (in megawatts) and energy storage amts. (in megawatt hours) are required. Hydrogen, in particular, is a promising secondary energy vector for storing, transporting, and distributing large and very large amts. of energy at the gigawatt-hour and terawatt-hour scales. However, we also discuss energy storage at the 120-200-kWh scale, for example, for onboard hydrogen storage in fuel cell vehicles using compressed hydrogen storage. This article focuses on the characteristics and development potential of hydrogen storage technologies in light of such a changing energy system and its related challenges. Technol. factors that influence the dynamics, flexibility, and operating costs of unsteady operation are therefore highlighted in particular. Moreover, the potential for using renewable hydrogen in the mobility sector, industrial prodn., and the heat market is discussed, as this potential may det. to a significant extent the future economic value of hydrogen storage technol. as it applies to other industries. This evaluation elucidates known and well-established options for hydrogen storage and may guide the development and direction of newer, less developed technologies.
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    3. 3

      Arene reduction using H2; Recent selected papers:

      (a) Wiesenfeldt, M. P.; Nairoukh, Z.; Daloton, T.; Glorius, F. Selective Arene Hydrogenation Provides Direct Access to Saturated Carbo- and Heterocycles. Angew. Chem., Int. Ed. 2019,  DOI: 10.1002/anie.201814471
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      .
      (b) Tran, B. L.; Fulton, J. L.; Linehan, J. C.; Lercher, J. A.; Bullock, R. M. Rh (CAAC)-Catalyzed Arene Hydrogenation: Evidence for Nanocatalysis and Sterically Controlled Site-Selective Hydrogenation. ACS Catal. 2018, 8, 8441– 8449,  DOI: 10.1021/acscatal.8b02589
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      3b
      Rh(CAAC)-Catalyzed Arene Hydrogenation: Evidence for Nanocatalysis and Sterically Controlled Site-Selective Hydrogenation
      Tran, Ba L.; Fulton, John L.; Linehan, John C.; Lercher, Johannes A.; Bullock, R. Morris
      ACS Catalysis (2018), 8 (9), 8441-8449CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      We report the arene hydrogenation of ethers, amides, and esters at room temp. and low hydrogen pressure, starting from [(CAAC)Rh(COD)Cl] (CAAC = cyclic alkyl amino carbene). Kinetic, mechanistic, and Rh K-edge XAFS studies showed formation of Rh nanoparticles from [(CAAC)Rh(COD)Cl], in contrast to a previous report of [(CAAC)Rh(COD)Cl] functioning as a homogeneous catalyst for arene hydrogenation. We detd. that the site-selective arene hydrogenation catalyzed by this system is under steric control, as shown by detailed competition expts. with derivs. of ethers, amides, and esters bearing different arom. rings of varying electronic and steric influence. This work illustrates the potential of CAAC ligands in the formation and stabilization of a colloidal dispersion of stable nanoparticle catalysts.
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      (c) Ohtaka, A.; Kawase, M.; Aihara, S.; Miyamoto, Y.; Terada, A.; Nakamura, K.; Hamasaka, G.; Uozumi, Y.; Shinagawa, T.; Shimomura, O.; Nomura, R. Poly(tetrafluoroethylene)-Stabilized Metal Nanoparticles: Preparation and Evaluation of Catalytic Activity for Suzuki, Heck, and Arene Hydrogenation in Water. ACS Omega 2018, 3, 10066– 10073,  DOI: 10.1021/acsomega.8b01338
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      3c
      Poly(tetrafluoroethylene)-Stabilized Metal Nanoparticles: Preparation and Evaluation of Catalytic Activity for Suzuki, Heck, and Arene Hydrogenation in Water
      Ohtaka, Atsushi; Kawase, Misa; Aihara, Shunichiro; Miyamoto, Yasuhiro; Terada, Ayaka; Nakamura, Kenta; Hamasaka, Go; Uozumi, Yasuhiro; Shinagawa, Tsutomu; Shimomura, Osamu; Nomura, Ryoki
      ACS Omega (2018), 3 (8), 10066-10073CODEN: ACSODF; ISSN:2470-1343. (American Chemical Society)
      Poly(tetrafluoroethylene)-stabilized Pd nanoparticles (PTFE-PdNPs) were prepd. in water with (4-methylphenyl)boronic acid as a reductant and characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), XPS, and inductively coupled plasma-at. emission spectroscopy (ICP-AES). Small Pd nanoparticles with a fairly uniform size were obtained in the presence of PTFE, whereas aggregation of palladium was obsd. in the absence of PTFE. PTFE-PdNPs showed high catalytic activity for the Suzuki coupling reaction in water and were reused without any loss of activity. No palladium species were obsd. by ICP-AES anal. in the reaction soln. after the reaction, nor was any change in particle size obsd. after the recycle expt. PTFE-PdNPs also exhibited excellent catalytic activity and reusability for the Heck reaction in water. Although palladium species were not detected in the reaction soln. after the reaction, aggregates and smaller sizes of Pd nanoparticles were obsd. in the TEM image of the recovered catalyst. PTFE was also useful as the stabilizer of RhNPs prepd. by redn. with NaBH4. PTFE-RhNPs showed high catalytic activity and reusability toward arene hydrogenation under mild conditions.
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      (d) Miyamura, H.; Suzuki, A.; Yasukawa, T.; Kobayashi, S. Polysilane-Immobilized Rh–Pt Bimetallic Nanoparticles as Powerful Arene Hydrogenation Catalysts: Synthesis, Reactions under Batch and Flow Conditions and Reaction Mechanism. J. Am. Chem. Soc. 2018, 140, 11325– 11334,  DOI: 10.1021/jacs.8b06015
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      3d
      Polysilane-Immobilized Rh-Pt Bimetallic Nanoparticles as Powerful Arene Hydrogenation Catalysts: Synthesis, Reactions under Batch and Flow Conditions and Reaction Mechanism
      Miyamura, Hiroyuki; Suzuki, Aya; Yasukawa, Tomohiro; Kobayashi, Shu
      Journal of the American Chemical Society (2018), 140 (36), 11325-11334CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Hydrogenation of arenes is an important reaction not only for hydrogen storage and transport but also for the synthesis of functional mols. such as pharmaceuticals and biol. active compds. Here, we describe the development of heterogeneous Rh-Pt bimetallic nanoparticle catalysts for the hydrogenation of arenes with inexpensive polysilane as support. The catalysts could be used in both batch and continuous-flow systems with high performance under mild conditions and showed wide substrate generality. In the continuous-flow system, the product could be obtained by simply passing the substrate and 1 atm H2 through a column packed with the catalyst. Remarkably, much higher catalytic performance was obsd. in the flow system than in the batch system, and extremely strong durability under continuous-flow conditions was demonstrated (>50 days continuous run; turnover no. >3.4 × 105). Furthermore, details of the reaction mechanisms and the origin of different kinetics in batch and flow were studied, and the obtained knowledge was applied to develop completely selective arene hydrogenation of compds. contg. two arom. rings toward the synthesis of an active pharmaceutical ingredient.
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      (e) Joannou, M. V.; Bezdek, M. J.; Chirik, P. J. Pyridine(diimine) Molybdenum-Catalyzed Hydrogenation of Arenes and Hindered Olefins: Insights into Precatalyst Activation and Deactivation Pathways. ACS Catal. 2018, 8, 5276– 5285,  DOI: 10.1021/acscatal.8b00924
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      3e
      Pyridine(diimine) Molybdenum-Catalyzed Hydrogenation of Arenes and Hindered Olefins: Insights into Precatalyst Activation and Deactivation Pathways
      Joannou, Matthew V.; Bezdek, Mate J.; Chirik, Paul J.
      ACS Catalysis (2018), 8 (6), 5276-5285CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      Pyridine(diimine) molybdenum bis(olefin) and bis(alkyl) complexes were synthesized, characterized, and examd. for their catalytic activity in the hydrogenation of benzene and a selection of substituted arenes. The molybdenum bis(alkyl) complex (4-tBu-iPrPDI)Mo(CH2SiMe3)2 (iPrPDI = 2,6-(2,6-(C(CH3)2H)2C6H3N=CMe)2C5H3N) exhibited the highest activity for the hydrogenation of benzene, producing cyclohexane in >98% yield at 23 °C under 4 atm of hydrogen after 48 h. Toluene and o-xylene were similarly hydrogenated to their resp. cycloalkanes, with the latter yielding predominantly (79:21 dr) cis-1,2-dimethylcyclohexane. The molybdenum-catalyzed hydrogenation of naphthalene yielded tetralin exclusively, and this selectivity was maintained at higher H2 pressure. At 32 atm of H2, more hindered arenes such as monosubstituted benzenes, biphenyl, and m- and p-xylenes underwent hydrogenation with yields ranging between 20 and >98%. (4-tBu-iPrPDI)Mo(CH2SiMe3)2 was also a competent alkene hydrogenation catalyst, supporting stepwise redn. of benzene to cyclohexadiene and cyclohexene during molybdenum-catalyzed arene hydrogenation. Deuterium labeling studies for the molybdenum-catalyzed hydrogenation of benzene produced numerous isotopologues and stereoisomers of cyclohexane, indicating reversible hydride (deuteride) insertion/β-H(D) elimination, diene/olefin binding, and allylic C-H(D) activation during the reaction. The resting state of the catalyst under neat conditions was established as the η6-benzene complex (iPrPDI)Mo(η6-benzene). Under catalytic conditions, pyridine underwent C-H activation of the 2-position and furan underwent formal C-O oxidative addn. to yield a "metallapyran". Both reactions were identified as important catalyst deactivation pathways for the attempted molybdenum-catalyzed hydrogenation of heteroarenes.
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      (f) Ghosh, S.; Jagirdar, B. R. Effect of the Crystallographic Phase of Ruthenium Nanosponges on Arene and Substituted-Arene Hydrogenation Activity. ChemCatChem 2018, 10, 3086– 3095,  DOI: 10.1002/cctc.201800287
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      3f
      Effect of the Crystallographic Phase of Ruthenium Nanosponges on Arene and Substituted-Arene Hydrogenation Activity
      Ghosh, Sourav; Jagirdar, Balaji R.
      ChemCatChem (2018), 10 (14), 3086-3095CODEN: CHEMK3; ISSN:1867-3880. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Identifying crystal structure sensitivity of a catalyst for a particular reaction is an important issue in heterogeneous catalysis. In this context, the activity of different phases of ruthenium catalysts for benzene hydrogenation has not yet been studied. The synthesis of hcp. and fcc. phases of ruthenium nanosponges by chem. redn. method was described. Redn. of ruthenium chloride using ammonia borane (AB) and tert-butylamine borane (TBAB) as reducing agents gave ruthenium nanosponge in its hcp. phase. However, redn. using sodium borohydride (SB) afforded ruthenium nanosponge in its fcc. phase. The as prepd. hcp. ruthenium nanosponge is catalytically more active compared to the as prepd. fcc. ruthenium nanosponge for hydrogenation of benzene. The hcp. ruthenium nanosponge is thermally stable and recyclable over several cycles. This self-supported hcp. ruthenium nanosponge shows excellent catalytic activity towards hydrogenation of various substituted benzenes. Moreover, the ruthenium nanosponge catalyst was found to bring about selective hydrogenation of arom. cores of phenols and aryl ethers to the resp. alicyclic products without hydrogenolysis of the C-O bond.
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      (g) Ji, P.; Song, Y.; Drake, T.; Veroneau, S. S.; Lin, Z.; Pan, X.; Lin, W. Titanium(III)-Oxo Clusters in a Metal–Organic Framework Support Single-Site Co(II)-Hydride Catalysts for Arene Hydrogenation. J. Am. Chem. Soc. 2018, 140, 433– 440,  DOI: 10.1021/jacs.7b11241
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      3g
      Titanium(III)-Oxo Clusters in a Metal-Organic Framework Support Single-Site Co(II)-Hydride Catalysts for Arene Hydrogenation
      Ji, Pengfei; Song, Yang; Drake, Tasha; Veroneau, Samuel S.; Lin, Zekai; Pan, Xiandao; Lin, Wenbin
      Journal of the American Chemical Society (2018), 140 (1), 433-440CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Titania (TiO2) is widely used in the chem. industry as an efficacious catalyst support, benefiting from its unique strong metal-support interaction. Many proposals have been made to rationalize this effect at the macroscopic level, yet the underlying mol. mechanism is not understood due to the presence of multiple catalytic species on the TiO2 surface. This challenge can be addressed with metal-org. frameworks (MOFs) featuring well-defined metal oxo/hydroxo clusters for supporting single-site catalysts. Herein we report that the Ti8(μ2-O)8(μ2-OH)4 node of the Ti-BDC MOF (MIL-125) provides a single-site model of the classical TiO2 support to enable CoII-hydride-catalyzed arene hydrogenation. The catalytic activity of the supported CoII-hydride is strongly dependent on the redn. of the Ti-oxo cluster, definitively proving the pivotal role of TiIII in the performance of the supported catalyst. This work thus provides a molecularly precise model of Ti-oxo clusters for understanding the strong metal-support interaction of TiO2-supported heterogeneous catalysts.
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      (h) Tang, N.; Cong, Y.; Shang, Q.; Wu, C.; Xu, G.; Wang, X. Coordinatively Unsaturated Al3+ Sites Anchored Subnanometric Ruthenium Catalyst for Hydrogenation of Aromatics. ACS Catal. 2017, 7, 5987– 5991,  DOI: 10.1021/acscatal.7b01816
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      3h
      Coordinatively Unsaturated Al3+ Sites Anchored Subnanometric Ruthenium Catalyst for Hydrogenation of Aromatics
      Tang, Nanfang; Cong, Yu; Shang, Qinghao; Wu, Chuntian; Xu, Guoliang; Wang, Xiaodong
      ACS Catalysis (2017), 7 (9), 5987-5991CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      Single metal atoms and metal clusters have attracted much attention because of their high dispersity, special electronic structures, and uniformity of active sites as heterogeneous catalysts, but it is still challenging to generate stable single atoms and clusters with high metal loadings. Supports play a crucial role in detg. particle morphol. and maintaining dispersion. Herein we synthesize an amorphous alumina with 29% coordinatively unsatd. pentacoordinate Al3+ (Al3+penta) sites, which can anchor atomically dispersed Ru species with 1 wt. % loading. Strong interactions between Ru and Al3+penta centers were detected, resulting in distinct Ru geometric and electronic features. When used in benzene hydrogenation reaction, fairly high specific activity (TOF = 5180 h-1) were obtained. The high catalytic performance is considered closely correlated with the high utilization of special Ru active sites.
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      (i) Cui, X.; Surkus, A.-E.; Junge, K.; Topf, C.; Radnik, J.; Kreyenschulte, C.; Beller, M. Highly selective hydrogenation of arenes using nanostructured ruthenium catalysts modified with a carbon–nitrogen matrix. Nat. Commun. 2016, 7, 11326  DOI: 10.1038/ncomms11326
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      3i
      Highly selective hydrogenation of arenes using nanostructured ruthenium catalysts modified with a carbon-nitrogen matrix
      Cui, Xinjiang; Surkus, Annette-Enrica; Junge, Kathrin; Topf, Christoph; Radnik, Joerg; Kreyenschulte, Carsten; Beller, Matthias
      Nature Communications (2016), 7 (), 11326pp.CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
      Selective hydrogenations of (hetero)arenes represent essential processes in the chem. industry, esp. for the prodn. of polymer intermediates and a multitude of fine chems. Herein, a new type of well-dispersed Ru nanoparticles supported on a nitrogen-doped carbon material obtained from ruthenium chloride and dicyanamide in a facile and scalable method was described. These novel catalysts were stable and display both excellent activity and selectivity in the hydrogenation of arom. ethers, phenols as well as other functionalized substrates to the corresponding alicyclic reaction products. Furthermore, redn. of the arom. core was preferred over hydrogenolysis of the C-O bond in the case of ether substrates. The selective hydrogenation of biomass-derived arenes, such as lignin building blocks, played a pivotal role in the exploitation of novel sustainable feedstocks for chem. prodn. and represents a notoriously difficult transformation up to now.
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      (j) Karakhanov, E. A.; Maximov, A. L.; Zolotukhina, A. V.; Terenina, M. V.; Vutolkina, A. V. Nanoheterogeneous ruthenium-containing catalysts based on dendrimers in the hydrogenation of aromatic compounds under two-phase conditions. Pet. Chem. 2016, 56, 491– 502,  DOI: 10.1134/S0965544116060037
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      3j
      Nanoheterogeneous ruthenium-containing catalysts based on dendrimers in the hydrogenation of aromatic compounds under two-phase conditions
      Karakhanov, E. A.; Maximov, A. L.; Zolotukhina, A. V.; Terenina, M. V.; Vutolkina, A. V.
      Petroleum Chemistry (2016), 56 (6), 491-502CODEN: PHEME4; ISSN:0965-5441. (Pleiades Publishing, Ltd.)
      Nanoheterogeneous catalysts based on ruthenium nanoparticles dispersed in crosslinked dendrimer matrixes with a size of polymer particles of 100-500 nm show high activity in the hydrogenation of arom. compds. under two-phase conditions. The addn. of water to the reaction medium exerts a strong promoting effect on the activity of the catalysts: The turnover frequency increases by a factor of 3-90 depending on the substrate. When bimetallic (PdRu) nanoparticles are incorporated into the catalyst compn., the rate of benzene hydrogenation increases while the rate of transformation of substituted benzenes decreases.
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      (k) Ibrahim, M.; Poreddy, R.; Philippot, K.; Riisager, A.; Garcia-Suarez, E. J. Chemoselective hydrogenation of arenes by PVP supported Rh nanoparticles. Dalton Trans. 2016, 45, 19368– 19373,  DOI: 10.1039/C6DT03668F
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      3k
      Chemoselective hydrogenation of arenes by PVP supported Rh nanoparticles
      Ibrahim, Mahmoud; Poreddy, Raju; Philippot, Karine; Riisager, Anders; Garcia-Suarez, Eduardo J.
      Dalton Transactions (2016), 45 (48), 19368-19373CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
      Polyvinylpyrrolidone-stabilized Rh nanoparticles (RhNPs/PVP) of ca. 2.2 nm in size were prepd. by the hydrogenation of the organometallic complex [Rh(η3-C3H5)3] in the presence of PVP and evaluated as a catalyst in the hydrogenation of a series of arene substrates as well as levulinic acid and Me levulinate. The catalyst showed excellent activity and selectivity towards arom. ring hydrogenation compared to other reported transition metal-based catalysts under mild reaction conditions (room temp. and 1 bar H2). Furthermore, it was shown to be a highly promising catalyst for the hydrogenation of levulinic acid and Me levulinate in water leading to quant. formation of the fuel additive γ-valerolactone under moderate reaction conditions compared to previously reported catalytic systems.
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      (l) Morioka, Y.; Matsuoka, A.; Binder, K.; Knappett, B. R.; Wheatley, A. E. H.; Naka, H. Selective hydrogenation of arenes to cyclohexanes in water catalyzed by chitin-supported ruthenium nanoparticles. Catal. Sci. Technol. 2016, 6, 5801– 5805,  DOI: 10.1039/C6CY00899B
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      3l
      Selective hydrogenation of arenes to cyclohexanes in water catalyzed by chitin-supported ruthenium nanoparticles
      Morioka, Yuna; Matsuoka, Aki; Binder, Kellie; Knappett, Benjamin R.; Wheatley, Andrew E. H.; Naka, Hiroshi
      Catalysis Science & Technology (2016), 6 (15), 5801-5805CODEN: CSTAGD; ISSN:2044-4753. (Royal Society of Chemistry)
      The selective hydrogenation of arom. compds. to cyclohexanes was found to be promoted by chitin-supported ruthenium nanoparticles (Ru/chitin) under near-neutral, aq. conditions without the loss of C-O/C-N linkages at benzylic positions.
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      (m) Pélisson, C.-H.; Denicourt-Nowicki, A.; Roucoux, A. Magnetically Retrievable Rh(0) Nanocomposite as Relevant Catalyst for Mild Hydrogenation of Functionalized Arenes in Water. ACS Sustainable Chem. Eng. 2016, 4, 1834– 1839,  DOI: 10.1021/acssuschemeng.6b00045
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      3m
      Magnetically Retrievable Rh(0) Nanocomposite as Relevant Catalyst for Mild Hydrogenation of Functionalized Arenes in Water
      Pelisson, Carl-Hugo; Denicourt-Nowicki, Audrey; Roucoux, Alain
      ACS Sustainable Chemistry & Engineering (2016), 4 (3), 1834-1839CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
      A Rh0@γ-Fe2O3 nanocomposite was easily prepd. by straightforward deposit of metal nanoparticles on the nonfunctionalized magnetic support through a wet impregnation method. This nanomaterial proved to be highly active and magnetically retrievable in room-temp. hydrogenation of various arenes under atm. hydrogen pressure in neat water. The catalytic applications were extended to the selective redn. of nitroarenes into aniline, a relevant synthon for industrial applications, and to the dechlorination of chloroarenes, which could be of great interest for wastewater treatment. Finally, these Rh0@γ-Fe2O3 nanocomposites were compared to their Pd analogs, thus affording complementary catalytic activities.
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      (n) Shi, J.; Zhao, M.; Wang, Y.; Fu, J.; Lu, X.; Hou, Z. Upgrading of aromatic compounds in bio-oil over ultrathin graphene encapsulated Ru nanoparticles. J. Mater. Chem. A 2016, 4, 5842– 5848,  DOI: 10.1039/C6TA01317A
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      3n
      Upgrading of aromatic compounds in bio-oil over ultrathin graphene encapsulated Ru nanoparticles
      Shi, Juanjuan; Zhao, Mengsi; Wang, Yingyu; Fu, Jie; Lu, Xiuyang; Hou, Zhaoyin
      Journal of Materials Chemistry A: Materials for Energy and Sustainability (2016), 4 (16), 5842-5848CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
      Fast pyrolysis of biomass for bio-oil prodn. is a direct route to renewable liq. fuels, but raw bio-oil must be upgraded in order to remove easily polymd. compds. (such as phenols and furfurals). Herein, a synthesis strategy for graphene encapsulated Ru nanoparticles (NPs) on carbon sheets (denoted as Ru@G-CS) and their excellent performance for the upgrading of raw bio-oil were reported. Ru@G-CS composites were prepd. via the direct pyrolysis of mixed glucose, melamine and RuCl3 at varied temps. (500-800 °C). Characterization indicated that very fine Ru NPs (2.5 ± 1.0 nm) that were encapsulated within 1-2 layered N-doped graphene were fabricated on N-doped carbon sheets (CS) in Ru@G-CS-700 (pyrolysis at 700 °C). And the Ru@G-CS-700 composite was highly active and stable for hydrogenation of unstable components in bio-oil (31 samples including phenols, furfurals and aroms.) even in aq. media under mild conditions. This work provides a new protocol to the utilization of biomass, esp. for the upgrading of bio-oil.
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      (o) Sun, B.; Süss-Fink, G. Ruthenium-catalyzed hydrogenation of aromatic amino acids in aqueous solution. J. Organomet. Chem. 2016, 81– 86,  DOI: 10.1016/j.jorganchem.2015.09.011
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      3o
      Ruthenium-catalyzed hydrogenation of aromatic amino acids in aqueous solution
      Sun, Bing; Suss-Fink, Georg
      Journal of Organometallic Chemistry (2016), 812 (), 81-86CODEN: JORCAI; ISSN:0022-328X. (Elsevier B.V.)
      A catalyst contg. metallic ruthenium nanoparticles intercalated in hectorite (nanoRu@hectorite) was found to catalyze the hydrogenation of arom. amino acids in aq. soln. Thus, L-phenylalanine and L-phenylglycine can be converted exclusively into the corresponding L-cyclohexyl amino acids with retention of chirality under mild conditions (60 °C, 40 bar), conversion and selectivity being superior to 99%. The catalyst can be recycled and reused at least three times without loss in activity and selectivity.
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      (p) Baghbanian, S. M.; Farhang, M.; Vahdat, S. M.; Tajbakhsh, M. Hydrogenation of arenes, nitroarenes, and alkenes catalyzed by rhodium nanoparticles supported on natural nanozeolite clinoptilolite. J. Mol. Catal. A: Chem. 2015, 128– 136,  DOI: 10.1016/j.molcata.2015.06.029
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      3p
      Hydrogenation of arenes, nitroarenes, and alkenes catalyzed by rhodium nanoparticles supported on natural nanozeolite clinoptilolite
      Baghbanian, Seyed Meysam; Farhang, Maryam; Vahdat, Seyed Mohammad; Tajbakhsh, Mahmood
      Journal of Molecular Catalysis A: Chemical (2015), 407 (), 128-136CODEN: JMCCF2; ISSN:1381-1169. (Elsevier B.V.)
      Nanozeolite clinoptilolite supported rhodium nanoparticles (Rh/NZ-CP) has been prepd. and characterized by a variety of techniques, including XRD, BET, TEM, EDX, ICP-OES and XPS anal. This nanomaterial contains 2 wt% Rh in the range of 5-20 nm metallic nanoparticles distributed on nanozeolite. The catalytic performance of Rh/NZ-CP was evaluated by the hydrogenation of arenes, nitroarenes, and alkenes under moderate reaction conditions. The prepd. nanocatalyst can be facilely recovered and reused many times without significant decrease in activity and selectivity. The high catalytic activity, thermal stability and reusability, simple recovery and eco-friendly nature make present catalyst as a unique catalytic system, which is particularly attractive in green chem.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXht1Gmtb7P&md5=2bef56525518a882fa2c671dcdbfcb1c
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      (q) Martínez-Prieto, L. M.; Urbaneja, C.; Palma, P.; Cámpora, J.; Philippot, K.; Chaudret, B. A betaine adduct of N-heterocyclic carbene and carbodiimide, an efficient ligand to produce ultra-small ruthenium nanoparticles. Chem. Commun. 2015, 51, 4647– 4650,  DOI: 10.1039/C5CC00211G
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      3q
      A betaine adduct of N-heterocyclic carbene and carbodiimide, an efficient ligand to produce ultra-small ruthenium nanoparticles
      Martinez-Prieto, L. M.; Urbaneja, C.; Palma, P.; Campora, J.; Philippot, K.; Chaudret, B.
      Chemical Communications (Cambridge, United Kingdom) (2015), 51 (22), 4647-4650CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      The betaine adduct of N-heterocyclic carbene and carbodiimide ICy+·4-MeC6H4N:CN-C6H4Me-4 (ICy = 1,3-dicyclohexyl-2-imidazolylidene) was found to be a very efficient ligand and stabilizing agent to prep. very small (1-1.3 nm) ruthenium nanoparticles (RuNPs). The ligand is attached to ruthenium cluster surface by its carbodiimide nitrogens, carrying a delocalized neg. charge. The coordination of the ligand on the metal surface takes place through the carbodiimide moiety. The resulting RuNPs led to decarbonylation of THF and showed size selectivity for styrene hydrogenation.
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      .
      (r) Kang, X.; Zhang, J.; Shang, W.; Wu, T.; Zhang, P.; Han, B.; Wu, Z.; Mo, G.; Xing, X. One-Step Synthesis of Highly Efficient Nanocatalysts on the Supports with Hierarchical Pores Using Porous Ionic Liquid-Water Gel. J. Am. Chem. Soc. 2014, 136, 3768– 3771,  DOI: 10.1021/ja5001517
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      3r
      One-Step Synthesis of Highly Efficient Nanocatalysts on the Supports with Hierarchical Pores Using Porous Ionic Liquid-Water Gel
      Kang, Xinchen; Zhang, Jianling; Shang, Wenting; Wu, Tianbin; Zhang, Peng; Han, Buxing; Wu, Zhonghua; Mo, Guang; Xing, Xueqing
      Journal of the American Chemical Society (2014), 136 (10), 3768-3771CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Stable porous ionic liq.-water gel induced by inorg. salts was created for the first time. The porous gel was used to develop a one-step method to synthesize supported metal nanocatalysts. Au/SiO2, Ru/SiO2, Pd/Cu(2-pymo)2 metal-org. framework (Cu-MOF), and Au/polyacrylamide (PAM) were synthesized, in which the supports had hierarchical meso- and macropores, the size of the metal nanocatalysts could be small (<1 nm), and the size distribution was narrow even when the metal loading amt. was as high as 8 wt. %. The catalysts were extremely active, selective, and stable for oxidative esterification of benzyl alc. to Me benzoate, benzene hydrogenation to cyclohexane, and oxidn. of benzyl alc. to benzaldehyde because they combined the advantages of the nanocatalysts of small size and hierarchical porosity of the supports. In addn., this method is simple.
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      (s) Maegawa, T.; Akashi, A.; Yaguchi, K.; Iwasaki, Y.; Shigetsura, M.; Monguchi, Y.; Sajiki, H. Efficient and Practical Arene Hydrogenation by Heterogeneous Catalysts under Mild Conditions. Chem. - Eur. J. 2009, 15, 6953– 6963,  DOI: 10.1002/chem.200900361
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      3s
      Efficient and Practical Arene Hydrogenation by Heterogeneous Catalysts under Mild Conditions
      Maegawa, Tomohiro; Akashi, Akira; Yaguchi, Kiichiro; Iwasaki, Yohei; Shigetsura, Masahiro; Monguchi, Yasunari; Sajiki, Hironao
      Chemistry - A European Journal (2009), 15 (28), 6953-6963, S6953/1-S6953/85CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      An efficient and practical arene hydrogenation procedure based on the use of heterogeneous platinum group catalysts has been developed. Rh/C is the most effective catalyst for the hydrogenation of the arom. ring, which can be conducted in iPrOH under neutral conditions and at ordinary to medium H2 pressures (<10 atm). A variety of arenes such as alkylbenzenes, benzoic acids, pyridines, furans, are hydrogenated to the corresponding cyclohexyl and heterocyclic compds. in good to excellent yields. The use of Ru/C, less expensive than Rh/C, affords an effective and practical method for the hydrogenation of arenes including phenols. Both catalysts can be reused several times after simple filtration without any significant loss of catalytic activity.
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      (t) Maegawa, T.; Akashi, A.; Sajiki, H. A Mild and Facile Method for Complete Hydrogenation of Aromatic Nuclei in Water. Synlett 2006, 9, 1440– 1442,  DOI: 10.1055/s-2006-939719
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    4. 4

      For selected papers, see:

      (a) Jie, X.; Gonzalez-Cortes, S.; Xiao, T.; Wang, J.; Yao, B.; Slocombe, D. R.; Al-Megren, H. A.; Dilworth, J. R.; Thomas, J. M.; Edwards, P. P. Rapid Production of High-Purity Hydrogen Fuel through Microwave-Promoted Deep Catalytic Dehydrogenation of Liquid Alkanes with Abundant Metals. Angew. Chem., Int. Ed. 2017, 56, 10170– 10173,  DOI: 10.1002/anie.201703489
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      4a
      Rapid Production of High-Purity Hydrogen Fuel through Microwave-Promoted Deep Catalytic Dehydrogenation of Liquid Alkanes with Abundant Metals
      Jie, Xiangyu; Gonzalez-Cortes, Sergio; Xiao, Tiancun; Wang, Jiale; Yao, Benzhen; Slocombe, Daniel R.; Al-Megren, Hamid A.; Dilworth, Jonathan R.; Thomas, John M.; Edwards, Peter P.
      Angewandte Chemie, International Edition (2017), 56 (34), 10170-10173CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Hydrogen as an energy carrier promises a sustainable energy revolution. However, one of the greatest challenges for any future hydrogen economy is the necessity for large scale hydrogen prodn. not involving concurrent CO2 prodn. The high intrinsic hydrogen content of liq.-range alkane hydrocarbons (including diesel) offers a potential route to CO2-free hydrogen prodn. through their catalytic deep dehydrogenation. We report here a means of rapidly liberating high-purity hydrogen by microwave-promoted catalytic dehydrogenation of liq. alkanes using Fe and Ni particles supported on silicon carbide. A H2 prodn. selectivity from all evolved gases of some 98 %, is achieved with less than a fraction of a percent of adventitious CO and CO2. The major co-product is solid, elemental carbon.
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      .
      (b) Gonzalez-Cortes, S.; Slocombe, D. R.; Xiao, T.; Aldawsari, A.; Yao, B.; Kuznetsov, V. L.; Leberti, E.; Kirkland, A. I.; Alkinani, M. S.; Al-Megren, H. A.; Thomas, J. M.; Edwards, P. P. Wax: A benign hydrogen-storage material that rapidly releases H2-rich gases through microwave-assisted catalytic decomposition. Sci. Rep. 2016, 6, 35315  DOI: 10.1038/srep35315
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      4b
      Wax: A benign hydrogen-storage material that rapidly releases H2-rich gases through microwave-assisted catalytic decomposition
      Gonzalez-Cortes, S.; Slocombe, D. R.; Xiao, T.; Aldawsari, A.; Yao, B.; Kuznetsov, V. L.; Liberti, E.; Kirkland, A. I.; Alkinani, M. S.; Al-Megren, H. A.; Thomas, J. M.; Edwards, P. P.
      Scientific Reports (2016), 6 (), 35315CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)
      Hydrogen is often described as the fuel of the future, esp. for application in hydrogen powered fuel-cell vehicles (HFCV's). However, its widespread implementation in this role has been thwarted by the lack of a lightwt., safe, on-board hydrogen storage material. Here we show that benign, readily-available hydrocarbon wax is capable of rapidly releasing large amts. of hydrogen through microwave-assisted catalytic decompn. This discovery offers a new material and system for safe and efficient hydrogen storage and could facilitate its application in a HFCV. Importantly, hydrogen storage materials made of wax can be manufd. through completely sustainable processes utilizing biomass or other renewable feedstocks.
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      .
      (c) Susanti, R. F.; Dianningrum, L. W.; Yum, T.; Kim, Y.; Lee, Y.-W.; Kim, J. High-yield hydrogen production by supercritical water gasification of various feedstocks: Alcohols, glucose, glycerol and long-chain alkanes. Chem. Eng. Res. Des. 2014, 92, 1834– 1844,  DOI: 10.1016/j.cherd.2014.01.003
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      4c
      High-yield hydrogen production by supercritical water gasification of various feedstocks: Alcohols, glucose, glycerol and long-chain alkanes
      Susanti, Ratna F.; Dianningrum, Laras W.; Yum, Taewoo; Kim, Yunje; Lee, Youn-Woo; Kim, Jaehoon
      Chemical Engineering Research and Design (2014), 92 (10), 1834-1844CODEN: CERDEE; ISSN:1744-3563. (Elsevier B.V.)
      Continuous supercrit. water gasification (SCWG) of various feedstocks of C1-C16 was conducted to produce hydrogen-rich gas. These feedstocks represent model compds. of biomass such as methanol/ethanol (alc.-type), glucose and glycerol (byproducts of biodiesel synthesis), and model compds. of petroleum fuels such as iso-octane/n-octane (gasoline), n-decane/n-dodecane (jet fuels) and n-hexadecane (diesel). Almost complete gasification of all the feedstocks was achieved at 25 MPa, 740 °C and 10 wt% with low total org. carbon values of their liq. effluents. The hydrogen gas yields of each feedstock were very similar to the theor. equil. yields estd. by Gibbs free energy minimization. SCWG at different gasification temps. (650 and 740 °C) and concns. (10 and 20 wt%) revealed that methanol and ethanol (alcs.), the simple oxygenated hydrocarbons, were easier to be gasified, producing negligible amts. of liq. products, when compared with long-chain hydrocarbons (iso-octane and n-decane) under the identical conditions. When the feedstock concn. was increased from 10 to 20 wt%, the equil. hydrogen ratio from iso-octane gasification decreased from 1.02 to 0.79 while that of n-decane increased from 1.12 to 1.50, implying that a branched hydrocarbon may be more resistant to gasification in supercrit. water.
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      (d) Ahmed, S.; Aitani, A.; Rahman, F.; Al-Dawood, A.; Al-Muhaish, F. Decomposition of hydrocarbons to hydrogen and carbon. Appl. Catal., A 2009, 359, 1– 24,  DOI: 10.1016/j.apcata.2009.02.038
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      4d
      Decomposition of hydrocarbons to hydrogen and carbon
      Ahmed, Shakeel; Aitani, Abdullah; Rahman, Faizur; Al-Dawood, Ali; Al-Muhaish, Fahad
      Applied Catalysis, A: General (2009), 359 (1-2), 1-24CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
      A review of technologies and catalysts pertaining to the catalytic decompn. of hydrocarbons for the CO2-free generation of H for fuel cell applications through single-step cracking (decompn., decarbonization, dehydrogenation, pyrolysis, splitting, or dissocn.) of hydrocarbons. The options for hydrocarbon decompn. to H and C are discussed and categorized. This decompn. helps to reduce green house gases by co-producing valuable C products such as C black or graphite-like C (C nanotubes or C filaments). The catalytic approach comprises metal and C-based catalysts while plasma-based decompn. depends on thermal or nonthermal methods. Almost all the proposed processes are applicable to a variety of gaseous and liq. hydrocarbon fuels and some of these processes can potentially produce a stream of high-purity H. There have been successful attempts to use catalysts to decrease the max. temp. of the thermal decompn. of hydrocarbons. Common catalysts used are noble and transition metals such as Ni, Fe, Pd, Co and Mo supported on high surface-area ceramic substrates such as Al2O3 and SiO2. Several publications disclose the use of C-based materials as catalysts for decompn. of hydrocarbons into H2 and C. Other non-catalytic decompn. methods include non-thermal low-temp. plasmas such as RF, d.c. generators, microwave plasmatrons and arc plasma jet.
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    5. 5
      (a) Espro, C.; Gumina, B.; Szumelda, T.; Paone, E.; Mauriello, F. Catalytic transfer hydrogenolysis as an effective tool for the reductive upgrading of cellulose, hemicellulose, lignin, and their derived molecules. Catalysts 2018, 3, 313,  DOI: 10.3390/catal8080313
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      (b) Wang, D.; Astruc, D. The golden age of transfer hydrogenation. Chem. Rev. 2015, 115, 6621– 6686,  DOI: 10.1021/acs.chemrev.5b00203
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      5b
      The Golden Age of Transfer Hydrogenation
      Wang, Dong; Astruc, Didier
      Chemical Reviews (Washington, DC, United States) (2015), 115 (13), 6621-6686CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review on transfer hydrogenation using transition metal catalysts and organocatalysts.
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      (c) Gilkey, M. J.; Xu, B. Heterogeneous catalytic transfer hydrogenation as an effective pathway in biomass upgrading. ACS Catal. 2016, 6, 1420– 1436,  DOI: 10.1021/acscatal.5b02171
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      5c
      Heterogeneous Catalytic Transfer Hydrogenation as an Effective Pathway in Biomass Upgrading
      Gilkey, Matthew J.; Xu, Bingjun
      ACS Catalysis (2016), 6 (3), 1420-1436CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      A review is given. Reducing O content in biomass-derived feedstocks via hydrodeoxygenation (HDO) is a key step in their upgrading to fuels and valuable chems. Org. mols., e.g., alcs. and formic acid, can donate H to reduce the substrate in a process called catalytic transfer hydrogenation (CTH). Although it is practiced far less frequently than mol.-hydrogen-based HDO processes, CTH has been proven to be an efficient and selective strategy in biomass upgrading in the last two decades. We present a selective review of recent progress made in the upgrade of biomass-derived feedstocks through heterogeneous CTH, with a focus on the mechanistic interpretation. Hydrogenation and cleavage of C=O and C-O bonds, resp., are the 2 main categories of reactions discussed, owing to their importance in the HDO of biomass-derived feedstocks. On acid-base catalysts, Lewis acid-base pair sites, rather than a single acid or base site, mediate hydrogenation of carbonyl groups with alcs. as the H donor. While acid-base catalysts typically only catalyze the hydrogenation of carbonyl groups with alcs. as the H donor, metal-based catalysts are able to mediate both hydrogenation and hydrogenolysis reactions with either alcs. or formic acid. Several model reactions involving platform chems. in biomass upgrading, e.g., 5-hydroxymethylfurfural, levulinic acid, and glycerol, are used in the discussion to illustrate general trends. Because alcs. are typically both the H donor and the solvent, the donor and solvent effects are intertwined. Therefore, solvent effects are discussed primarily in the context of sugar isomerization and reactions with formic acid as the H donor, in which the solvent and H donor are 2 sep. species. Current challenges and opportunities of future research to develop CTH into a competitive and complementary strategy of the conventional mol.-H-based processes are also discussed.
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    6. 6
      (a) Paone, E.; Espro, C.; Pietropaolo, R.; Mauriello, F. Selective arene production form transfer hydrogenolysis of benzyl phenyl ether promoted by the coprecipitated Pd/Fe3O4 catalyst. Catal. Sci. Technol. 2016, 6, 7937– 7941,  DOI: 10.1039/C6CY01626J
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      6a
      Selective arene production from transfer hydrogenolysis of benzyl phenyl ether promoted by a co-precipitated Pd/Fe3O4 catalyst
      Paone, E.; Espro, C.; Pietropaolo, R.; Mauriello, F.
      Catalysis Science & Technology (2016), 6 (22), 7937-7941CODEN: CSTAGD; ISSN:2044-4753. (Royal Society of Chemistry)
      The catalytic transfer hydrogenolysis of benzyl Ph ether has been investigated using Pd/Fe3O4 as a heterogeneous catalyst and 2-propanol as a H-donor. After 90 min at 240°, the cleavage of the ether C-O bond occurs as the only reaction route without hydrogenation of the arom. ring.
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      .
      (b) Espro, C.; Gumina, B.; Paone, E.; Mauriello, F. Upgrading Lignocellulosic Biomasses: Hydrogenolysis of Platform Derived Molecules Promoted by Heterogeneous Pd-Fe Catalysts. Catalysts 2017, 7, 78,  DOI: 10.3390/catal7030078
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      6b
      Upgrading lignocellulosic biomasses: hydrogenolysis of platform derived molecules promoted by heterogeneous Pd-Fe catalysts
      Espro, Claudia; Gumina, Bianca; Paone, Emilia; Mauriello, Francesco
      Catalysts (2017), 7 (3), 78/1-78/36CODEN: CATACJ; ISSN:2073-4344. (MDPI AG)
      This review provides an overview of heterogeneous bimetallic Pd-Fe catalysts in the C-C and C-O cleavage of platform mols. such as C2-C6 polyols, furfural, phenol derivs. and arom. ethers that are all easily obtainable from renewable cellulose, hemicellulose and lignin (the major components of lignocellulosic biomasses). The interaction between palladium and iron affords bimetallic Pd-Fe sites (ensemble or alloy) that were found to be very active in several sustainable reactions including hydrogenolysis, catalytic transfer hydrogenolysis (CTH) and aq. phase reforming (APR) that will be highlighted. This contribution concs. also on the different synthetic strategies (incipient wetness impregnation, deposition-pptn., co-pptn.) adopted for the prepn. of heterogeneous Pd-Fe systems as well as on the main characterization techniques used (XRD, TEM, H2-TPR, XPS and EXAFS) in order to elucidate the key factors that influence the unique catalytic performances obsd.
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    7. 7
      (a) Sawama, Y.; Morita, K.; Yamada, T.; Nagata, S.; Yabe, Y.; Monguchi, Y.; Sajiki, H. Rhodium-on-carbon catalyzed hydrogen scavenger- and oxidant-free dehydrogenation of alcohols in aqueous media. Green Chem. 2014, 16, 3439– 3443,  DOI: 10.1039/c4gc00434e
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      7a
      Rhodium-on-carbon catalyzed hydrogen scavenger- and oxidant-free dehydrogenation of alcohols in aqueous media
      Sawama, Yoshinari; Morita, Kosuke; Yamada, Tsuyoshi; Nagata, Saori; Yabe, Yuki; Monguchi, Yasunari; Sajiki, Hironao
      Green Chemistry (2014), 16 (7), 3439-3443CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
      The efficient and catalytic dehydrogenation of alcs. is a clean approach for prepg. carbonyl compds. accompanied only by the generation of hydrogen gas. We have accomplished the heterogeneous rhodium-on-carbon catalyzed dehydrogenation of secondary, as well as primary, alcs. to the corresponding ketones and carboxylic acids in water under basic conditions.
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      (b) Sawama, Y.; Morita, K.; Asai, S.; Kozawa, M.; Tadokoro, S.; Nakajima, J.; Monguchi, Y.; Sajiki, H. Palladium on Carbon-Catalyzed Aqueous Transformation of Primary Alcohols to Carboxylic Acids Based on Dehydrogenation under Mildly Reduced Pressure. Adv. Synth. Catal. 2015, 357, 1205– 1210,  DOI: 10.1002/adsc.201401123
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      7b
      Palladium-on-Carbon-Catalyzed Aqueous Transformation of Primary Alcohols to Carboxylic Acids Based on Dehydrogenation under Mildly Reduced Pressure
      Sawama, Yoshinari; Morita, Kosuke; Asai, Shota; Kozawa, Masami; Tadokoro, Shinsuke; Nakajima, Junichi; Monguchi, Yasunari; Sajiki, Hironao
      Advanced Synthesis & Catalysis (2015), 357 (6), 1205-1210CODEN: ASCAF7; ISSN:1615-4150. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The catalytic dehydrogenation of alcs. to carbonyl products is a green sustainable oxidn. with no prodn. of waste except for hydrogen, which is an energy source. Addnl., a reusable heterogeneous catalyst is valuable from the viewpoint of process chem. and water is a green solvent. The palladium on carbon (Pd/C)-catalyzed dehydrogenation of primary alcs. to carboxylic acids in water was accomplished under a mildly reduced pressure (800 hPa). The reduced pressure was easily controlled by the vacuum controller of the rotary evaporator to remove the excess of generated hydrogen, which causes the redn. (reverse reaction) of aldehydes to alcs. (starting materials) and other undesirable side reactions. The present method is applicable to the reaction of various aliph. and benzylic alcs. to the corresponding carboxylic acids, and the Pd/C can be reused at least 5 times.
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    8. 8
      (a) Yasukawa, N.; Yokoyama, H.; Masuda, M.; Monguchi, Y.; Sajiki, H.; Sawama, Y. Highly-functionalized arene synthesis based on palladium on carbon-catalyzed aqueous dehydrogenation of cyclohexadienes and cyclohexenes. Green Chem. 2018, 20, 1213– 1217,  DOI: 10.1039/C7GC03819D
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      8a
      Highly-functionalized arene synthesis based on palladium on carbon-catalyzed aqueous dehydrogenation of cyclohexadienes and cyclohexenes
      Yasukawa, Naoki; Yokoyama, Hiroki; Masuda, Masahiro; Monguchi, Yasunari; Sajiki, Hironao; Sawama, Yoshinari
      Green Chemistry (2018), 20 (6), 1213-1217CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
      Transition metal-catalyzed dehydrogenation was a clean oxidn. method requiring no addnl. oxidants. A heterogeneous Pd/C-catalyzed aq. dehydrogenation of 1,4-cyclohexadienes and cyclohexenes to give the corresponding highly-functionalized arenes was described. Furthermore, various arenes were efficiently constructed in a one-pot manner via a Diels-Alder reaction followed by dehydrogenation.
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      .
      (b) Ichikawa, T.; Matsuo, T.; Tachikawa, T.; Yamada, T.; Yoshimura, T.; Yoshimura, M.; Takagi, Y.; Sawama, Y.; Sugiyama, J.; Monguchi, Y.; Sajiki, H. Microwave-Mediated Site-Selective Heating of Spherical-Carbon-Bead-Supported Platinum for the Continuous, Efficient Catalytic Dehydrogenative Aromatization of Saturated Cyclic Hydrocarbons. ACS Sustainable Chem. Eng. 2019, 7, 3052– 3061,  DOI: 10.1021/acssuschemeng.8b04655
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      8b
      Microwave-Mediated Site-Selective Heating of Spherical-Carbon-Bead-Supported Platinum for the Continuous, Efficient Catalytic Dehydrogenative Aromatization of Saturated Cyclic Hydrocarbons
      Ichikawa, Tomohiro; Matsuo, Tomohiro; Tachikawa, Takumu; Yamada, Tsuyoshi; Yoshimura, Takeo; Yoshimura, Masatoshi; Takagi, Yukio; Sawama, Yoshinari; Sugiyama, Jun-ichi; Monguchi, Yasunari; Sajiki, Hironao
      ACS Sustainable Chemistry & Engineering (2019), 7 (3), 3052-3061CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
      A microwave (MW)-assisted method for the continuous prodn. of hydrogen from methylcyclohexane using platinum on spherical carbon beads has been developed, and its application to the efficient dehydrogenative aromatization of fully satd. cyclic alkanes, including piperidines as representative heterocycles, has been studied. Effective dehydrogenation was achieved by the construction of a highly intense energy field, which acted as a reactive site, on the irradn. of the carbon beads (CB) support. The reaction could be carried out with only 10-W single-frequency MWs. The catalyst system could be used continuously for at least 12 h without any loss of catalyst activity. Dehydrogenative aromatization could also be catalyzed and simple cyclohexane derivs., as well as piperidine derivs. as representative N-heterocyclic alkanes, were tested.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXivFWmsw%253D%253D&md5=2d3bd8fa0ada99a3a515cf15b3697a8b
    9. 9
      (a) Sawama, Y.; Niikawa, M.; Yabe, Y.; Goto, R.; Kawajiri, T.; Marumoto, T.; Takahashi, T.; Itoh, M.; Sasai, Y.; Yamauchi, Y.; Kondo, S.; Kuzuya, M.; Itoh, M.; Monguchi, Y.; Sajiki, H. Stainless-Steel-Mediated Quantitative Hydrogen Generation from Water under Ball Milling Conditions. ACS Sustainable Chem. Eng. 2015, 3, 683– 689,  DOI: 10.1021/sc5008434
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      9a
      Stainless-Steel-Mediated Quantitative Hydrogen Generation from Water under Ball Milling Conditions
      Sawama, Yoshinari; Niikawa, Miki; Yabe, Yuki; Goto, Ryota; Kawajiri, Takahiro; Marumoto, Takahisa; Takahashi, Tohru; Itoh, Miki; Kimura, Yuuichi; Sasai, Yasushi; Yamauchi, Yukinori; Kondo, Shin-ichi; Kuzuya, Masayuki; Monguchi, Yasunari; Sajiki, Hironao
      ACS Sustainable Chemistry & Engineering (2015), 3 (4), 683-689CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
      A robust and quant. gaseous H generation method was developed in an effort to achieve efficient H2 generation derived from H2O. The present reaction could be achieved by a simple ball friction (milling) reaction of H2O using a planetary ball mill machine with a stainless-steel vessel and balls. It was mediated by metals as an element of stainless steel of the ball mill and also promoted by mechanochem. processing.
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      .
      (b) Sawama, Y.; Kawajiri, T.; Niikawa, M.; Goto, R.; Yabe, Y.; Takahashi, T.; Marumoto, T.; Itoh, M.; Kimura, Y.; Monguchi, Y.; Kondo, S.; Sajiki, H. Stainless-Steel Ball-Milling Method for Hydro-/Deutero-genation using H2O/D2O as a Hydrogen/Deuterium Source. ChemSusChem 2015, 8, 3773– 3776,  DOI: 10.1002/cssc.201501019
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      9b
      Stainless-Steel Ball-Milling Method for Hydro-/Deutero-genation using H2O/D2O as a Hydrogen/Deuterium Source
      Sawama, Yoshinari; Kawajiri, Takahiro; Niikawa, Miki; Goto, Ryota; Yabe, Yuki; Takahashi, Tohru; Marumoto, Takahisa; Itoh, Miki; Kimura, Yuuichi; Monguchi, Yasunari; Kondo, Shin-ichi; Sajiki, Hironao
      ChemSusChem (2015), 8 (22), 3773-3776CODEN: CHEMIZ; ISSN:1864-5631. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A one-pot continuous-flow method for hydrogen (deuterium) generation and subsequent hydrogenation (deuterogenation) was developed using a stainless-steel (SUS304)-mediated ball-milling approach. SUS304, esp. zero-valent Cr and Ni as constituents of the SUS304, and mechanochem. processing played crucial roles in the development of the reactions.
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      .
      (c) Sawama, Y.; Yasukawa, N.; Ban, K.; Goto, R.; Niikawa, M.; Monguchi, Y.; Itoh, M.; Sajiki, H. Stainless Steel-Mediated Hydrogen Generation from Alkanes and Diethyl Ether and Its Application for Arene Reduction. Org. Lett. 2018, 20, 2892– 2896,  DOI: 10.1021/acs.orglett.8b00931
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      9c
      Stainless Steel-Mediated Hydrogen Generation from Alkanes and Diethyl Ether and Its Application for Arene Reduction
      Sawama, Yoshinari; Yasukawa, Naoki; Ban, Kazuho; Goto, Ryota; Niikawa, Miki; Monguchi, Yasunari; Itoh, Miki; Sajiki, Hironao
      Organic Letters (2018), 20 (10), 2892-2896CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
      Hydrogen gas can be generated from simple alkanes (e.g., n-pentane, n-hexane, etc.) and di-Et ether (Et2O) by mechanochem. energy using a planetary ball mill (SUS304, Fritsch Pulverisette 7), and the use of stainless steel balls and vessel is an important factor to generate the hydrogen. The redn. of org. compds. was also accomplished using the in-situ-generated hydrogen. While the use of pentane as the hydrogen source facilitated the redn. of the olefin moieties, the arene redn. could proceed using Et2O. Within the components (Fe, Cr, Ni, etc.) of the stainless steel, Cr was the metal factor for the hydrogen generation from the alkanes and Et2O, and Ni metal played the role of the hydrogenation catalyst.
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    10. 10
      (a) Sawama, Y.; Yabe, Y.; Shigetsura, M.; Yamada, T.; Nagata, S.; Fujiwara, Y.; Maegawa, T.; Monguchi, Y.; Sajiki, H. Platinum on Carbon-Catalyzed Hydrodefluorination of Fluoroarenes using Isopropyl Alcohol-Water-Sodium Carbonate Combination. Adv. Synth. Catal. 2012, 354, 777– 782,  DOI: 10.1002/adsc.201100927
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      10a
      Platinum on Carbon-Catalyzed Hydrodefluorination of Fluoroarenes using Isopropyl Alcohol-Water-Sodium Carbonate Combination
      Sawama, Yoshinari; Yabe, Yuki; Shigetsura, Masahiro; Yamada, Tsuyoshi; Nagata, Saori; Fujiwara, Yuta; Maegawa, Tomohiro; Monguchi, Yasunari; Sajiki, Hironao
      Advanced Synthesis & Catalysis (2012), 354 (5), 777-782CODEN: ASCAF7; ISSN:1615-4150. (Wiley-VCH Verlag GmbH & Co. KGaA)
      We have developed a platinum on carbon-iso-Pr alc.-catalyzed and widely applicable defluorination method for fluoroarenes, e.g., 4-FC6H4Ph, and the addn. of water and sodium carbonate efficiently accelerated the reaction. The defluorination readily occurred under the reaction conditions in comparison with the dehalogenation of other arom. halides (fluorine>chlorine>bromine»iodine).
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      .
      (b) Sawama, Y.; Mori, M.; Yamada, T.; Monguchi, Y.; Sajiki, H. Hydrogen Self-Sufficient Arene Reduction to Cyclohexane Derivatives Using a Combination of Platinum on Carbon and 2-Propanol. Adv. Synth. Catal. 2015, 357, 3667– 3670,  DOI: 10.1002/adsc.201500263
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      10b
      Hydrogen Self-Sufficient Arene Reduction to Cyclohexane Derivatives Using a Combination of Platinum on Carbon and 2-Propanol
      Sawama, Yoshinari; Mori, Misato; Yamada, Tsuyoshi; Monguchi, Yasunari; Sajiki, Hironao
      Advanced Synthesis & Catalysis (2015), 357 (16-17), 3667-3670CODEN: ASCAF7; ISSN:1615-4150. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Various arenes have been hydrogenated using platinum on carbon in a 2-propanol-aq. mixed solvent at 100 °C without the addn. of flammable hydrogen gas to give the corresponding cyclohexane derivs. 2-Propanol plays a role as an efficient hydrogen source based on the platinum on carbon-catalyzed dehydrogenation.
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    11. 11
      (a) Wang, H.; Krier, J. M.; Zhu, Z.; Melaet, G.; Wang, Y.; Kennedy, G.; Alayoglu, S.; An, K.; Somorjai, G. A. Promotion of Hydrogenation of Organic Molecules by Incorporating Iron into Platinum Nanoparticle Catalysts: Displacement of Inactive Reaction Intermediates. ACS Catal. 2013, 3, 2371– 2375,  DOI: 10.1021/cs400579j
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      11a
      Promotion of Hydrogenation of Organic Molecules by Incorporating Iron into Platinum Nanoparticle Catalysts: Displacement of Inactive Reaction Intermediates
      Wang, Hailiang; Krier, James M.; Zhu, Zhongwei; Melaet, Gerome; Wang, Yihai; Kennedy, Griffin; Alayoglu, Selim; An, Kwangjin; Somorjai, Gabor A.
      ACS Catalysis (2013), 3 (10), 2371-2375CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      We characterize the surface chem. states of reactants and catalysts under reaction conditions to elucidate the compn. effect of platinum-iron bimetallic nanoparticles on catalytic hydrogenation of org. mols. The catalytic hydrogenation of ethylene is drastically accelerated on the surface of 2 nm PtFe bimetallic nanoparticles as compared to pure Pt. Sum frequency generation (SFG) vibrational spectroscopy indicates that incorporation of Fe into Pt nanoparticle catalysts weakens the adsorption of ethylidyne, an inactive spectator species, on the catalyst surface. Similarly, the turnover frequency of cyclohexene hydrogenation is also significantly enhanced by incorporating Fe into Pt nanoparticle catalysts. Ambient-pressure XPS (AP-XPS) reveals the surface compn. and oxidn. states of the PtFe nanoparticles under reaction conditions. The oxidn. state distribution of Fe responded to the gas atm. and the probing depth, whereas the Pt remained largely metallic in all probing conditions. This work represents a mol. level correlation between catalyst structure and catalytic performance.
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      .
      (b) Liu, Z.; Tan, X.; Li, J.; Lv, C. Easy synthesis of bimetal PtFe-containing ordered mesoporous carbons and their use as catalysts for selective cinnamaldehyde hydrogenation. New J. Chem. 2013, 37, 1350– 1357,  DOI: 10.1039/c3nj40946e
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      11b
      Easy synthesis of bimetal PtFe-containing ordered mesoporous carbons and their use as catalysts for selective cinnamaldehyde hydrogenation
      Liu, Zhi; Tan, Xiuli; Li, Jia; Lv, Cong
      New Journal of Chemistry (2013), 37 (5), 1350-1357CODEN: NJCHE5; ISSN:1144-0546. (Royal Society of Chemistry)
      This work focuses on the prepn. and characterization of bimetal PtFe-contg. ordered mesoporous carbon (PtFe-OMC) materials with different Pt/Fe ratios and their use as the catalysts in selective cinnamaldehyde hydrogenation. The carbon materials were synthesized by means of an easy one-pot org.-org. self-assembly strategy using H2PtCl6·6H2O and Fe(NO3)3·9H2O as the metal precursors. All the samples were characterized by nitrogen adsorption-desorption, x-ray diffraction, XPS, temp. programmed redn., and TEM, and evaluated for catalytic cinnamaldehyde hydrogenation at various temps. and H2 pressures. The results showed that the Pt-Fe alloy nanoparticles were highly dispersed in the OMC matrix, and the presence of Fe resulted in charge-transfer, and thus, enhanced greatly the selective cinnamaldehyde hydrogenation of the Pt catalyst towards cinnamyl alc.
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      .
      (c) Lee, J.; Kim, Y. T.; Huber, G. W. Aqueous-phase hydrogenation and hydrodeoxygenation of biomass-derived oxygenates with bimetallic catalysts. Green Chem. 2014, 16, 708– 718,  DOI: 10.1039/c3gc41071d
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      11c
      Aqueous-phase hydrogenation and hydrodeoxygenation of biomass-derived oxygenates with bimetallic catalysts
      Lee, Jechan; Kim, Yong Tae; Huber, George W.
      Green Chemistry (2014), 16 (2), 708-718CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
      The reaction rate on a per site basis for aq.-phase hydrogenation (APH) of propanal, xylose, and furfural was measured over various alumina-supported bimetallic catalysts (Pd-Ni, Pd-Co, Pd-Fe, Ru-Ni, Ru-Co, Ru-Fe, Pt-Ni, Pt-Co, and Pt-Fe) using a high-throughput reactor (HTR). The results in this paper demonstrate that the activity of bimetallic catalysts for hydrogenation of a carbonyl group can be 110 times higher than monometallic catalysts. The addn. of Fe to a Pd catalyst increased the activity for hydrogenation of propanal, xylose, and furfural. The Pd1Fe3 catalyst had the highest reaction rate for APH of propanal among all catalysts tested in the HTR. The addn. of Fe to the Pd catalyst increased the reaction rate for xylose hydrogenation by a factor of 51, compared to the monometallic Pd catalyst. However, no bimetallic catalyst tested in this study was more active than the monometallic Ru catalyst for hydrogenation of xylose. The Pd1Fe3 catalyst had the highest reaction rate for APH of furfural, which was 9 times higher than the rate of the Pd catalyst. The Pd1Fe3/Zr-P, a bimetallic bifunctional catalyst, was 14 times more active on a per site basis than a Pd/Zr-P catalyst for aq.-phase hydrodeoxygenation (HDO) of sorbitol in a continuous flow reactor. The addn. of Fe to the Pd catalyst increased the rate of C-C cleavage reactions and promoted the conversion of sorbitan and isosorbide in HDO of sorbitol. Pd1Fe3/Zr-P also had a higher yield of gasoline-range products than the Pd/Zr-P catalyst.
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      .
      (d) Liu, L.; Lou, H.; Chen, M. Selective hydrogenation of furfural over Pt based and Pd based bimetallic catalysts supported on modified multiwalled carbon nanotubes (MWNT). Appl. Catal., A 2018, 550, 1– 10,  DOI: 10.1016/j.apcata.2017.10.003
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      11d
      Selective hydrogenation of furfural over Pt based and Pd based bimetallic catalysts supported on modified multiwalled carbon nanotubes (MWNT)
      Liu, Lujie; Lou, Hui; Chen, Min
      Applied Catalysis, A: General (2018), 550 (), 1-10CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
      Nano-Pt and Nano-Pd particles were introduced to modified multiwalled carbon nanotubes via co-impregnation method for hydrogenation of furfural in liq. phase using ethanol as a solvent. Different transition metal (Cr, Mn, Fe, Co, Ni) was used as promoters using Pt/MWNT and Pd/MWNT catalysts and various supports were also compared to further investigate the hydrogenation process of furfural. Among the catalysts investigated, Pt-Fe/MWNT (Pt: 0.5 wt%) showed highest conversion and selectivity to furfuryl alc. (yield of 87.4%), while Pd-Ni/MWNT (Pd: 0.5 wt%) catalysts exhibited the best catalytic performance (83.3% yield of tetrahydrofurfuryl alc.) under the optimized conditions of 30 bar hydrogen and 5 h, at 100 and 130 °C, resp. Synergistic effect of bimetallic catalysts has been utilized to improve catalytic activity and stability. The extremely active for the selective hydrogenation of furfural over Pt-Fe/MWNT and Pd-Ni/MWNT catalyst might be attributed to active crystal planes exposed over Pt and Pd promoted by Fe and Ni. Catalysts have shown stable activity and selectivity after 5 cycles using Pt-Fe/MWNT and Pd-Ni/MWNT catalysts. Moreover, we suggest that acid sites of conventional supports might have an impact on furfural conversion.
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    12. 12
      (a) Nakamula, I.; Yamanoi, Y.; Imaoka, T.; Yamamoto, K.; Nishihara, H. A Uniform Bimetallic Rhodium/Iron Nanoparticle Catalyst for the Hydrogenation of Olefins and Nitroarenes. Angew. Chem., Int. Ed. 2011, 50, 5830– 5833,  DOI: 10.1002/anie.201102836
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      12a
      A Uniform Bimetallic Rhodium/Iron Nanoparticle Catalyst for the Hydrogenation of Olefins and Nitroarenes
      Nakamula, Ikuse; Yamanoi, Yoshinori; Imaoka, Takane; Yamamoto, Kimihisa; Nishihara, Hiroshi
      Angewandte Chemie, International Edition (2011), 50 (26), 5830-5833, S5830/1-S5830/5CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Relative to the catalytic activity of pure Rh nanoparticles in a dendrimer cage, Rh/Fe bimetallic nanoparticles in dendrimers have improved catalytic activity towards the hydrogenation of olefins, and unlike Wilkinson catalyst could catalyze nitroarene hydrogenation.
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      .
      (b) Kim, J. K.; Lee, J. K.; Kang, K. H.; Lee, J. W.; Song, I. K. Catalytic decomposition of phenethyl phenyl ether to aromatics over Pd–Fe bimetallic catalysts supported on ordered mesoporous carbon. J. Mol. Catal. A: Chem. 2015, 410, 184– 192,  DOI: 10.1016/j.molcata.2015.09.023
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      12b
      Catalytic decomposition of phenethyl phenyl ether to aromatics over Pd-Fe bimetallic catalysts supported on ordered mesoporous carbon
      Kim, Jeong Kwon; Lee, Jong Kwon; Kang, Ki Hyuk; Lee, Jong Won; Song, In Kyu
      Journal of Molecular Catalysis A: Chemical (2015), 410 (), 184-192CODEN: JMCCF2; ISSN:1381-1169. (Elsevier B.V.)
      A series of bimetallic Pd-Fe catalysts supported on ordered mesoporous carbon (denoted as Pd1-FeX/OMC) were prepd. with a variation Fe/Pd molar ratio (X), and they were applied to the catalytic decompn. of phenethyl Ph ether to aroms. Phenethyl Ph ether was used as a lignin model compd. for representing β-O-4 linkage in lignin. The effect of Fe/Pd molar ratio on the catalytic activities and physicochem. properties of bimetallic Pd1-FeX/OMC catalysts was investigated. It was found that cryst. phase, reducibility, chem. state, and electronic property of Pd1-FeX/OMC catalysts were strongly influenced by Fe/Pd molar ratio. In particular, modified electronic property derived from the interaction between Pd and Fe significantly changed the hydrogen adsorption ability and bimetallic structure of the catalysts. Conversion of phenethyl Ph ether continuously decreased with increasing Fe/Pd molar ratio, whereas selectivity for aroms. increased and then became almost const. with increasing Fe/Pd molar ratio. As a consequence, yield for aroms. showed a volcano-shaped trend with respect to Fe/Pd molar ratio. Catalytic performance of Pd1-FeX/OMC catalysts was closely related to the hydrogen adsorption ability and bimetallic structure of the catalysts. Among the catalysts tested, Pd1-Fe0.7/OMC catalyst with moderate hydrogen adsorption ability and with bimetallic structure of Pd1Fe0.7 compn. showed the highest yield for aroms. Thus, an optimal Fe/Pd molar ratio was required to achieve max. prodn. of aroms. through selective cleavage of C-O bond in phenethyl Ph ether over Pd1-FeX/OMC catalysts.
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      .
      (c) Wang, R.; Tang, T.; Huang, K.; Zou, M.; Tao, X.; Yin, H.; Lin, Z.; Dang, Z.; Li, G. Debromination of polybrominated biphenyls (PBBs) by zero valent metals and iron-based bimetallic particles: Mechanisms, pathways and predicting descriptor. Chem. Eng. J. 2018, 351, 773– 781,  DOI: 10.1016/j.cej.2018.06.149
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      12c
      Debromination of polybrominated biphenyls (PBBs) by zero valent metals and iron-based bimetallic particles: Mechanisms, pathways and predicting descriptor
      Wang, Rui; Tang, Ting; Huang, Kaibo; Zou, Mengyao; Tao, Xueqin; Yin, Hua; Lin, Zhang; Dang, Zhi; Lu, Guining
      Chemical Engineering Journal (Amsterdam, Netherlands) (2018), 351 (), 773-781CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
      Polybrominated biphenyls (PBBs) are toxic and persistent brominated flame retardant. Yet their debromination by zero valent metal (ZVM) or iron based bimetals has received far less attention. Here we reported the kinetics and debromination pathways of PBBs in nanoscale zerovalent iron (n-ZVI), microscale zerovalent zinc (m-ZVZ), n-ZVI/Ag and n-ZVI/Pd systems. The results show that the singly occupied MO (SOMO) of PBB anion can be well correlated with the debromination pathways of PBBs by n-ZVI, which verify its ability to predict their debromination pathways through electron transfer (e-transfer) mechanism. We also found that the reaction rates of PBBs in m-ZVZ, n-ZVI/Ag and n-ZVI/Pd systems are much faster than that in n-ZVI system, and the debromination pathways of PBBs in n-ZVI, m-ZVZ and n-ZVI/Ag are exactly the same, suggesting that n-ZVI/Ag debrominate PBBs through an e-transfer mechanism. However, Pd was found to be able to utilize H2 to debrominate PBBs and the debromination pathways of PBBs in Pd-H2 system was the same to those in n-ZVI/Pd system, but was partially different from those in n-ZVI, m-ZVZ and n-ZVI/Ag systems, suggesting that n-ZVI/Pd debrominate PBBs through a H-atom transfer mechanism.
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    13. 13
      (a) Sawama, Y.; Yamada, T.; Yabe, Y.; Morita, K.; Shibata, K.; Shigetsura, M.; Monguchi, Y.; Sajiki, H. Platinum on carbon-catalyzed H-D exchange reaction of aromatic nuclei due to isopropyl alcohol-mediated self-activation of platinum metal in deuterium oxide. Adv. Synth. Catal. 2013, 355, 1529– 1539,  DOI: 10.1002/adsc.201201102
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      13a
      Platinum on Carbon-Catalyzed H-D Exchange Reaction of Aromatic Nuclei due to Isopropyl Alcohol-Mediated Self-Activation of Platinum Metal in Deuterium Oxide
      Sawama, Yoshinari; Yamada, Tsuyoshi; Yabe, Yuki; Morita, Kosuke; Shibata, Kyoshiro; Shigetsura, Masahiro; Monguchi, Yasunari; Sajiki, Hironao
      Advanced Synthesis & Catalysis (2013), 355 (8), 1529-1534CODEN: ASCAF7; ISSN:1615-4150. (Wiley-VCH Verlag GmbH & Co. KGaA)
      An efficient and simple deuteration method of arenes using the platinum on carbon-iso-Pr alc.-cyclohexane-deuterium oxide combination under hydrogen gas-free conditions was accomplished. Since the hydrogen-deuterium exchange reaction cannot be promoted without iso-Pr alc., zerovalent platinum metal (on carbon) is self-activated by the in situ-generated very low amt. of hydrogen or hydrogen-deuterium gas derived from iso-Pr alc. or iso-Pr alc.-d1. Deuterium-labeled compds. with high deuterium contents can be easily isolated by the filtration of platinum on carbon and simple extn. The present hydrogen gas-free method is safe from the viewpoint of process chem. and various arenes possessing a variety of reducible functionalities within the mol. could be effectively and directly deuterium-labeled without undesired redn.
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      .
      (b) Sawama, Y.; Park, K.; Yamada, T.; Sajiki, H. New gateways to the platinum group metal-catalyzed direct deuterium-labeling method utilizing hydroten as a catalyst activator. Chem. Pharm. Bull. 2018, 66, 21– 28,  DOI: 10.1248/cpb.c17-00222
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      13b
      New gateways to the platinum group metal-catalyzed direct deuterium-labeling method utilizing hydrogen as a catalyst activator
      Sawama, Yoshinari; Park, Kwihwan; Yamada, Tsuyoshi; Sajiki, Hironao
      Chemical & Pharmaceutical Bulletin (2018), 66 (1), 21-28CODEN: CPBTAL; ISSN:0009-2363. (Pharmaceutical Society of Japan)
      A review. This review summarized the recent advances in the direct deuteration of sugar, satd. fatty acid and arene derivs. using heterogeneous platinum group metal on carbon catalyst. In this review, the direct activation method of catalysts using in situ-generated hydrogen based on the dehydrogenation of alcs. was introduced.
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      .
      (c) Sawama, Y.; Nakano, A.; Matsuda, T.; Kawajiri, T.; Yamada, T.; Sajiki, H. H-D exchange deuteration of arenes at room temperature. Org. Process Res. Dev. 2019, 23, 648– 653,  DOI: 10.1021/acs.oprd.8b00383
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      13c
      H-D Exchange Deuteration of Arenes at Room Temperature
      Sawama, Yoshinari; Nakano, Akihiro; Matsuda, Takumi; Kawajiri, Takahiro; Yamada, Tsuyoshi; Sajiki, Hironao
      Organic Process Research & Development (2019), 23 (4), 648-653CODEN: OPRDFK; ISSN:1083-6160. (American Chemical Society)
      Arenes underwent C-H deuteration reactions with D2O in the presence of Pt/C, Ir/C, or combinations of both catalysts in isopropanol/D2O under argon at ambient temp. to yield arenes deuterated at the arene C-H bonds.
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      .
      (d) Yamada, T.; Sawama, Y.; Shibata, K.; Morita, K.; Monguchi, Y.; Sajiki, H. Multiple deuteration of alkanes synergistically-catalyzed by platinum and rhodium on carbon as a mixed catalytic system. RSC Adv. 2015, 5, 13727– 13732,  DOI: 10.1039/C4RA16386A
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      13d
      Multiple deuteration of alkanes synergistically-catalyzed by platinum and rhodium on carbon as a mixed catalytic system
      Yamada, Tsuyoshi; Sawama, Yoshinari; Shibata, Kyoshiro; Morita, Kosuke; Monguchi, Yasunari; Sajiki, Hironao
      RSC Advances (2015), 5 (18), 13727-13732CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
      An efficient and mild multiple deuteration method for alkanes catalyzed by the combined use of heterogeneous platinum on carbon (Pt/C) and rhodium on carbon (Rh/C) catalysts in i-PrOD-d8 and D2O as a mixed solvent was developed. The present multi-deuteration was initiated by the transition metal-catalyzed dedeuteration of i-PrOD-d8 to produce D2 and the subsequent C-H bond activation of alkanes catalyzed by the Pt/C and/or Rh/C-D2 complex. This method could be applied to the deuteration of wide variety of linear, branched and cyclic alkanes as useful deuterated materials under mild conditions.
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    14. 14
      Zhang, L.; Zhou, M.; Shao, L.; Wang, W.; Fan, K.; Qin, Q. Reactions of Fe with H2O and FeO with H2. A Combined Matrix Isolation FTIR and Theoretical Study. J. Phys. Chem. A 2001, 105, 6998– 7003,  DOI: 10.1021/jp010914n
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      14
      Reactions of Fe with H2O and FeO with H2. A Combined Matrix Isolation FTIR and Theoretical Study
      Zhang, Luning; Zhou, Mingfei; Shao, Limin; Wang, Wenning; Fan, Kangnian; Qin, Qizong
      Journal of Physical Chemistry A (2001), 105 (29), 6998-7003CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      The study of the reactions of transition metal atoms with water is continued in this work. Here we report the study of the reactions of Fe with H2O and FeO with H2. In agreement with previous thermal atom expts., laser-ablated Fe atoms reacted with H2O to form the FeOH2 and HFeOH mols. as characterized by matrix isolation FTIR spectroscopy. On photolysis, the Fe atoms could further insert into the OH bonds in H2O mols. with a stepwise pattern to form multi metal-oxo core species including HFeOFeH, HFeOFeOH, and possibly HFeOFeOFeH, which were identified by isotopic substitutions and d. functional calcns. Reactions of FeO with H2 also lead to HFeOH as the primary product. In addn., a potential energy surface for the Fe + H2O ↔ FeO + H2 reaction was constructed to elucidate the reaction mechanisms.
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    15. 15
      (a) Peng, B.; Zhao, C.; Mejía-Centeno, I.; Fuentes, G. A.; Jentys, A.; Lercher, J. A. Comparison of kinetics and reaction pathways for hydrodeoxygenation of C3 alcohols on Pt/Al2O3. Catal. Today 2012, 183, 3– 9,  DOI: 10.1016/j.cattod.2011.10.022
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      15a
      Comparison of kinetics and reaction pathways for hydrodeoxygenation of C3 alcohols on Pt/Al2O3
      Peng, Baoxiang; Zhao, Chen; Mejia-Centeno, Isidro; Fuentes, Gustavo A.; Jentys, Andreas; Lercher, Johannes A.
      Catalysis Today (2012), 183 (1), 3-9CODEN: CATTEA; ISSN:0920-5861. (Elsevier B.V.)
      The catalytic hydrodeoxygenation of C3 alcs. (1- and 2-propanol, 1,2- and 1,3-propanediol, and glycerol) on Pt/Al2O3 has been mechanistically explored in the aq. phase. Dehydrogenation on Pt and dehydration on alumina are the main elementary reaction pathways. In water, carbon-carbon bond cleavage for alcs. with terminal hydroxyl groups occurs via decarbonylation of aldehydes (generated by dehydrogenation of alcs.) and decarboxylation of acids, the latter being formed by disproportionation from aldehydes. The presence of water as solvent suppresses the dehydration for mono-alcs. mainly via blocking of Lewis acid sites by water. Dehydration is still the dominating primary reaction for 1,3-propanediol and glycerol, as the higher no. of hydroxyl groups weakens the C-O bond strength. The overall reactivity of C3 alcs. decreases in the order of 1,3-propanediol ≈ glycerol > 1,2-propanediol ≈ 1-propanol.
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      .
      (b) Nakagawa, Y.; Mori, K.; Chen, K.; Amada, Y.; Tamura, M.; Tomishige, K. Hydrogenolysis of CO bond over Re-modified Ir catalyst in alkane solvent. Appl. Catal., A 2013, 468, 418– 425,  DOI: 10.1016/j.apcata.2013.09.021
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      15b
      Hydrogenolysis of CO bond over Re-modified Ir catalyst in alkane solvent
      Nakagawa, Yoshinao; Mori, Kazuma; Chen, Kaiyou; Amada, Yasushi; Tamura, Masazumi; Tomishige, Keiichi
      Applied Catalysis, A: General (2013), 468 (), 418-425CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
      Hydrogenolysis of alcs. was carried out using n-heptane solvent and IrReOx/SiO2 catalyst, which has been known to be active in water solvent. Hydrogenolysis of trans-1,2-cyclohexanediol proceeded more smoothly in n-heptane than in water. The max. yield of cyclohexanol was 74%, and at longer reaction time cyclohexane was selectively formed (>80% yield). Stronger adsorption of substrate on catalyst surface in n-heptane than in water is one of factors in obtaining the good yields. Alkane solvent was also advantageous to water solvent in hydrogenolysis of mono-alcs. The reaction route via acid-catalyzed dehydration and subsequent hydrogenation is enhanced in alkane solvent. On the other hand, the "direct" hydrogenolysis driven by the hydride-like species is suppressed in alkane solvent, leading lower activity in n-heptane for hydrogenolysis of tetrahydrofurfuryl alc. or 1,2-hexanediol, which smoothly react over IrReOx/SiO2 catalyst in water.
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      .
      (c) Zhu, S.; Hao, S.; Zheng, H.; Mo, T.; Li, Y.; Zhu, Y. One-step hydrogenolysis of glycerol to biopropanols over Pt–H4SiW12O40/ZrO2 catalysts. Green Chem. 2012, 14, 2607– 2616,  DOI: 10.1039/c2gc35564g
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      15c
      One-step hydrogenolysis of glycerol to biopropanols over Pt-H4SiW12O40/ZrO2 catalysts
      Zhu, Shanhui; Zhu, Yulei; Hao, Shunli; Zheng, Hongyan; Mo, Tao; Li, Yongwang
      Green Chemistry (2012), 14 (9), 2607-2616CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
      The 1-step hydrogenolysis of biomass-derived glycerol to propanols (1-propanol + isoPrOH), which are known as biopropanols, was studied over different supported Pt-H4SiW12O40 (HSiW) bi-functional catalysts in aq. media. Among the catalysts/supports tested, Pt-HSiW supported over ZrO2 converted glycerol to biopropanols with high selectivity and high yield (94.1%), while exhibiting long-term stability (160 h). This catalyst can be resistant to the impurities present in crude glycerol. The reaction pathway to propanols from glycerol probably proceeds mainly through 1,2-propanediol. With the strategy toward 1-step hydrogenolysis of glycerol to biopropanols sustainably, the biomass can be readily transformed to biodiesel and biopropanols via glycerol, which will bring about the benign development of the biodiesel industry.
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    16. 16
      Arčon, I.; Kolar, J.; Kodre, A.; Hanžel, D.; Strlič, M. XANES analysis of Fe valence in iron gall inks. X-Ray Spectrom. 2007, 36, 199– 205,  DOI: 10.1002/xrs.962
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      16
      XANES analysis of Fe valence in iron gall inks
      Arcon, Iztok; Kolar, Jana; Kodre, Alojz; Hanzel, Darko; Strlic, Matija
      X-Ray Spectrometry (2007), 36 (3), 199-205CODEN: XRSPAX; ISSN:0049-8246. (John Wiley & Sons Ltd.)
      In this study, we investigate the feasibility and reliability of Fe K-edge XANES spectroscopy as a tool in detn. of Fe2+/Fe3+ ratio in historic inks. We have measured Fe K-edge XANES spectra of several historic and model iron gall inks with different Fe2+/Fe3+ ratios, together with some std. ref. Fe2+ and Fe3+ compds. with known local at. structure and symmetry around Fe atoms. We examine different approaches to det. relative amt. of Fe2+ in iron gall inks from the Fe K-edge shifts, and demonstrate that a proper choice of the Fe ref. compds. with similar symmetry, same type of neighbor atoms in nearest coordination shells, arranged in a similar local structure is crucial for the abs. calibration of the Fe K-edge shift and consequently a reliable detn. of Fe2+/Fe3+ ratio in the sample. Best results, with the accuracy of ±2%, are obtained by a linear combination fit with XANES spectrum of FeSO4·7H2O as a ref. for Fe2+ and spectrum of an iron gall ink contg. predominantly Fe3+.
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    17. 17
      Tomita, A.; Shimizu, K.; Kato, K.; Akita, T.; Tai, Y. Mechanism of Low-Temperature CO Oxidation on Pt/Fe-Containing Alumina Catalysts Pretreated with Water. J. Phys. Chem. C 2013, 117, 1268– 1277,  DOI: 10.1021/jp304940f
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      17
      Mechanism of Low-Temperature CO Oxidation on Pt/Fe-Containing Alumina Catalysts Pretreated with Water
      Tomita, Atsuko; Shimizu, Ken-ichi; Kato, Kazuo; Akita, Tomoki; Tai, Yutaka
      Journal of Physical Chemistry C (2013), 117 (3), 1268-1277CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      In a previous article (Catal. Commun. 2012, , 194), we reported that Pt/Fe-contg. alumina catalysts pretreated with water could catalyze CO oxidn. even below room temp. To clarify the effect of the water pretreatment and the reaction mechanism of the novel catalytic system, in situ Fourier transform IR (FT-IR), and X-ray absorption fine structure (XAFS) measurements during CO oxidn. were conducted. From FT-IR measurements, it was revealed that the Pt surface of the catalyst was covered with CO and that the adsorbed CO mols. did not desorb easily, as in the case of conventional Pt/Al2O3 catalyst. Pt LIII XAFS results also suggested the presence of CO on the Pt surface during CO oxidn. Thresholds of Fe K X-ray absorption near-edge structure shifted with the change between oxidative (0.5% O2/He) and reductive (1% CO/He) atmospheres, indicating that the Fe redox change Fe2+ ↔ Fe3+ can participate in the reaction. From the degree of the shifts and av. Pt diams. derived from high-angle annular dark-field scanning transmission electron microscopy and metal dispersion measurements, it was concluded that PtNP/FeOx boundaries were efficiently formed upon the water pretreatment. The enhanced reactivity of the water-pretreated catalyst can be attributed to the increased no. of boundaries and Pt diam.
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    18. 18

      X-ray photoelectron spectroscopy (XPS) analysis of fresh 10% Pt/C indicated that zero valent of platinum was supported on carbon. See Supporting Information.

      There is no corresponding record for this reference.
    19. 19

      Although Pt/C-catalyzed dehydrogenation of 9 in the absence of 8 provided 8 as a dehydrogenated product, methylcyclohexane was also produced by the hydrogenation of 9 using H2 in situ-generated via the dehydrogenation process of 8 to 9. See Supporting Information.

      There is no corresponding record for this reference.
    20. 20
      (a) Birch, A. J. Reduction by Dissolving Metals. J. Chem. Soc. 1944, 430– 436,  DOI: 10.1039/jr9440000430
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      20a
      Reduction by dissolving metals. I
      Birch, Arthur J.
      Journal of the Chemical Society (1944), (), 430-6CODEN: JCSOA9; ISSN:0368-1769.
      Since Na in liq. NH3 behaves as a soln. of metal cations and solvated electrons in equil. with metal atoms, it might be expected to reduce by "electron addn." but the addn. of a ready proton source (such as an alc.) to the reagent renders redn. by nascent H a possibility. The action of Na in liq. NH3 on a no. of C10H8 and C6H6 derivs. in the presence and in the absence of an alc. has been studied to det. whether the presence of the latter alters the course of the reaction. 1-C10H7OH (I) (5.5 g.) and 1.5 g. of NaNH2 in 60 cc. liq. NH3, treated with 1.8 g. Na during 1 h., give 0.3 g. of the 5,8-dihydro deriv. (II); without NaNH2 but with 2.9 g. tert-AmOH, the yield of II was 3.2 g. (65%); 10 g. I and 2.7 g. NaNH2 in 110 cc. NH3, treated with 12.5 g. tert-AmOH and 3.2 g. Na, give about 9 g. of II. Under the 3 above conditions, 2-C10H7OH gives (1) a trace of the 5,8-dihydro deriv. and β-tetralone, (2) 65% and (3) 50% of the tetralone. Treatment of the alk. soln. from (1) with Me2SO4 gives mainly ar-dihydro-2-methoxynaphthalene, b14 145-50°. 1-C10H7CO2H with NaNH2 and Na in NH3 gives the 1,4-dihydro deriv., m. 75°; heating with 20% NaOH at 100° for 30 min. gives the 3,4-dihydro deriv., m. 112°. MeO derivs. of C6H6 and its homologs give about 10% of the phenol (through demethylation) and a mixt. of the starting material and redn. product which were difficult to sep.; the presence of the dihydro deriv. was proved by treatment with hot dil. mineral acid, the product being α,β-unsatd. ketones. PhOMe gave 20% of 2-cyclohexen-1-one (III). 2-MeC6H4OMe gave 12% of the 6-Me deriv. of III (2,4-dinitrophenylhydrazone, bright orange, m. 122-6°). 3-MeC6H4OMe (20 g.) in 28 g. MeOH, added during 1 h. to 20 g. Na in 500 cc. liq. NH3, gave 2 fractions: one b. 105-20° (contg. 1-methyl-cyclohexene, identified as the nitrosochloride, m. 92-3°); the other b. 165-73° and contained essentially 3-methyl-2,5-dihydroanisole (IV); it showed no light absorption in the region 2400-2800 A. IV, refluxed with 10% aq. H2SO4 for 1 h. and treated with H2NNHCONH2, gives 3-methyl-2-cyclohexen-1-one semicarbazidosemicarbazone, m. 210° (decompn.), insol. in boiling EtOH, and the semicarbazone, m. 199-200°; 2,4-dinitrophenylhydrazone, dark red, m. 173°. 4-MeOC6H4Me gives 33% of the 4-Me deriv. of III. 2,6-Me2C6H3OMe gives 10% of the 2,6-di-Me deriv. of III; semicarbazone, cream, m. 210-11°; 2,4-dinitrophenylhydrazone, red, m. 153°. 2,5-Me2C6H3OMe gives 15% of the 3,6(?)-di-Me deriv. of III, whose semicarbazidosemicarbazone, m. 214° (decompn.) (no semicarbazone is formed); 2,4-dinitrophenylhydrazone, orange-red, m. 134°. 2,4-Me2C6H3OMe gives 22% of the 4,6-di-Me deriv. of III; semicarbazone, cream, m. 175°; 2,4-dinitrophenylhydrazone, red, m. 152°. 3,4-Me2C6H3OMe gives 35% of the 3,4(?)-di-Me deriv. of III; semicarbazone, cream, m. 193°; 2,4-dinitrophenylhydrazone, red, m. 146°. 3,5-Me2C6H3OMe gives 16% of the 3,5-di-Me deriv. of III; semicarbazidosemicarbazone(?), m. 199° (decompn.). 5-Methoxy-1,2,3,4-tetrahydronaphthalene gave a trace of 1-keto-Δ9,10-octalin but the 6-MeO isomer (V) yields 44% of 2-keto-Δ1,9-octalin; the 5-Me deriv. of V did not give a ketonic product. 5-Methoxyhydrindene gives 30% of 5-keto-4,9-tetrahydrohydrindene; semicarbazone, cream, m. 228-30°; 2,4-dinitrophenylhydrazone, red, m. 197-8°. 5-Methyl-2-isopropylanisole gives a small yield of piperitone. Geranyl Me ether gives geraniolene, b. 165-70°. m-C6H4Me2 (18 g.) and 25 cc. EtOH, added to 10 g. Na in 150 cc. liq. NH3, give 15 g. of an oil b. 142-4° which contains about 21% of benzenoid material (UV spectrum); it yields a nitrosochloride, m. 123° (decompn.), and a nitrolpiperidine, m. 137°, of 2,5-dihydro-m-xylene. The structure was established by ozonolysis, CH2Ac2 being formed. p-C6H4Me2 gives 2,5-(?)-dihydro-p-xylene; this gives a nitrosochloride m. 98° and a nitrolpiperidine, m. 133°. p-Cymene gives a fraction b. 179-80° which contains about 25-30% of a dihydro deriv., consisting partly of γ-terpinene. Tetralin gives an oil, b. 204-8° which contains some 1,2,3,4,5,8-hexahydronaphthalene, whose nitrosochloride, bright blue, m. 91°. If a C6H6 ring bearing MeO and alkyl groups (or the ends of a satd. ring) is written in the Dewar formulas in which the bridge head is not occupied by a MeO group, the chief redn. product will correspond to the formula having the least no. of substituents at the bridge head. 2,3-Disubstituted anisoles give 2 possible formulas between which the rules do not distinguish and the rule is restated as follows: Redn. will tend to be initiated (a) in an unoccupied position and (b) o- or m-rather than p- to an alkyl or MeO group, the latter having the greater deactivating effect in both cases. The mechanism of the nascent H redn. is still in doubt. The practical application of this type of redn. is limited by the low soly. of many compds. in liq. NH3, since redn. is in competition with H evolution.
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      .
      (b) Zimmerman, H. E. A Mechanistic Analysis of the Birch Reduction. Acc. Chem. Res. 2012, 45, 164– 170,  DOI: 10.1021/ar2000698
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      20b
      A Mechanistic Analysis of the Birch Reduction
      Zimmerman, Howard E.
      Accounts of Chemical Research (2012), 45 (2), 164-170CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
      The Birch Redn. is one of the main reactions of org. chem. The reaction involves the reaction of dissolving metals in ammonia with arom. compds. to produce 1,4-cyclohexadienes. Discovered by Arthur Birch in 1944, the reaction occupies 300 pages in Org. Reactions to describe its synthetic versatility. Thus, it is remarkable that the reaction mechanism has been so very controversial and only relatively recently has been firmly established. Perhaps this is not that surprising, since the reaction also has many unusual and esoteric mechanistic facets. Here, I provide a description of how I have applied ever-evolving levels of quantum mechanics and a novel exptl. test to understand details of the mechanism and the origins of the selectivities obsd. in the Birch redn. The reaction involves an initial radical anion resulting from introduction of an electron from the blue liq. ammonia soln. of free electrons formed by the dissoln. of Li or related metals. This radical anion is protonated by an alc. and then further reduced to a carbanion. Finally, the carbanion is protonated using a second proton to afford a nonconjugated cyclohexadiene. The regiochem. depends on substituents present. With 18 resonance structures in the case of anisole radical anion, prediction of the initial protonation site would seem difficult. Nevertheless, computational methods from Huckel theory through modern d. functional calcns. do correctly predict the site of protonation. An esoteric test established this mechanism exptl. The nature of the carbanion also is of mechanistic interest, and the preponderance of the resonance structure shown was revealed from Huckel calcns. involving variable bond orders. For the trianion from benzoic acid, parallel questions about structure are apparent, and have been answered. Some mechanistic questions are answered exptl. and some by modern computations. Recently, our mechanistic understanding has led to a variety of synthetic applications. For example, the prepn. of alkyl aroms. from benzoic acids makes use of the intermediates formed in these reactions. This Account provides an overview of both exptl. techniques and theor. methodol. used to provide detailed mechanistic understanding of the Birch Redn.
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    21. 21
      Le Bailly, B. A. F.; Greenhalgh, M. D.; Thomas, S. P. Iron-catalysed, hydride-mediated reductive cross-coupling of vinyl halides and Grignard reagents. Chem. Commun. 2012, 48, 1580– 1582,  DOI: 10.1039/C1CC14622J
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      21
      Iron-catalysed, hydride-mediated reductive cross-coupling of vinyl halides and Grignard reagents
      Le Bailly, Bryden A. F.; Greenhalgh, Mark D.; Thomas, Stephen P.
      Chemical Communications (Cambridge, United Kingdom) (2012), 48 (10), 1580-1582CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      An iron-catalyzed, hydride-mediated reductive cross-coupling reaction has been developed for the prepn. of alkanes. Using a bench-stable iron(II) pre-catalyst, reductive cross-coupling of vinyl iodides, bromides and chlorides with aryl- and alkyl Grignard reagents successfully gave the products of formal sp3-sp3 cross-coupling reactions.
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    22. 22
      Cai, Y.; Qian, X.; Gosmini, C. Cobalt-Catalyzed Csp3-Csp3 Homocoupling. Adv. Synth. Catal. 2016, 358, 2427– 2430,  DOI: 10.1002/adsc.201600213
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      22
      Cobalt-Catalyzed Csp3-Csp3 Homocoupling
      Cai, Yingxiao; Qian, Xin; Gosmini, Corinne
      Advanced Synthesis & Catalysis (2016), 358 (15), 2427-2430CODEN: ASCAF7; ISSN:1615-4150. (Wiley-VCH Verlag GmbH & Co. KGaA)
      An efficient and easy method for Csp3-Csp3 homocoupling was developed using cobalt bromide as catalyst. A series of functionalized alkyl bromides and alkyl chlorides were coupled in high yields under mild conditions. This reaction seems to involve a radical intermediate.
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    The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.9b01130.

    • XANES, EXAFS, and PNR analysis, XPS of fresh 10% Pd/C, mechanism study, and spectroscopic data of the products (PDF)


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