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Room-Temperature Intermolecular Hydroamination of Vinylarenes Catalyzed by Alkali-Metal Ferrate Complexes
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Cite this: ACS Org. Inorg. Au 2025, 5, 1, 62–68
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https://doi.org/10.1021/acsorginorgau.4c00066
Published November 11, 2024

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Abstract

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Alkene hydroamination of multiple bonds represents a valuable and atom-economical approach to accessing amines, using simple and widely available starting materials. This reaction requires a metal catalyst, and despite the success of noble transition metals, s-block, or f-block elements, iron organometallic complexes have found limited applications. Partnering iron with an alkali metal and switching on bimetallic cooperativity, we report the synthesis and characterization of a series of highly reactive alkali-metal alkyl ferrate complexes, which can deprotonate amines and activate them toward the catalytic hydroamination of vinylarenes. An alkali-metal effect has been observed, with the sodium analogue being the best for an efficient hydroamination of different styrene derivatives and amines. Stoichiometric studies on the reaction of the sodium tris(alkyl) ferrate complex with 3 mol equiv of piperidine evidenced the ability of the three alkyl groups on Fe to undergo amine metalation, furnishing a novel tris(amido) sodium ferrate which is postulated as a key intermediate in these catalytic transformations. The enhanced reactivity of these alkali-metal ferrates contrasts sharply with that of the Fe(II) bis(alkyl) precursor which is completely inert toward alkene hydroamination.

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Introduction

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Amines are cornerstone chemical compounds, found in many natural products, agrochemicals, pharmaceuticals, polymers, or dyes. (1,2) A direct and atom-economical way to prepare these compounds is the hydroamination of multiple carbon–carbon bonds, in which a N–H unit is added into a C–C unsaturated bond, forming a C–H and a C–N bond (Figure 1a). This reaction is very useful to form tertiary amines from readily available starting materials such as alkenes and secondary amines. However, despite being generally thermoneutral or thermodynamically favorable reactions (depending on the substrates used), (3) they usually require a metal catalyst because they are not kinetically favorable (alkenes and amines are both considered electron-rich). (4) For said catalytic activation, different strategies have been reported such as the activation of the π-system via coordination (typical for late transition metals), (5,6) or the activation of the amine moiety via deprotonation to form a nucleophilic metal amide species (typical of s-block metals, lanthanides and actinides). (7)

Figure 1

Figure 1. Hydroamination of unsaturated systems, (a) general hydroamination of alkenes, (b) intermolecular hydroamination with Lewis acid catalysis, (c) intramolecular hydroamination, and (d) intermolecular hydroamination with ferrates (this work).

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Despite the advances in this field, the use of iron-based catalysts for activating amine N–H bonds and promoting catalytic hydroamination reaction is still largely underdeveloped. (8−12) This is somehow surprising considering that Earth-abundant metal catalysis, and in particular using iron compounds, continues to attract widespread interest as a more sustainable alternative to traditional precious metal catalysis, with the added advantages of having lower price, being more environmentally benign and exhibiting generally lower toxicity. (13,14) Regarding iron catalyzed hydroamination of alkenes, iron(III) chloride has been used as Lewis acid activator, promoting the formation of the aminated Markovnikov product (Figure 1b). (15−17) Organometallic complexes of iron have also been shown to activate the N–H amine moiety and promote intramolecular hydroamination reactions. Thus, Hannedouche and co-workers have reported the use of β-diketiminate iron(II) alkyl complexes (Fe1) for catalytic hydroamination of primary amines tethered to alkenes, leading to the formation of 5- and 6-membered ring heterocycles (Figure 1c). (18−20) This methodology is characterized by the formation of an iron(II) amidoalkene via deprotonation of the N–H bond, which after alkene migratory insertion into the iron amido bond forms the desired C–N bond. However, this approach was limited to the intramolecular hydroamination of primary amines with geminal disubstitution, narrowing the applicability of these systems to synthesize amines.
Inspired by this work and with the aim of exploring new ways of amine activation with iron-based complexes, we wondered about the possibility of forming more reactive bimetallic alkali metal/iron ate complexes (ferrates). This strategy has been previously exploited by our group in magnesium-catalyzed alkene hydroamination, showing that while neutral Mg dialkyl complexes are completely inert toward this reaction, using potassium magnesiate as a precatalyst allows for the effective hydroamination of styrene type molecules with a range of amines at room temperature in almost quantitative yields. (21) Within stoichiometric transformations, the alkali-metal magnesiate amido complex could be isolated, showing the deprotonation of the amine motive to form a high order magnesiate, which was proposed as part of the catalytic cycle.
Regarding the use of ferrates in synthesis, they have been proposed and observed as key intermediates in cross-coupling reactions, showing their higher activity to promote these C–C bond formation processes. (22−28) Their use have not been limited to catalysis, and they have been employed as well in stoichiometric transformations, where our group have also demonstrated their higher reactivity toward deprotonative metalation. (29−33) For example, we could show that NaFe(HMDS)3, HMDS = 1,1,1,3,3,3-hezamethyldisilazide, is able to metalate fragile fluoroarenes in high yields, it being remarkable that the monometallic counterparts Fe(HMDS)2 and NaHMDS cannot deliver the metalated intermediates in an efficient manner. However, their low nucleophilicity made us consider a different approach to access bimetallic iron complexes with less bulky and more nucleophilic amines such a piperidine. We envisioned that alkali metal trialkyl ferrate complexes would be basic enough to form in situ the corresponding alkali metal amide ferrates, which in turn could be able to catalyze the hydroamination of styrene type molecules and give the anti-Markovnikov aminated product (Figure 1d). Furthermore, the presence of an alkali-metal can also contribute to the activation of the olefin acting as a built-in Lewis acid, (34,35) while the iron center would increase the stability of the reaction intermediates, forming less polar Fe–N (or Fe–C) bonds, avoiding side reactions such as polymerization.

Results and Discussion

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For the synthesis of bimetallic trialkyl iron(II) complexes, the –CH2SiMe3 group was chosen due to its higher steric bulk and the absence of β-hydrogens, limiting the possible decomposition pathways. A few examples of alkyl and aryl iron(II) and (III) ate complexes have been isolated and characterized recently, mostly in the context of cross-coupling reactions with organolithium or Grignard reagents, being prepared from adding an excess of organometallic reagent into an iron salt precursor. (22−28) In our case, we opted instead for a cocomplexation approach, since we predicted that the organometallic compounds would have better solubility and stability in apolar hydrocarbon solvents. Starting from (TMEDA)Fe(CH2SiMe3)2 (36,37) we added an equivalent of the corresponding AMCH2SiMe3 (AM = Li, Na, K) and the Lewis donor TMEDA (N,N,N′,N′-tetramethylethylenediamine) or PMDETA (N,N,N′,N″,N″-pentamethyldiethylenetriamine) in hexane to obtain the corresponding bimetallic iron–ate complexes in moderate to good yields (Figures 2a and S9). In the case of the lithium analogue, the tridentate donor PMDETA was optimal to complete the coordination sphere, whereas with the bigger sodium and potassium analogues, two equiv of TMEDA completed the coordination of the alkali metal cations. The corresponding iron complexes FeLi, FeNa, and FeK could be isolated as off-white crystalline solids in 85%, 74%, and 35% yield, respectively. We observed partial decomposition of the potassium analogue during their synthesis due to the high reactivity of the heavier alkali metal alkyl reagents, explaining the lower yield obtained. Saturated solutions of the compounds in hexane were stored at −30 °C for 16 h to give single crystals suitable for X-ray crystallography, showing very similar trialkyl iron(II) units with Fe–C average distances of 2.087, 2.082, and 2.083 Å for FeLi, FeNa, and FeK, respectively. The alkali metal in these complexes shows contact with the carbon atom(s) of the trialkyl iron unit, where the lithium analogue forms a contacted ion-pair with one of the –CH2SiMe3 groups with a Li–C distance of 2.400 Å, whereas the sodium and potassium ferrates form a ring-closed contacted ion pair motif, with contact with two –CH2SiMe3 groups in an average AM–C distance of 3.102 Å (AM = Na) and 3.227 Å (AM = K). Similar contacted ion pair motifs are found in Zn, Mg, or Mn-ate complexes, where (PMDETA)LiM (CH2SiMe3)3 (M = Zn, Mg) shows a single contact with an alkyl group, whereas (TMEDA)2AMM(CH2SiMe3)3 (AM = Na, K; M = Zn, Mn) show two contacts with different alkyl groups. (38−40) Solution NMR characterization in deuterated benzene showed, in every case, very similar chemical shifts for the -SiMe3 groups in the 1H NMR spectra around 5 ppm (see Supporting Information for details). The determination of the magnetic moment with the Evans method suggests that they are all high spin Fe(II) centers, with solution effective magnetic moments of 5.46, 5.71, and 5.38 μB for FeLi, FeNa, and FeK, respectively, similar to the magnetic moment of 5.7 μB reported for [Fe(II)Bn3]−. (23)

Figure 2

Figure 2. Bimetallic iron complexes in alkene hydroamination. (a) Synthesis of alkali metal trialkyl ferrates, ellipsoids are displayed at 50% probability, and all H atoms have been omitted for clarity. (b) Styrene hydroamination catalyzed by iron organometallic complexes. Conditions: styrene (0.2 mmol), piperidine (0.25 mmol), catalyst (0.02 mmol), and toluene (0.5 mL). Yields were measured by 1H NMR spectroscopy using hexamethylbenzene as the internal standard.

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With these complexes in hand, we proceeded to test their catalytic activity in hydroamination reactions choosing styrene and piperidine as model substrates due to their known reactivity using alkali metals, alkaline-earth metals, or lanthanide-based catalysts. (41−47) Gratifyingly, the iron ferrates showed excellent catalytic activities when used in 10 mol % loading and using toluene as a solvent at room temperature. Revealing a marked alkali-metal effect, FeLi and FeNa yielded the best results, with the latter being slightly more active and reaching full conversion after 16 h. FeK delivered lower yields of the hydroaminated product with relatively high conversions of styrene, hinting that other decomposition pathways were operating. For comparison, the bimetallic NaFe(HMDS)3 was also tested, but it showed no catalytic activity, presumably due to the higher steric demand of the HMDS units and an incomplete transamidation. (48) The monometallic precursors were also tested in this conditions, showing that (TMEDA)Fe(CH2SiMe3)2 (FeR2) was not active for the hydroamination of styrene and that NaCH2SiMe3 catalyzed this transformation, (49) but the yield obtained was lower with full conversion of the styrene starting material, suggesting that this more reactive catalyst produced a higher amount of side products under this reaction conditions. Moving to more coordinating solvents such as THF slightly slowed down the reaction, but a yield of 94% was obtained when the reaction was heated to 50 °C for 16 h (see Supporting Information for further details).
To try to identify the intermediate species in the hydroamination reaction, we performed stoichiometric experiments of the bimetallic complex FeNa with piperidine in a mixture of hexane/toluene as the solvent. It showed a fast reaction that upon cooling to −30 °C delivered deep red crystals. X-ray diffraction analysis of the crystalline solid revealed the formation of a tetranuclear complex [(TMEDA)NaFe(C5H10N)3]2 (I) formed by two iron and two sodium centers, connected by six piperidide fragments (Figure 3). Adopting a slightly bent Na···Fe···Fe···Na disposition with an average Na···Fe···Fe angle of 164°, each Na atom is chelated by a TMEDA molecule, whereas the Fe centers exhibit distorted tetrahedral geometries coordinating to four piperidide groups. This complex can be envisaged as the piperidide analogue of FeNa, where now the lower steric demand of the amide substituents favors dimerization to form this tetrametallic complex in the solid state, reminiscent of the magnesium analogue. (21) However, the two metallic centers in this complexes are relatively closer than in the magnesium case, dFe–Fe = 2.8739(3) Å and dMg–Mg = 2.9764(8) Å, which could indicate that the transition metal character of iron allows some orbital interaction, as similar Fe–Fe distances have been reported for other iron dimers. (50,51) In solution, an effective magnetic moment of 5.45 μB might suggest that the tetrameric unit breaks to form isolated bimetallic sodium ferrate moieties with a high spin Fe(II) center. When used as catalyst of the hydroamination reaction of styrene with piperidine, we observe a comparable yield of 93% of 1a after 16 h at room temperature, and therefore, we posit that the formation of this trisamido sodium ferrate in solution occurs rapidly and these species are part of the catalytic cycle. We propose that in solution, the trisamido sodium ferrate is able to insert the vinylarene and form an alkyl iron intermediate, which can be protonated by another molecule of amine to close the catalytic cycle. This was further supported by a crossover experiment, in which styrene was reacted with morpholine using I (10 mol %) as catalyst, obtaining 14% of 1a and 78% of 1g (see Supporting Information for details), which further supports the involvement of the bimetallic sodium ferrates in the hydroamination reaction and not the monometallic sodium amides. To test the important role of the alkali metal, when 15-crown-5 was added to the catalytic reaction, a reduced yield of 23% of the corresponding hydroaminated product was obtained, which together with the alkali metal effect reported before confirms the importance of the alkali-metal for an efficient hydroamination.

Figure 3

Figure 3. Synthesis and crystal structure of [(TMEDA)NaFe(C5H10N)3]2 (I) and the proposed catalytic cycle. In the molecular structure, ellipsoids are displayed at 50% probability, and all H atoms have been omitted for clarity.

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With this information in hand, we tested the substrate scope of the reaction (Figure 4). Different styrene type molecules were used, observing good to excellent yields of hydroaminated product with a phenyl (1b), a tert-butyl (1c), or a methyl substituent (1d) in the aromatic ring. Other more sensitive groups such as fluorines were tolerated, albeit the hydroaminated product (1e) was obtained with a low yield. Substitution in the double bond with another phenyl group delivered the corresponding hydroaminated product (1f) in 74% yield. Moving to other amines, we observed that morpholine and N-methylpiperazine could be used instead of piperidine to obtain the hydroaminated products in excellent yields (1g, 1h). However, in this case, the reaction had to be performed using THF as solvent at 50 °C due to the high insolubility of the intermediate species in toluene. Noncyclic amines such as dibenzylamine delivered as well the hydroaminated product (1i) in good yields, showing that the system is not restricted to cyclic amines. Less nucleophilic amines such as N-methylaniline or diphenylamine failed to deliver the hydroamination of styrene, even when heated to higher reaction temperatures, presumably due to their lower nucleophilicity. From the alkene substrate scope, this protocol also remains limited to activated olefins, observing no hydroaminated product when terminal unactivated olefins (i.e., 1-octene) or alkynes (i.e., diphenylacetylene) were reacted at 80 °C for 16 h.

Figure 4

Figure 4. Hydroamination of styrene derivatives with secondary amines. Conditions: vinylarene (0.2 mmol), amine (0.25 mmol), FeNa (0.02 mmol), toluene (0.5 mL), rt, 16 h. (a) Reaction performed at 50 °C, (b) reaction performed in THF, and (c) NMR yield using C6Me6 as the internal standard.

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Conclusions

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Overall, the synthesis and characterization of alkali metal ferrates with alkyl substituents have allowed the development of a new intermolecular hydroamination protocol of styrenes with secondary amines. The more basic alkyl substituents on iron have been able to deprotonate the amine motive, a compound that we have been able to isolate and characterize by X-ray crystallography and NMR spectroscopy when using piperidine. In catalysis, a marked alkali-metal effect can be observed, highlighting the importance of the partnership of both metals. The sodium ferrate showed the best results, whereas the lithium analogue delivered lower rates and the potassium ferrate promoted other unproductive pathways. It is remarkable that the combination of both metals was necessary to obtain high yields of the product, since the dialkyl iron complex did not promote the reaction and the very reactive alkyl sodium formed a higher amount of side products. The hydroamination protocol could be extended to other styrene derivatives and secondary amines, showing the possibilities of this new approach for the synthesis of tertiary amines and broadening the catalogue of iron catalyzed transformations. The partnership of iron with other abundant metals such as alkali metals can open new reactive pathways, showing that this strategy is not limited to the main group elements and can be extended to transition metals.

Experimental Section

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General

All procedures were conducted using standard Schlenk line and glovebox techniques under an inert atmosphere of argon. Hexane was degassed, purified, and collected via an MBraun SPS 5 and stored over 4 Å molecular sieves for at least 24 h prior to use. THF was dried by heating to reflux over sodium wire/benzophenone ketyl radical and stored over 4 Å molecular sieves for 24 h prior to use. Deuterated solvents (C6D6 and C7D8) were purchased from Sigma-Aldrich or Eurisotope, dried over NaK alloy for 16 h, and then cycled through three rounds of degassing by employing a freeze–pump–thaw method. The deuterated solvents were then collected via vacuum transfer and stored under an argon atmosphere over 4 Å molecular sieves. All substrates employed in this study are commercially available and were used as received (solids) or degassed by freeze–pump–thaw and stored over molecular sieves (liquids).
NMR spectra were recorded on Bruker spectrometers operating at 300, 400, or 500 MHz. Elemental analyses (C, H, and N) were conducted with a Flash 2000 organic elemental analyzer (Thermo Scientific). Samples were prepared in the glovebox under an argon atmosphere and sealed in an airtight container prior to analyses. All results were obtained from the Analytical Research and Services Schürch Group of the University of Bern. Samples were weighed on a Mettler Toledo balance with ±2 μg resolution, and sample weights from 1 to 3 mg were used. For calibration, a reference material such as cysteine was used. The presented values are the average of determinations in triplicate to ensure consistency.

Synthesis of Alkali-Metal Ferrates

(PMDETA)LiFe(CH2SiMe3)3 (FeLi)

(TMEDA)Fe(CH2SiMe3)2 (1 mmol, 346.5 mg) and LiCH2SiMe3 (1 mmol, 94.2 mg) were dissolved in 10 mL of hexane. After a few seconds, it formed a light-yellow oil, to which PMDETA (2 mmol, 0.42 mL) was added, and the solvent reduced to a third of the original volume. The mixture was cooled to −30 °C in a bath to form a light brown solid. The supernatant was removed with a syringe, and the solid was washed twice with 3 mL of cold hexane. The resulting solid was dried under a vacuum to obtain a light brown solid (423.4 mg, 85% yield). 1H NMR (300 MHz, C6D6): δ 5.93–3.48 (m, 27H), −0.30 – −10.19 (m, 23H), 7Li NMR (117 MHz, C6D6): δ 4.48. Elemental analysis: Anal. Calcd for C21H56FeLiN3Si3: C, 50.68; H, 11.34; N, 8.44; Found: C, 50.86; H, 11.65; N, 8.86.

(TMEDA)2NaFe(CH2SiMe3)3 (FeNa)

(TMEDA)Fe(CH2SiMe3)2 (2 mmol, 693 mg), NaCH2SiMe3 (2 mmol, 220.4 mg), and TMEDA (2 mmol, 0.300 mL) were dissolved in 15 mL of hexane at 0 °C. The mixture was stirred for 30 min, and a colorless precipitate formed. The supernatant was removed with a canula filtration, the solid was further washed with cold hexane, and the resulting solid was dried under vacuum. The desired compound was obtained as an off-white solid (851 mg, 74% yield). 1H NMR (300 MHz, C6D6): δ 4.88 (s, 27H), 1.56 – −2.31 (m, 32H). Elemental analysis: Anal. Calcd for C24H63FeN4NaSi3: C, 50.32; H, 11.44; N, 9.78. Found: C, 50.18; H, 11.43; N, 9.93.

(TMEDA)2KFe(CH2SiMe3)3 (FeK)

(TMEDA)Fe(CH2SiMe3)2 (1 mmol, 346.5 mg), KCH2SiMe3 (1 mmol, 126.3 mg), and TMEDA (1 mmol, 0.150 mL) were dissolved in 20 mL of hexane at 0 °C. A black solid was formed, and the supernatant was filtered via canula to remove this solid. After removing around half of the solvent under vacuum, a solid started to form. Further cooling down the mixture to 0 °C delivered a colorless solid. The supernatant was removed via canula filtration, and the solid was washed with cold hexane to deliver a crystalline light brown solid (203 mg, 35% yield). 1H NMR (300 MHz, C6D6): δ 6.36–3.84 (m, 27H), 1.08 – −1.44 (m, 32H). Elemental analysis: Anal. Calcd for C24H63FeN4KSi3: C, 48.94; H, 11.12; N, 9.51. Found: C, 48.74; H, 11.18; N, 9.54.

[(TMEDA)NaFe(C5H10N)3]2 (I)

The complex (TMEDA)2·NaFe(CH2SiMe3)3 (0.2 mmol, 114 mg) was dissolved in 3 mL of toluene in the glovebox. To this solution, piperidine (0.6 mmol, 60 μL) was added dropwise to form a brown/red solution. Addition of 2 mL of hexane and cooling down to −30 °C for 16 h delivered dark red crystals, that were suitable for X-ray crystallography. Removal of the supernatant and washing of the solid with cold pentane rendered a brown solid as the desired product (55.5 mg, 62% yield). 1H NMR (300 MHz, C6D6): δ 31.45–22.18 (m), 16.06–12.10 (m), 1.72–1.07 (m), 1.07–0.71 (m), 0.47 – −0.54 (m). Elemental analysis: Anal. Calcd for C42H92Fe2N10Na2: C, 56.37; H, 10.36; N, 15.65. Found: C, 55.92; H, 10.48; N, 15.32.

Catalytic Hydroamination with Alkali-Metal Ferrates

To a J-young NMR tube or a vial was added the catalyst (0.02 mmol, 10 mol %) in a glovebox, and it was dissolved in toluene (or THF). The amine (0.25 mmol) and the vinylarene (0.2 mmol) were then added, and the reaction was left at room temperature for 16 h. After that time, the reaction vessel was opened to air, diluted with EtOAc, and filtered through silica gel. The organic solvent was removed under reduced pressure to give the crude compounds, which, after purification by column chromatography, delivered the desired hydroaminated products.

Data Availability

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The data underlying this study are available in the published article and its Supporting Information.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsorginorgau.4c00066.

  • Experimental details, NMR spectra, and X-ray crystallog-raphy data General methods, synthesis of organometallic complexes, X-ray crystallographic data, stoichiometric reaction with NaFe(HMDS)3, catalytic reactions, cross-over experiment with I and morpholine, characterization of the products, and copies of NMR Spectra (PDF)

Accession Codes

Deposition Numbers 2376520–2376523 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via the joint Cambridge Crystallographic Data Centre (CCDC) and Fachinformationszentrum Karlsruhe Access Structures service.Accession Codes CCDC 2376520–2376523 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

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  • Corresponding Author
  • Author
  • Author Contributions

    CRediT: Andreu Tortajada conceptualization, investigation, methodology, writing - original draft; Eva Hevia conceptualization, funding acquisition, supervision, writing - review & editing.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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We thank the University of Bern and the Swiss National Science Foundation (SNSF) (projects numbers 210608, 200021, and 219318) for its generous sponsorship, which includes the award of a SNSF Swiss Postdoctoral Fellowship to A.T., and the X-ray crystal structure service at the University of Bern for measuring, solving, refining, and summarizing the structure of compounds I, FeLi, FeNa and FeK.

References

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This article references 51 other publications.

  1. 1
    (a) Methodologies in Amine Synthesis: Challenges and Applications; Ricci, A., Ed.; Wiley: Hoboken, NJ, 2021.
    Google Scholar
    There is no corresponding record for this reference.
  2. 2
    Lawrence, S. A. Amines: Synthesis, Properties, and Applications; Cambridge University Press: Cambridge, 2004.
    Google Scholar
    There is no corresponding record for this reference.
  3. 3
    Johns, A. M.; Sakai, N.; Ridder, A.; Hartwig, J. F. Direct Measurement of the Thermodynamics of Vinylarene Hydroamination. J. Am. Chem. Soc. 2006, 128 (29), 9306– 9307,  DOI: 10.1021/ja062773e
    Google Scholar
    3
    Direct Measurement of the Thermodynamics of Vinylarene Hydroamination
    Johns, Adam M.; Sakai, Norio; Ridder, Andre; Hartwig, John F.
    Journal of the American Chemical Society (2006), 128 (29), 9306-9307CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The thermodn. for intermol. hydroamination of vinylarenes with arylamines were measured directly by conducting the addn. processes, as well as cleavage of the addn. products, under conditions in which amine, vinylarene, and phenethylamine are all present. The reaction of N-methylaniline with styrene is exothermic by ∼10 kcal/mol but nearly thermoneutral in free energy. The free energies for addns. of various primary arylamines to styrene and for addns. of primary arylamines to indene, dihydronaphthalene, and two vinylarenes range from 1.3 to -3.5 kcal/mol (K = 0.16-155 M-1). The steric properties of the nucleophile significantly influenced the equil. const. for addn., but the electronic properties of the nucleophile had a minor effect on this equil. const. These measurements led to the first successful intermol. addn. of aniline to indene and 1,2-dihydronaphthalene and shed light on factors requiring consideration when choosing substrates and reaction conditions for this transformation.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XmtVShs74%253D&md5=c9b6a68e28b5969f271590564b6b7db2
  4. 4
    Müller, T. E.; Hultzsch, K. C.; Yus, M.; Foubelo, F.; Tada, M. Hydroamination: Direct Addition of Amines to Alkenes and Alkynes. Chem. Rev. 2008, 108 (9), 3795– 3892,  DOI: 10.1021/cr0306788
    Google Scholar
    4
    Hydroamination: Direct Addition of Amines to Alkenes and Alkynes
    Mueller, Thomas E.; Hultzsch, Kai C.; Yus, Miguel; Foubelo, Francisco; Tada, Mizuki
    Chemical Reviews (Washington, DC, United States) (2008), 108 (9), 3795-3892CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. Hydroamination via direct addn. of amines to alkenes and alkynes was reviewed.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtVCnu7nI&md5=b80417785b6db24cb52835016ef4163d
  5. 5
    Huang, L.; Arndt, M.; Gooßen, K.; Heydt, H.; Gooßen, L. J. Late Transition Metal-Catalyzed Hydroamination and Hydroamidation. Chem. Rev. 2015, 115 (7), 2596– 2697,  DOI: 10.1021/cr300389u
    Google Scholar
    5
    Late Transition Metal-Catalyzed Hydroamination and Hydroamidation
    Huang, Liangbin; Arndt, Matthias; Goossen, Kaethe; Heydt, Heinrich; Goossen, Lukas J.
    Chemical Reviews (Washington, DC, United States) (2015), 115 (7), 2596-2697CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. This review examines recent developments in late transition metal-catalyzed hydroamination and -amidation reactions. In this review, usage of the term hydroamidation is not limited to the substrate classes of amides, sulfonamides, and phosphonamides, but extended to structurally related compds. with a similar pKa range and reactivity, such as carbamates, lactams, ureas, amidines, guanidines, etc.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXjsFChurY%253D&md5=52c63d6ba025e1973c8fec49a9868e31
  6. 6
    Trowbridge, A.; Walton, S. M.; Gaunt, M. J. New Strategies for the Transition-Metal Catalyzed Synthesis of Aliphatic Amines. Chem. Rev. 2020, 120 (5), 2613– 2692,  DOI: 10.1021/acs.chemrev.9b00462
    Google Scholar
    6
    New Strategies for the Transition-Metal Catalyzed Synthesis of Aliphatic Amines
    Trowbridge, Aaron; Walton, Scarlett M.; Gaunt, Matthew J.
    Chemical Reviews (Washington, DC, United States) (2020), 120 (5), 2613-2692CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. In light of the ever-increasing importance of aliph. amines across the range of chem. sciences, this review aims to provide a concise overview of modern transition-metal catalyzed approaches to alkylamine synthesis and their functionalization. Selected examples of amine bond forming reactions include, hydroamination and hydroaminoalkylation, transition-metal catalyzed C(sp3)-H functionalization and transition-metal catalyzed visible-light-mediated light photoredox catalysis.
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  7. 7
    Escorihuela, J.; Lledós, A.; Ujaque, G. Anti-Markovnikov Intermolecular Hydroamination of Alkenes and Alkynes: A Mechanistic View. Chem. Rev. 2023, 123 (15), 9139– 9203,  DOI: 10.1021/acs.chemrev.2c00482
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    There is no corresponding record for this reference.
  8. 8
    Gui, J.; Pan, C.-M.; Jin, Y.; Qin, T.; Lo, J. C.; Lee, B. J.; Spergel, S. H.; Mertzman, M. E.; Pitts, W. J.; La Cruz, T. E.; Schmidt, M. A.; Darvatkar, N.; Natarajan, S. R.; Baran, P. S. Practical Olefin Hydroamination with Nitroarenes. Science 2015, 348 (6237), 886– 891,  DOI: 10.1126/science.aab0245
    Google Scholar
    8
    Practical olefin hydroamination with nitroarenes
    Gui, Jinghan; Pan, Chung-Mao; Jin, Ying; Qin, Tian; Lo, Julian C.; Lee, Bryan J.; Spergel, Steven H.; Mertzman, Michael E.; Pitts, William J.; La Cruz, Thomas E.; Schmidt, Michael A.; Darvatkar, Nitin; Natarajan, Swaminathan R.; Baran, Phil S.
    Science (Washington, DC, United States) (2015), 348 (6237), 886-891CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    The synthesis and functionalization of amines are fundamentally important in a vast range of chem. contexts. We present an amine synthesis that repurposes two simple feedstock building blocks: olefins and nitro(hetero)arenes. Using readily available reactants in an operationally simple procedure, the protocol smoothly yields secondary amines in a formal olefin hydroamination. Because of the presumed radical nature of the process, hindered amines can easily be accessed in a highly chemoselective transformation. A screen of more than 100 substrate combinations showcases tolerance of numerous unprotected functional groups such as alcs., amines, and even boronic acids. This process is orthogonal to other aryl amine syntheses, such as the Buchwald-Hartwig, Ullmann, and classical amine-carbonyl reductive aminations, as it tolerates aryl halides and carbonyl compds.
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  9. 9
    Zhu, K.; Shaver, M. P.; Thomas, S. P. Chemoselective Nitro Reduction and Hydroamination Using a Single Iron Catalyst. Chem. Sci. 2016, 7 (5), 3031– 3035,  DOI: 10.1039/C5SC04471E
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    9
    Chemoselective nitro reduction and hydroamination using a single iron catalyst
    Zhu, Kailong; Shaver, Michael P.; Thomas, Stephen P.
    Chemical Science (2016), 7 (5), 3031-3035CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
    The redn. and reductive addn. (formal hydroamination) of functionalized nitroarenes was reported using a simple and bench-stable iron(III) catalyst and silane. The redn. was chemoselective for nitro groups over an array of reactive functionalities (ketone, ester, amide, nitrile, sulfonyl and aryl halide). The high activity of this earth-abundant metal catalyst also facilitated a follow-on reaction in the reductive addn. of nitroarenes to alkenes, giving efficient formal hydroamination of olefins under mild conditions. Both reactions offered significant improvements in catalytic activity and chemoselectivity and the utility of these catalysts in facilitating two challenging reactions supported an important mechanistic overlap.
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  10. 10
    Zhu, K.; Shaver, M. P.; Thomas, S. P. Amine-Bis(Phenolate) Iron(III)-Catalyzed Formal Hydroamination of Olefins. Chem.─Asian J. 2016, 11 (7), 977– 980,  DOI: 10.1002/asia.201501098
    Google Scholar
    There is no corresponding record for this reference.
  11. 11
    Obradors, C.; Martinez, R. M.; Shenvi, R. A. Ph(i-PrO)SiH2: An Exceptional Reductant for Metal-Catalyzed Hydrogen Atom Transfers. J. Am. Chem. Soc. 2016, 138 (14), 4962– 4971,  DOI: 10.1021/jacs.6b02032
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    11
    Ph(i-PrO)SiH2: An Exceptional Reductant for Metal-Catalyzed Hydrogen Atom Transfers
    Obradors, Carla; Martinez, Ruben M.; Shenvi, Ryan A.
    Journal of the American Chemical Society (2016), 138 (14), 4962-4971CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    We report the discovery of an outstanding reductant for metal-catalyzed radical hydrofunctionalization reactions. Observations of unexpected silane solvolysis distributions in the HAT-initiated hydrogenation of alkenes reveal that phenylsilane is not the kinetically preferred reductant in many of these transformations. Instead, isopropoxy(phenyl)silane forms under the reaction conditions, suggesting that alcs. function as important silane ligands to promote the formation of metal hydrides. Study of its reactivity showed that isopropoxy(phenyl)silane is an exceptionally efficient stoichiometric reductant, and it is now possible to significantly decrease catalyst loadings, lower reaction temps., broaden functional group tolerance, and use diverse, aprotic solvents in iron- and manganese-catalyzed hydrofunctionalizations. As representative examples, we have improved the yields and rates of alkene redn., hydration, hydroamination, and conjugate addn. Discovery of this broadly applicable, chemoselective, and solvent-versatile reagent should allow an easier interface with existing radical reactions. Finally, isotope-labeling expts. rule out the alternative hypothesis of hydrogen atom transfer from a redox-active β-diketonate ligand in the HAT step. Instead, initial HAT from a metal hydride to directly generate a carbon-centered radical appears to be the most reasonable hypothesis.
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  12. 12
    Huehls, C. B.; Lin, A.; Yang, J. Iron-Catalyzed Intermolecular Hydroamination of Styrenes. Org. Lett. 2014, 16 (14), 3620– 3623,  DOI: 10.1021/ol5013907
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    There is no corresponding record for this reference.
  13. 13
    Luescher, M. U.; Gallou, F.; Lipshutz, B. H. The Impact of Earth-Abundant Metals as a Replacement for Pd in Cross Coupling Reactions. Chem. Sci. 2024, 15 (24), 9016– 9025,  DOI: 10.1039/D4SC00482E
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    There is no corresponding record for this reference.
  14. 14
    Bullock, R. M.; Chen, J. G.; Gagliardi, L.; Chirik, P. J.; Farha, O. K.; Hendon, C. H.; Jones, C. W.; Keith, J. A.; Klosin, J.; Minteer, S. D.; Morris, R. H.; Radosevich, A. T.; Rauchfuss, T. B.; Strotman, N. A.; Vojvodic, A.; Ward, T. R.; Yang, J. Y.; Surendranath, Y. Using Nature’s Blueprint to Expand Catalysis with Earth-Abundant Metals. Science 2020, 369 (6505), eabc3183  DOI: 10.1126/science.abc3183
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    There is no corresponding record for this reference.
  15. 15
    Zotto, C. D.; Michaux, J.; Zarate-Ruiz, A.; Gayon, E.; Virieux, D.; Campagne, J.-M.; Terrasson, V.; Pieters, G.; Gaucher, A.; Prim, D. FeCl3-Catalyzed Addition of Nitrogen and 1,3-Dicarbonyl Nucleophiles to Olefins. J. Organomet. Chem. 2011, 696 (1), 296– 304,  DOI: 10.1016/j.jorganchem.2010.09.031
    Google Scholar
    There is no corresponding record for this reference.
  16. 16
    Michaux, J.; Terrasson, V.; Marque, S.; Wehbe, J.; Prim, D.; Campagne, J.-M. Intermolecular FeCl3-Catalyzed Hydroamination of Styrenes. Eur. J. Org Chem. 2007, 2007, 2601– 2603,  DOI: 10.1002/ejoc.200700023
    Google Scholar
    There is no corresponding record for this reference.
  17. 17
    Komeyama, K.; Morimoto, T.; Takaki, K. A. A Simple and Efficient Iron-Catalyzed Intramolecular Hydroamination of Unactivated Olefins. Angew. Chem., Int. Ed. 2006, 45 (18), 2938– 2941,  DOI: 10.1002/anie.200503789
    Google Scholar
    There is no corresponding record for this reference.
  18. 18
    Lepori, C.; Guillot, R.; Hannedouche, J. 1-symmetric β-Diketiminatoiron(II) Complexes for Hydroamination of Primary Alkenylamines. Adv. Synth. Catal. 2019, 361 (4), 714– 719,  DOI: 10.1002/adsc.201801464
    Google Scholar
    There is no corresponding record for this reference.
  19. 19
    Lepori, C.; Bernoud, E.; Guillot, R.; Tobisch, S.; Hannedouche, J. Experimental and Computational Mechanistic Studies of the β-Diketiminatoiron(II)-Catalysed Hydroamination of Primary Aminoalkenes. Chem.─Eur. J. 2019, 25 (3), 835– 844,  DOI: 10.1002/chem.201804681
    Google Scholar
    There is no corresponding record for this reference.
  20. 20
    Bernoud, E.; Oulié, P.; Guillot, R.; Mellah, M.; Hannedouche, J. Well-Defined Four-Coordinate Iron(II) Complexes For Intramolecular Hydroamination of Primary Aliphatic Alkenylamines. Angew. Chem., Int. Ed. 2014, 53 (19), 4930– 4934,  DOI: 10.1002/anie.201402089
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    20
    Well-defined four-coordinate iron(II) complexes for intramolecular hydroamination of primary aliphatic alkenylamines
    Bernoud, Elise; Oulie, Pascal; Guillot, Regis; Mellah, Mohamed; Hannedouche, Jerome
    Angewandte Chemie, International Edition (2014), 53 (19), 4930-4934CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A novel well-defined four-coordinate β-diketiminato iron(II) alkyl complex was shown to be an excellent precatalyst for the highly selective cyclohydroamination of primary aliph. alkenylamines at mild temps. (70-90°). Both empirical kinetic analyses and the reactivity of an isolated iron(II) amido-alkene dimer, [LFe(NHCH2CPh2CH2CH:CH2)]2 [HL = 2,4-bis(2,4,6-trimethylphenylimino)pentane], favor a stepwise σ-insertive mechanism that entails migratory insertion of the pendant alkene into an iron-amido bond assocd. with a rate-detg. aminolysis step.
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  21. 21
    Davin, L.; Hernán-Gómez, A.; McLaughlin, C.; Kennedy, A. R.; McLellan, R.; Hevia, E. Alkali Metal and Stoichiometric Effects in Intermolecular Hydroamination Catalysed by Lithium, Sodium and Potassium Magnesiates. Dalton Trans. 2019, 48 (23), 8122– 8130,  DOI: 10.1039/C9DT00923J
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    21
    Alkali metal and stoichiometric effects in intermolecular hydroamination catalysed by lithium, sodium and potassium magnesiates
    Davin, Laia; Hernan-Gomez, Alberto; McLaughlin, Calum; Kennedy, Alan R.; McLellan, Ross; Hevia, Eva
    Dalton Transactions (2019), 48 (23), 8122-8130CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
    In the presence of lithium, sodium, and potassium alkylmagnesium compds. such as [(PMDETA)2K2Mg(CH2SiMe3)4] (I), diphenylacetylene and styrene underwent regioselective and stereoselective hydroamination reactions with cyclic amines such as piperidine at ambient temp. to yield enamines and amines; the effect of counterion and the order of the magnesium reagent on the hydroamination reactions was studied. The high reactivity of bimetallic alkylmagnesium compds. as hydroamination catalysts contrasts with the complete lack of catalytic ability of neutral Mg(CH2SiMe3)2. The alkali metal (Li, Na, or K) of the bimetallic alkylmagnesium compd. strongly affects its ability to act as a catalyst, indicating that the alkali metal counterion is not a spectator. Potential intermediates were identified, and their crystal structures detd. in some cases. The enhanced catalytic activity of I is rationalized by the higher nucleophilicity of the dianion magnesiates formed in situ during hydroamination and by the ability of potassium ion to engage in π-interactions with the alkyne or alkene and thus to enhance its susceptibility towards nucleophilic attack by amide anions.
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  22. 22
    Sears, J. D.; Muñoz, S. B., III; Daifuku, S. L.; Shaps, A. A.; Carpenter, S. H.; Brennessel, W. W.; Neidig, M. L. The Effect of β-Hydrogen Atoms on Iron Speciation in Cross-Couplings with Simple Iron Salts and Alkyl Grignard Reagents. Angew. Chem., Int. Ed. 2019, 58 (9), 2769– 2773,  DOI: 10.1002/anie.201813578
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    22
    The Effect of β-Hydrogen Atoms on Iron Speciation in Cross-Couplings with Simple Iron Salts and Alkyl Grignard Reagents
    Sears, Jeffrey D.; Munoz, Salvador B., III; Daifuku, Stephanie L.; Shaps, Ari A.; Carpenter, Stephanie H.; Brennessel, William W.; Neidig, Michael L.
    Angewandte Chemie, International Edition (2019), 58 (9), 2769-2773CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The effects of β-H-contg. alkyl Grignard reagents in simple ferric salt cross-couplings were elucidated. The reaction of FeCl3 with EtMgBr in THF gives the cluster species [Fe8Et12]2-, a rare example of a structurally characterized metal complex with bridging Et ligands. Analogous reactions in the presence of NMP, a key additive for effective cross-coupling with simple ferric salts and β-H-contg. alkyl nucleophiles, gave [FeEt3]-. Reactivity studies demonstrate the effectiveness of [FeEt3]- in rapidly and selectively forming the cross-coupled product upon reaction with electrophiles. The identification of Fe-ate species with EtMgBr analogous to those previously obsd. with MeMgBr is a crit. insight, indicating that analogous Fe species can be operative in catalysis for these two classes of alkyl nucleophiles.
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  23. 23
    Bedford, R. B.; Brenner, P. B.; Carter, E.; Cogswell, P. M.; Haddow, M. F.; Harvey, J. N.; Murphy, D. M.; Nunn, J.; Woodall, C. H. TMEDA in Iron-Catalyzed Kumada Coupling: Amine Adduct versus Homoleptic “Ate” Complex Formation. Angew. Chem., Int. Ed. 2014, 53 (7), 1804– 1808,  DOI: 10.1002/anie.201308395
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    23
    TMEDA in Iron-Catalyzed Kumada Coupling: Amine Adduct versus Homoleptic "ate" Complex Formation
    Bedford, Robin B.; Brenner, Peter B.; Carter, Emma; Cogswell, Paul M.; Haddow, Mairi F.; Harvey, Jeremy N.; Murphy, Damien M.; Nunn, Joshua; Woodall, Christopher H.
    Angewandte Chemie, International Edition (2014), 53 (7), 1804-1808CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The reactions of Fe chlorides with mesityl Grignard reagents and tetramethylethylenediamine (TMEDA) under catalytically relevant conditions tend to yield the homoleptic ate complex [Fe(mes)3]- (mes = mesityl) rather than adducts of the diamine, and it is this ate complex that accounts for the catalytic activity. Both [Fe(mes)3]- and the related complex [Fe(Bn)3]- (Bn = benzyl) react faster with representative electrophiles than the equiv. neutral [FeR2(TMEDA)] complexes. Fe(I) species are obsd. under catalytically relevant conditions with both benzyl and smaller aryl Grignard reagents. The x-ray structures of [Fe(Bn)3]- and [Fe(Bn)4]- were detd.; [Fe(Bn)4]- is the 1st homoleptic σ-hydrocarbyl Fe(III) complex that was structurally characterized.
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  24. 24
    Sears, J. D.; Muñoz, S. B., III; Cuenca, M. C. A.; Brennessel, W. W.; Neidig, M. L. Synthesis and Characterization of a Sterically Encumbered Homoleptic Tetraalkyliron(III) Ferrate Complex. Polyhedron 2019, 158, 91– 96,  DOI: 10.1016/j.poly.2018.10.041
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    24
    Synthesis and characterization of a sterically encumbered homoleptic tetraalkyliron(III) ferrate complex
    Sears, Jeffrey D.; Munoz, Salvador B. III; Cuenca, Maria Camila Aguilera; Brennessel, William W.; Neidig, Michael L.
    Polyhedron (2019), 158 (), 91-96CODEN: PLYHDE; ISSN:0277-5387. (Elsevier Ltd.)
    Homoleptic iron-alkyl complexes have been implicated as key intermediates in iron-catalyzed cross-coupling with simple iron salts. Tetraalkyliron(III) ferrate species have been accessible with either Me or benzyl ligands, where the former complex is S = 3/2 and distorted square planar while the latter is a S = 5/2 distorted tetrahedral species. In the current study, a new tetraalkyliron(III) complex is synthesized contg. modified methylene substituents that incorporate large trimethylsilyl (TMS) groups to further probe steric and electronic ligand effects in tetraalkyliron(III) complexes by increasing the electron-donating ability of the ligand while retaining steric bulk. Detailed structural and DFT studies provide insight into electronic structure and bonding of the four-coordinate trimethylsilylmethyl iron(III) complex compared to the previously reported analogs contg. Me and benzyl ligands.
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  25. 25
    Fürstner, A.; Martin, R.; Krause, H.; Seidel, G.; Goddard, R.; Lehmann, C. W. Preparation, Structure, and Reactivity of Nonstabilized Organoiron Compounds. Implications for Iron-Catalyzed Cross Coupling Reactions. J. Am. Chem. Soc. 2008, 130 (27), 8773– 8787,  DOI: 10.1021/ja801466t
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    25
    Preparation, Structure, and Reactivity of Nonstabilized Organoiron Compounds. Implications for Iron-Catalyzed Cross Coupling Reactions
    Fuerstner, Alois; Martin, Ruben; Krause, Helga; Seidel, Gunter; Goddard, Richard; Lehmann, Christian W.
    Journal of the American Chemical Society (2008), 130 (27), 8773-8787CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    A series of unprecedented organoiron complexes of the formal oxidn. states -2, 0, +1, +2, and +3 is presented, which are largely devoid of stabilizing ligands and, in part, also electronically unsatd. (14-, 16-, 17- and 18-electron counts). Specifically, it is shown that nucleophiles unable to undergo β-hydride elimination, such as MeLi, PhLi, or PhMgBr, rapidly reduce Fe(3+) to Fe(2+) and then exhaustively alkylate the metal center. The resulting homoleptic organoferrate complexes [(Me4Fe)(MeLi)][Li(OEt2)]2 (3) and [Ph4Fe][Li(Et2O)2][Li(1,4-dioxane)] (5) could be characterized by x-ray crystal structure anal. However, these exceptionally sensitive compds. turned out to be only moderately nucleophilic, transferring their org. ligands to activated electrophiles only, while being unable to alkylate (hetero)aryl halides unless they are very electron deficient. In striking contrast, Grignard reagents bearing alkyl residues amenable to β-hydride elimination reduce FeXn (n = 2, 3) to clusters of the formal compn. [Fe(MgX)2]n. The behavior of these intermetallic species can be emulated by structurally well-defined lithium ferrate complexes of the type [Fe(C2H4)4][Li(tmeda)]2 (8), [Fe(cod)2][Li(dme)]2 (9), [CpFe(C2H4)2][Li(tmeda)] (7), [CpFe(cod)][Li(dme)] (11), or [Cp*Fe(C2H4)2][Li(tmeda)] (14). Such electron-rich complexes, which are distinguished by short intermetallic Fe-Li bonds, were shown to react with aryl chlorides and allyl halides; the structures and reactivity patterns of the resulting organoiron compds. provide first insights into the elementary steps of low valent iron-catalyzed cross coupling reactions of aryl, alkyl, allyl, benzyl, and propargyl halides with organomagnesium reagents. However, the acquired data suggest that such C-C bond formations can occur, a priori, along different catalytic cycles shuttling between metal centers of the formal oxidn. states Fe(+1)/Fe(+3), Fe(0)/Fe(+2), and Fe(-2)/Fe(0). Since these different manifolds are likely interconnected, an unambiguous decision as to which redox cycle dominates in soln. remains difficult, even though iron complexes of the lowest accessible formal oxidn. states promote the reactions most effectively.
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  26. 26
    Muñoz, S. B., III; Daifuku, S. L.; Sears, J. D.; Baker, T. M.; Carpenter, S. H.; Brennessel, W. W.; Neidig, M. L. The N-Methylpyrrolidone (NMP) Effect in Iron-Catalyzed Cross-Coupling with Simple Ferric Salts and MeMgBr. Angew. Chem., Int. Ed. 2018, 57 (22), 6496– 6500,  DOI: 10.1002/anie.201802087
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    26
    The N-Methylpyrrolidone (NMP) Effect in Iron-Catalyzed Cross-Coupling with Simple Ferric Salts and MeMgBr
    Munoz, Salvador B., III; Daifuku, Stephanie L.; Sears, Jeffrey D.; Baker, Tessa M.; Carpenter, Stephanie H.; Brennessel, William W.; Neidig, Michael L.
    Angewandte Chemie, International Edition (2018), 57 (22), 6496-6500CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The use of N-methylpyrrolidone (NMP) as a co-solvent in ferric salt catalyzed cross-coupling reactions is crucial for achieving the highly selective, preparative scale formation of cross-coupled product in reactions utilizing alkyl Grignard reagents. Despite the crit. importance of NMP, the mol. level effect of NMP on in situ formed and reactive iron species that enables effective catalysis remains undefined. Herein, we report the isolation and characterization of a novel trimethyliron(II) ferrate species, [Mg(NMP)6][FeMe3]2 (1), which forms as the major iron species in situ in reactions of Fe(acac)3 and MeMgBr under catalytically relevant conditions where NMP is employed as a co-solvent. Importantly, combined GC anal. and 57Fe Moessbauer spectroscopic studies identified 1 as a highly reactive iron species for the selective formation generating cross-coupled product. These studies demonstrate that NMP does not directly interact with iron as a ligand in catalysis but, alternatively, interacts with the magnesium cations to preferentially stabilize the formation of 1 over [Fe8Me12]- cluster generation, which occurs in the absence of NMP.
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  27. 27
    Al-Afyouni, M. H.; Fillman, K. L.; Brennessel, W. W.; Neidig, M. L. Isolation and Characterization of a Tetramethyliron(III) Ferrate: An Intermediate in the Reduction Pathway of Ferric Salts with MeMgBr. J. Am. Chem. Soc. 2014, 136 (44), 15457– 15460,  DOI: 10.1021/ja5080757
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    27
    Isolation and Characterization of a Tetramethyliron(III) Ferrate: An Intermediate in the Reduction Pathway of Ferric Salts with MeMgBr
    Al-Afyouni, Malik H.; Fillman, Kathlyn L.; Brennessel, William W.; Neidig, Michael L.
    Journal of the American Chemical Society (2014), 136 (44), 15457-15460CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    While Fe-catalyzed Kumada cross-coupling reactions with simple Fe salts were known since the early 1970s, the nature of the in situ-formed Fe species remains elusive. Herein, the authors report the synthesis of the homoleptic tetralkyliron(III) ferrate complex [MgCl(THF)5][FeMe4] from the reaction of FeCl3 with MeMgBr in THF. Upon warming, this distorted square-planar S = 3/2 species converts to the S = 1/2 species originally obsd. by Kochi and coworkers with concomitant formation of ethane, consistent with its intermediacy in the redn. pathway of FeCl3 to generate the reduced Fe species involved in catalysis.
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  28. 28
    Rousseau, L.; Herrero, C.; Clémancey, M.; Imberdis, A.; Blondin, G.; Lefèvre, G. Evolution of Ate-Organoiron(II) Species towards Lower Oxidation States: Role of the Steric and Electronic Factors. Chem.─Eur. J. 2020, 26 (11), 2417– 2428
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    There is no corresponding record for this reference.
  29. 29
    Maddock, L. C. H.; Borilovic, I.; McIntyre, J.; Kennedy, A. R.; Aromí, G.; Hevia, E. Synthetic, Structural and Magnetic Implications of Introducing 2,2′-Dipyridylamide to Sodium-Ferrate Complexes. Dalton Trans. 2017, 46 (20), 6683– 6691,  DOI: 10.1039/C7DT01319A
    Google Scholar
    29
    Synthetic, structural and magnetic implications of introducing 2,2'-dipyridylamide to sodium-ferrate complexes
    Maddock, Lewis C. H.; Borilovic, Ivana; McIntyre, Jamie; Kennedy, Alan R.; Aromi, Guillem; Hevia, Eva
    Dalton Transactions (2017), 46 (20), 6683-6691CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
    Using a transamination approach to access novel Fe(II) complexes, this study presents the synthesis, x-ray crystallog. and magnetic characterization of new Fe complexes contg. the multifunctional 2,2-dipyridylamide (DPA) ligand using Fe bis(amide) [{Fe(HMDS)2}2] and Na ferrate [{NaFe(HMDS)3}∞] (1) as precursors (HMDS = 1,1,1,3,3,3-hexamethyldisilazide). Reactions of DPA(H) with 1 show exceptionally good stoichiometric control, allowing access to heteroleptic [(THF)2·NaFe(DPA)(HMDS)2] (3) and homoleptic [{THF·NaFe(DPA)3}∞] (4) by using 1 and 3 equiv of DPA(H), resp. Linking this methodol. and co-complexation, which is a more widely used approach to prep. heterobimetallic complexes, 3 can also be prepd. by combining NaHMDS with heteroleptic [{Fe(DPA)(HMDS)}2] (2). In turn, 2 was also synthesized and structurally defined by reacting [{Fe(HMDS)2}2] with two equiv. of DPA(H). Structural studies demonstrate the coordination flexibility of the N-bridged bis(heterocycle) ligand DPA, with 2 and 3 exhibiting discrete monomeric motifs, whereas 4 displays a much more intricate supramol. structure, with one of its DPA ligands coordinating in an anti/anti fashion (as opposed to 2 and 3 where DPA shows a syn/syn conformation), which facilitates propagation of the structure via its central amido N. Magnetic studies confirmed the high-spin electron configuration of the Fe(II) centers in all three compds. and revealed the existence of weak ferromagnetic interactions in dinuclear compd. 2 (J = 1.01 cm-1).
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  30. 30
    Maddock, L. C. H.; Nixon, T.; Kennedy, A. R.; Probert, M. R.; Clegg, W.; Hevia, E. Utilising Sodium-Mediated Ferration for Regioselective Functionalisation of Fluoroarenes via C–H and C–F Bond Activations. Angew. Chem., Int. Ed. 2018, 57 (1), 187– 191,  DOI: 10.1002/anie.201709750
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    30
    Utilising Sodium-Mediated Ferration for Regioselective Functionalisation of Fluoroarenes via C-H and C-F Bond Activations
    Maddock, Lewis C. H.; Nixon, Tracy; Kennedy, Alan R.; Probert, Michael R.; Clegg, William; Hevia, Eva
    Angewandte Chemie, International Edition (2018), 57 (1), 187-191CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Pairing iron bis(amide) Fe(HMDS)2 with Na(HMDS) to form new sodium ferrate base [(dioxane)0.5NaFe(HMDS)3] (1, I) enables regioselective mono and di-ferration (via direct Fe-H exchange) of a wide range of fluoroarom. substrates under mild reaction conditions. Trapping of several ferrated intermediates has provided key insight into how synchronized Na/Fe cooperation operates in these transformations. Furthermore, using excess 1 at 80 °C switches on a remarkable cascade process inducing the collective twofold C-H/threefold C-F bond activations, where each C-H bond is transformed to a C-Fe bond whereas each C-F bond is transformed into a C-N bond.
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  31. 31
    Maddock, L. C. H.; Kennedy, A.; Hevia, E. Lithium-Mediated Ferration of Fluoroarenes. Chimia 2020, 74 (11), 866,  DOI: 10.2533/chimia.2020.866
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    31
    Lithium-mediated ferrationof fluoroarenes
    Maddock, Lewis C. H.; Kennedy, Alan; Hevia, Eva
    Chimia (2020), 74 (11), 866-870CODEN: CHIMAD ISSN:. (Swiss Chemical Society)
    While fluoroaryl fragments are ubiquitous in many pharmaceuticals, the deprotonation of fluoroarenes using organolithium bases constitutes an important challenge in polar organometallic chem. This has been widely attributed to the low stability of the in situ generated aryl lithium intermediates that even at -78 °C can undergo unwanted side reactions. Herein, pairing lithium amide LiHMDS (HMDS = N{SiMe3}2) with FeII(HMDS)2 enables the selective deprotonation at room temp. of pentafluorobenzene and 1,3,5-trifluorobenzene via the mixed-metal base [(dioxane)LiFe(HMDS)3] (1) (dioxane = 1,4-dioxane). Structural elucidation of the organo-metallic intermediates [(dioxane)Li(HMDS)2Fe(ArF)] (ArF = C6F5, 2; 1,3,5-F3-C6H2, 3) prior electrophilic interception demonstrates that these deprotonations are actually ferrations, with Fe occupying the position previously filled by a hydrogen atom. Notwithstanding, the presence of lithium is essential for the reactions to take place as FeII(HMDS)2 on its own is completely inert towards the metalation of these substrates. Interestingly 2 and 3 are thermally stable and they do not undergo benzyne formation via LiF elimination.
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  32. 32
    Maddock, L. C. H.; Mu, M.; Kennedy, A. R.; García-Melchor, M.; Hevia, E. Facilitating the Ferration of Aromatic Substrates through Intramolecular Sodium Mediation. Angew. Chem., Int. Ed. 2021, 60 (28), 15296– 15301,  DOI: 10.1002/anie.202104275
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    There is no corresponding record for this reference.
  33. 33
    Maddock, L. C. H.; Morton, R.; Kennedy, A. R.; Hevia, E. Lateral Metallation and Redistribution Reactions of Sodium Ferrates Containing Bulky 2,6-Diisopropyl-N-(Trimethylsilyl)Anilide Ligands. Chem.─Eur. J. 2021, 27 (61), 15181– 15187,  DOI: 10.1002/chem.202102328
    Google Scholar
    There is no corresponding record for this reference.
  34. 34
    Borys, A. M.; Hevia, E. Exploiting Chemical Cooperativity in Main-Group Bimetallic Catalysis. Trends Chem. 2021, 3 (10), 803– 806,  DOI: 10.1016/j.trechm.2021.07.006
    Google Scholar
    There is no corresponding record for this reference.
  35. 35
    Gil-Negrete, J. M.; Hevia, E. Main Group Bimetallic Partnerships for Cooperative Catalysis. Chem. Sci. 2021, 12 (6), 1982– 1992,  DOI: 10.1039/D0SC05116K
    Google Scholar
    35
    Main group bimetallic partnerships for cooperative catalysis
    Gil-Negrete, Jose M.; Hevia, Eva
    Chemical Science (2021), 12 (6), 1982-1992CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
    A review. Over the past decade s-block metal catalysis has undergone a transformation from being an esoteric curiosity to a well-established and consolidated field towards sustainable synthesis. Earth-abundant metals such as Ca, Mg, and Al have shown eye-opening catalytic performances in key catalytic processes such as hydrosilylation, hydroamination or alkene polymn. In parallel to these studies, s-block mixed-metal reagents have also been attracting widespread interest from scientists. These bimetallic reagents effect many cornerstone org. transformations, often providing enhanced reactivities and better chemo- and regioselectivities than conventional monometallic reagents. Despite a significant no. of synthetic advances to date, most efforts have focused primarily on stoichiometric transformations. Merging these two exciting areas of research, this Perspective Article provides an overview on the emerging concept of s/p-block cooperative catalysis. Showcasing recent contributions from several research groups across the world, the untapped potential that these systems can offer in catalytic transformations is discussed with special emphasis placed on how synergistic effects can operate and the special roles played by each metal in these transformations.
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  36. 36
    Bart, S. C.; Hawrelak, E. J.; Schmisseur, A. K.; Lobkovsky, E.; Chirik, P. J. Synthesis, Reactivity, and Solid State Structures of Four-Coordinate Iron(II) and Manganese(II) Alkyl Complexes. Organometallics 2004, 23 (2), 237– 246,  DOI: 10.1021/om034188h
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    36
    Synthesis, Reactivity, and Solid State Structures of Four-Coordinate Iron(II) and Manganese(II) Alkyl Complexes
    Bart, Suzanne C.; Hawrelak, Eric J.; Schmisseur, Amanda K.; Lobkovsky, Emil; Chirik, Paul J.
    Organometallics (2004), 23 (2), 237-246CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
    Synthesis and characterization of new, four-coordinate, high-spin iron(II) and manganese(II) complexes of the general form L2MR2 (L2 = neutral chelating ligand, R = alkyl) are described. Alkylation of the α-diimine complex, [ArN:C(Me)-C(Me):NAr]FeCl2 (Ar = 2,6-diisopropylphenyl), as well as the enantiopure iron dichloride compds., (-)-(sparteine)FeCl2 and (S)-(tBuBox)FeCl2 ((S)-(tBuBox) = 2,2-bis[2-[4(S)-(R')-1,3-oxazolinyl]propane]), with LiCH2SiMe3 afforded the corresponding dialkyl derivs. Soln. magnetic susceptibility measurements and x-ray diffraction studies reveal each of the new iron(II) bis(trimethylsilylmethyl) complexes to be high-spin, S = 2, tetrahedral mols. In addn. (-)-(sparteine)Fe(CH2CMe3)2, (-)-(sparteine)Fe(CH2C6H5)2, and (S)-(tBuBox)Fe(CH2C6H5)2 were also prepd. and characterized by NMR spectroscopy and elemental anal. An enantiopure, high-spin, tetrahedral manganese(II) dialkyl complex, (-)-(sparteine)Mn(CH2SiMe3)2, has also been synthesized. The catalytic activity of the new iron complexes in carbon-carbon bond forming processes has been evaluated, and stoichiometric reactions of the dialkyls with olefins, carbon monoxide, and the Lewis acid B(C6F5)3 have been examd.
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  37. 37
    Alborés, P.; Carrella, L. M.; Clegg, W.; García-Álvarez, P.; Kennedy, A. R.; Klett, J.; Mulvey, R. E.; Rentschler, E.; Russo, L. Direct C–H Metalation with Chromium(II) and Iron(II): Transition-Metal Host/Benzenediide Guest Magnetic Inverse-Crown Complexes. Angew. Chem., Int. Ed. 2009, 48 (18), 3317– 3321,  DOI: 10.1002/anie.200805566
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    There is no corresponding record for this reference.
  38. 38
    Baillie, S. E.; Clegg, W.; García-Álvarez, P.; Hevia, E.; Kennedy, A. R.; Klett, J.; Russo, L. S. Structural Elucidation, and Diffusion-Ordered NMR Studies of Homoleptic Alkyllithium Magnesiates: Donor-Controlled Structural Variations in Mixed-Metal Chemistry. Organometallics 2012, 31 (14), 5131– 5142
    Google Scholar
    38
    Synthesis, Structural Elucidation, and Diffusion-Ordered NMR Studies of Homoleptic Alkyllithium Magnesiates: Donor-Controlled Structural Variations in Mixed-Metal Chemistry
    Baillie, Sharon E.; Clegg, William; Garcia-Alvarez, Pablo; Hevia, Eva; Kennedy, Alan R.; Klett, Jan; Russo, Luca
    Organometallics (2012), 31 (14), 5131-5142CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
    This paper presents the synthesis and characterization of new homoleptic lithium magnesiate reagents incorporating the silyl-substituted alkyl ligand CH2SiMe3 in the presence of a variety of Lewis base donors, namely THF, 1,4-dioxane, N,N,N',N'-tetramethylethylenediamine (TMEDA), and N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA). The constitution of these bimetallic compds. has been assessed in both the solid state and soln. using a combination of x-ray crystallog. studies and multinuclear NMR spectroscopy, including 1H diffusion-ordered (1H-DOSY) NMR expts. These studies highlight the major role played by the donor mol. in controlling the structure of the complexes as well as the wide structural diversity available for these mixed-metal species ranging from discrete mols., as found for [(PMDETA)LiMg(CH2SiMe3)3] (6), to more complex supramol. arrangements, as in the 1D-polymeric chain [{(THF)LiMg(CH2SiMe3)3}∞] (2) or in the stoichiometrically distinct dioxane solvates [{(dioxane)2LiMgR3}∞] (3) and [{(dioxane)Li2Mg2R6}∞] (4). Furthermore, these studies have also revealed that in some cases the donor mol. can promote a redistribution process, as shown for the reaction of triorganomagnesiate [LiMg(CH2SiMe3)3] (1) with 1 molar equiv. of TMEDA, which led to the formation of lithium-rich tetraorganomagnesiate [(TMEDA)Li2Mg(CH2SiMe3)4] (5) along with Mg(CH2SiMe3)2. The formation of the unprecedented cationic lithium magnesiate [{(PMDETA)2Li2Mg(CH2SiMe3)3}+{Mg3(CH2SiMe3)6(OCH2SiMe3)}-] (7) is also described, by the controlled exposure to oxygen of the monomeric compd. [(PMDETA)LiMg(CH2SiMe3)3] (6).
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  39. 39
    Armstrong, D. R.; Emerson, H. S.; Hernán-Gómez, A.; Kennedy, A. R.; Hevia, E. New Supramolecular Assemblies in Heterobimetallic Chemistry: Synthesis of a Homologous Series of Unsolvated Alkali-Metal Zincates. Dalton Trans. 2014, 43 (38), 14229– 14238,  DOI: 10.1039/C4DT01131G
    Google Scholar
    There is no corresponding record for this reference.
  40. 40
    Uzelac, M.; Borilovic, I.; Amores, M.; Cadenbach, T.; Kennedy, A. R.; Aromí, G.; Hevia, E. Structural and Magnetic Diversity in Alkali-Metal Manganate Chemistry: Evaluating Donor and Alkali-Metal Effects in Co-Complexation Processes. Chem.─Eur. J. 2016, 22 (14), 4843– 4854,  DOI: 10.1002/chem.201504956
    Google Scholar
    There is no corresponding record for this reference.
  41. 41
    Hong, S.; Marks, T. J. Organolanthanide-Catalyzed Hydroamination. Acc. Chem. Res. 2004, 37 (9), 673– 686,  DOI: 10.1021/ar040051r
    Google Scholar
    41
    Organolanthanide-Catalyzed Hydroamination
    Hong, Sukwon; Marks, Tobin J.
    Accounts of Chemical Research (2004), 37 (9), 673-686CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
    A review; organolanthanides are highly efficient catalysts for inter- and intramol. hydroamination of various C-C unsaturations such as alkenes, alkynes, allenes, and dienes. Attractive features of organolanthanide catalysts include very high turnover frequencies and excellent stereoselectivities, rendering this methodol. applicable to concise synthesis of naturally occurring alkaloids and other polycyclic azacycles. The general hydroamination mechanism involves turnover-limiting C-C multiple bond insertion into the Ln-N bond, followed by rapid protonolysis by other amine substrates. Sterically less encumbered ligand designs have been developed to improve reaction rates, and metallocene and nonmetallocene chiral lanthanide complexes have been synthesized for enantioselective hydroamination.
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  42. 42
    Barrett, A. G. M.; Brinkmann, C.; Crimmin, M. R.; Hill, M. S.; Hunt, P.; Procopiou, P. A. Heavier Group 2 Metals and Intermolecular Hydroamination: A Computational and Synthetic Assessment. J. Am. Chem. Soc. 2009, 131 (36), 12906– 12907,  DOI: 10.1021/ja905615a
    Google Scholar
    42
    Heavier Group 2 Metals and Intermolecular Hydroamination: A Computational and Synthetic Assessment
    Barrett, Anthony G. M.; Brinkmann, Christine; Crimmin, Mark R.; Hill, Michael S.; Hunt, Patricia; Procopiou, Panayiotis A.
    Journal of the American Chemical Society (2009), 131 (36), 12906-12907CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    A d. functional theory assessment of the use of the group 2 elements Mg, Ca, Sr, and Ba for the intermol. hydroamination of ethene indicated that the efficiency of the catalysis is dependent upon both the polarity and the deformability of the electron d. within the metal-substituent bonds of key intermediates and transition states. The validity of this anal. was supplemented by a preliminary study of the use of group 2 amides for the intermol. hydroamination of vinyl arenes. Although strontium was found to provide the highest catalytic activity, in line with the expectation provided by the theor. study, a preliminary kinetic anal. demonstrated that this is possibly a consequence of the increased radius and accessibility of this cation rather than a reflection of a reduced barrier for rate-detg. alkene insertion.
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  43. 43
    Zhang, X.; Emge, T. J.; Hultzsch, K. C. A Chiral Phenoxyamine Magnesium Catalyst for the Enantioselective Hydroamination/Cyclization of Aminoalkenes and Intermolecular Hydroamination of Vinyl Arenes. Angew. Chem., Int. Ed. 2012, 51 (2), 394– 398,  DOI: 10.1002/anie.201105079
    Google Scholar
    There is no corresponding record for this reference.
  44. 44
    Liu, B.; Roisnel, T.; Carpentier, J.-F.; Sarazin, Y. When Bigger Is Better: Intermolecular Hydrofunctionalizations of Activated Alkenes Catalyzed by Heteroleptic Alkaline Earth Complexes. Angew. Chem., Int. Ed. 2012, 51 (20), 4943– 4946,  DOI: 10.1002/anie.201200364
    Google Scholar
    44
    When Bigger Is Better: Intermolecular Hydrofunctionalizations of Activated Alkenes Catalyzed by Heteroleptic Alkaline Earth Complexes
    Liu, Bo; Roisnel, Thierry; Carpentier, Jean-Francois; Sarazin, Yann
    Angewandte Chemie, International Edition (2012), 51 (20), 4943-4946, S4943/1-S4943/28CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    New alk.-earth amido complexes catalyze the regioselective intermol. hydroamination and hydrophosphination of styrene and isoprene with unprecedented activities. The catalytic performances increased linearly with the size of the metal.
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  45. 45
    Germain, S.; Lecoq, M.; Schulz, E.; Hannedouche, J. Lithium-Catalyzed Anti-Markovnikov Intermolecular Hydroamination Reactions of Vinylarenes and Simple Secondary Amines. ChemCatChem 2017, 9 (10), 1749– 1753,  DOI: 10.1002/cctc.201700043
    Google Scholar
    There is no corresponding record for this reference.
  46. 46
    Horrillo-Martínez, P.; Hultzsch, K. C.; Gil, A.; Branchadell, V. Base-Catalyzed Anti-Markovnikov Hydroamination of Vinylarenes – Scope, Limitations and Computational Studies. Eur. J. Org Chem. 2007, 2007, 3311– 3325,  DOI: 10.1002/ejoc.200700147
    Google Scholar
    There is no corresponding record for this reference.
  47. 47
    Kumar, K.; Michalik, D.; Garcia Castro, I.; Tillack, A.; Zapf, A.; Arlt, M.; Heinrich, T.; Boettcher, H.; Beller, M. Biologically Active Compounds through Catalysis: Efficient Synthesis of N-(Heteroarylcarbonyl)-N′-(Arylalkyl)Piperazines. Chem.─Eur. J. 2004, 35 (24), 746– 757,  DOI: 10.1002/chin.200424144
    Google Scholar
    There is no corresponding record for this reference.
  48. 48

    For an Example of Incomplete Transamidation with NaFe(HMDS)3; see Ref (33). For Stoichiometric Experiments of NaFe(HMDS)3 with Piperidine; see Supporting Information.

    There is no corresponding record for this reference.
  49. 49
    Mulks, F. F.; Bole, L. J.; Davin, L.; Hernán-Gómez, A.; Kennedy, A.; García-Álvarez, J.; Hevia, E. Ambient Moisture Accelerates Hydroamination Reactions of Vinylarenes with Alkali-Metal Amides under Air. Angew. Chem., Int. Ed. 2020, 59 (43), 19021– 19026,  DOI: 10.1002/anie.202008512
    Google Scholar
    There is no corresponding record for this reference.
  50. 50
    Hujon, F.; Lyngdoh, R. H. D.; King, R. B. Iron-Iron Bond Lengths and Bond Orders in Diiron Lantern-Type Complexes with High Spin Ground States. Eur. J. Inorg. Chem. 2021, 2021, 848– 860,  DOI: 10.1002/ejic.202000897
    Google Scholar
    50
    Iron-Iron Bond Lengths and Bond Orders in Diiron Lantern-Type Complexes with High Spin Ground States
    Hujon, Fitzerald; Lyngdoh, Richard H. Duncan; King, R. Bruce
    European Journal of Inorganic Chemistry (2021), 2021 (9), 848-860CODEN: EJICFO; ISSN:1434-1948. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Diiron paddlewheel- or lantern-type complexes comprise an interesting subclass of binuclear iron complexes, existing with digonal, trigonal, and tetragonal ligand arrays. Exptl. known members show Fe-Fe bonds of lengths ranging from 2.13 to 2.73 Å, with Fe-Fe bond orders ranging from 0.5 to 2. Truncated models for 30 exptl. characterized diiron paddlewheel-type complexes have been studied by DFT using the M06-L functional, reproducing the Fe-Fe bond lengths quite well. In addn., we use DFT to treat three series of model diiron complexes Fe2Lx (x = 2, 3, 4) in various low-lying spin states, L being the unsubstituted formamidinate, guanidinate, and formate ligands (along with a series of axially ligated formate complexes) in order to predict ground state spin multiplicities, Fe-Fe bond lengths, and features of the ligand arrays. The ground states all have high spin multiplicities (septets, octets, and nonets). Formal bond order (fBO) values are suggested for the Fe-Fe bonds in these 61 complexes using an electron bookkeeping procedure, in addn. to the Fe-Fe bond orders obtained by metal-metal MO anal. for ground state species. Fe-Fe bond orders up to 3 are noted in some excited states. Deviations from D3h and D4h symmetry are noted for many trigonal and tetragonal complexes, being attributed to inherent Jahn-Teller distortions. The formamidinate and guanidinate series show many similarities, while the formate series differs from these two in several aspects. From these results, ranges are derived for Fe-Fe bond lengths of orders 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0. The Fe-Fe bond length ranges for these non-carbonyl lantern complexes are found to be appreciably lower than the corresponding ranges for diiron complexes with carbonyl ligands as compiled earlier from computational and exptl. results.
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  51. 51
    Kuppuswamy, S.; Bezpalko, M. W.; Powers, T. M.; Turnbull, M. M.; Foxman, B. M.; Thomas, C. M. Utilization of Phosphinoamide Ligands in Homobimetallic Fe and Mn Complexes: The Effect of Disparate Coordination Environments on Metal–Metal Interactions and Magnetic and Redox Properties. Inorg. Chem. 2012, 51 (15), 8225– 8240,  DOI: 10.1021/ic300776y
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    51
    Utilization of Phosphinoamide Ligands in Homobimetallic Fe and Mn Complexes: The Effect of Disparate Coordination Environments on Metal-Metal Interactions and Magnetic and Redox Properties
    Kuppuswamy, Subramaniam; Bezpalko, Mark W.; Powers, Tamara M.; Turnbull, Mark M.; Foxman, Bruce M.; Thomas, Christine M.
    Inorganic Chemistry (2012), 51 (15), 8225-8240CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    Homobimetallic phosphinoamide-bridged diiron and dimanganese complexes in which the two metals maintain different coordination environments were synthesized. Systematic variation of the steric and electronic properties of the phosphinoamide P and N substituents leads to structurally different complexes. Reaction of [iPrNKPPh2] (1) with MCl2 (M = Mn, Fe) affords the phosphinoamide-bridged bimetallic complexes [Mn(iPrNPPh2)3Mn(iPrNPPh2)] (3) and [Fe(iPrNPPh2)3Fe(iPrNPPh2)] (4). Complexes 3 and 4 are isostructural, with one metal center preferentially binding to the three amide ligands in a trigonal planar arrangement while the second metal center is ligated by three phosphine donors. A fourth phosphinoamide ligand caps the tetrahedral coordination sphere of the phosphine-ligated metal center. Mossbauer spectroscopy of complex 4 suggests that the metals in these complexes are best described as FeII centers. In contrast, treatment of MnCl2 or FeI2 with [MesNKPiPr2] (2) gives the halide-bridged species [(THF)Mn(μ-Cl)(MesNPiPr2)2Mn(MesNPiPr2)] (5) and [(THF)Fe(μ-I)(MesNPiPr2)2FeI] (7), resp. Use of FeCl2 in place of FeI2, however, leads exclusively to the C3-sym. complex [Fe(MesNPiPr2)3FeCl] (6), structurally similar to 4 but with a halide bound to the phosphine-ligated Fe center. The Mossbauer spectrum of 6 is also consistent with high spin FeII centers. Thus, in the case of the [iPrNPPh2]- and [MesNPiPr2]- ligands, zwitterionic complexes with the two metals in disparate coordination environments are preferentially formed. In the case of the more electron-rich ligand [iPrNPiPr2]-, complexes with a 2:1 mixed donor ligand arrangement, in which one of the ligand arms has reversed orientation relative to the previous examples, are formed exclusively when [iPrNLiPiPr2] (generated in situ) is treated with MCl2 (M = Mn, Fe): (THF)3LiCl[Mn(NiPrPiPr2)2(PiPr2NiPr)MnCl] (8) and [Fe(NiPrPiPr2)2(PiPr2NiPr)FeCl] (9). Bimetallic complexes 3-9 were structurally characterized using x-ray crystallog., revealing Fe-Fe interat. distances indicative of metal-metal bonding in complexes 6 and 9 (and perhaps 4, to a lesser extent). All of the complexes appear to adopt high spin electron configurations, and magnetic measurements indicate significant antiferromagnetic interactions in Mn2 complexes 5 and 8 and no discernible magnetic superexchange in Fe2 complex 4. The redox behavior of complexes 3-9 also was studied using cyclic voltammetry, and theor. studies (DFT) were performed to gain insight into the metal-metal interactions in these unique asym. complexes.
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Published November 11, 2024

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  • Abstract

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    Figure 1

    Figure 1. Hydroamination of unsaturated systems, (a) general hydroamination of alkenes, (b) intermolecular hydroamination with Lewis acid catalysis, (c) intramolecular hydroamination, and (d) intermolecular hydroamination with ferrates (this work).

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    Figure 2

    Figure 2. Bimetallic iron complexes in alkene hydroamination. (a) Synthesis of alkali metal trialkyl ferrates, ellipsoids are displayed at 50% probability, and all H atoms have been omitted for clarity. (b) Styrene hydroamination catalyzed by iron organometallic complexes. Conditions: styrene (0.2 mmol), piperidine (0.25 mmol), catalyst (0.02 mmol), and toluene (0.5 mL). Yields were measured by 1H NMR spectroscopy using hexamethylbenzene as the internal standard.

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    Figure 3

    Figure 3. Synthesis and crystal structure of [(TMEDA)NaFe(C5H10N)3]2 (I) and the proposed catalytic cycle. In the molecular structure, ellipsoids are displayed at 50% probability, and all H atoms have been omitted for clarity.

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    Figure 4

    Figure 4. Hydroamination of styrene derivatives with secondary amines. Conditions: vinylarene (0.2 mmol), amine (0.25 mmol), FeNa (0.02 mmol), toluene (0.5 mL), rt, 16 h. (a) Reaction performed at 50 °C, (b) reaction performed in THF, and (c) NMR yield using C6Me6 as the internal standard.

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  • References

    This article references 51 other publications.

    1. 1
      (a) Methodologies in Amine Synthesis: Challenges and Applications; Ricci, A., Ed.; Wiley: Hoboken, NJ, 2021.
      There is no corresponding record for this reference.
    2. 2
      Lawrence, S. A. Amines: Synthesis, Properties, and Applications; Cambridge University Press: Cambridge, 2004.
      There is no corresponding record for this reference.
    3. 3
      Johns, A. M.; Sakai, N.; Ridder, A.; Hartwig, J. F. Direct Measurement of the Thermodynamics of Vinylarene Hydroamination. J. Am. Chem. Soc. 2006, 128 (29), 9306– 9307,  DOI: 10.1021/ja062773e
      3
      Direct Measurement of the Thermodynamics of Vinylarene Hydroamination
      Johns, Adam M.; Sakai, Norio; Ridder, Andre; Hartwig, John F.
      Journal of the American Chemical Society (2006), 128 (29), 9306-9307CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The thermodn. for intermol. hydroamination of vinylarenes with arylamines were measured directly by conducting the addn. processes, as well as cleavage of the addn. products, under conditions in which amine, vinylarene, and phenethylamine are all present. The reaction of N-methylaniline with styrene is exothermic by ∼10 kcal/mol but nearly thermoneutral in free energy. The free energies for addns. of various primary arylamines to styrene and for addns. of primary arylamines to indene, dihydronaphthalene, and two vinylarenes range from 1.3 to -3.5 kcal/mol (K = 0.16-155 M-1). The steric properties of the nucleophile significantly influenced the equil. const. for addn., but the electronic properties of the nucleophile had a minor effect on this equil. const. These measurements led to the first successful intermol. addn. of aniline to indene and 1,2-dihydronaphthalene and shed light on factors requiring consideration when choosing substrates and reaction conditions for this transformation.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XmtVShs74%253D&md5=c9b6a68e28b5969f271590564b6b7db2
    4. 4
      Müller, T. E.; Hultzsch, K. C.; Yus, M.; Foubelo, F.; Tada, M. Hydroamination: Direct Addition of Amines to Alkenes and Alkynes. Chem. Rev. 2008, 108 (9), 3795– 3892,  DOI: 10.1021/cr0306788
      4
      Hydroamination: Direct Addition of Amines to Alkenes and Alkynes
      Mueller, Thomas E.; Hultzsch, Kai C.; Yus, Miguel; Foubelo, Francisco; Tada, Mizuki
      Chemical Reviews (Washington, DC, United States) (2008), 108 (9), 3795-3892CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. Hydroamination via direct addn. of amines to alkenes and alkynes was reviewed.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtVCnu7nI&md5=b80417785b6db24cb52835016ef4163d
    5. 5
      Huang, L.; Arndt, M.; Gooßen, K.; Heydt, H.; Gooßen, L. J. Late Transition Metal-Catalyzed Hydroamination and Hydroamidation. Chem. Rev. 2015, 115 (7), 2596– 2697,  DOI: 10.1021/cr300389u
      5
      Late Transition Metal-Catalyzed Hydroamination and Hydroamidation
      Huang, Liangbin; Arndt, Matthias; Goossen, Kaethe; Heydt, Heinrich; Goossen, Lukas J.
      Chemical Reviews (Washington, DC, United States) (2015), 115 (7), 2596-2697CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. This review examines recent developments in late transition metal-catalyzed hydroamination and -amidation reactions. In this review, usage of the term hydroamidation is not limited to the substrate classes of amides, sulfonamides, and phosphonamides, but extended to structurally related compds. with a similar pKa range and reactivity, such as carbamates, lactams, ureas, amidines, guanidines, etc.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXjsFChurY%253D&md5=52c63d6ba025e1973c8fec49a9868e31
    6. 6
      Trowbridge, A.; Walton, S. M.; Gaunt, M. J. New Strategies for the Transition-Metal Catalyzed Synthesis of Aliphatic Amines. Chem. Rev. 2020, 120 (5), 2613– 2692,  DOI: 10.1021/acs.chemrev.9b00462
      6
      New Strategies for the Transition-Metal Catalyzed Synthesis of Aliphatic Amines
      Trowbridge, Aaron; Walton, Scarlett M.; Gaunt, Matthew J.
      Chemical Reviews (Washington, DC, United States) (2020), 120 (5), 2613-2692CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. In light of the ever-increasing importance of aliph. amines across the range of chem. sciences, this review aims to provide a concise overview of modern transition-metal catalyzed approaches to alkylamine synthesis and their functionalization. Selected examples of amine bond forming reactions include, hydroamination and hydroaminoalkylation, transition-metal catalyzed C(sp3)-H functionalization and transition-metal catalyzed visible-light-mediated light photoredox catalysis.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXivFyku7c%253D&md5=a01eb2f330f81c459fb35e26a306f007
    7. 7
      Escorihuela, J.; Lledós, A.; Ujaque, G. Anti-Markovnikov Intermolecular Hydroamination of Alkenes and Alkynes: A Mechanistic View. Chem. Rev. 2023, 123 (15), 9139– 9203,  DOI: 10.1021/acs.chemrev.2c00482
      There is no corresponding record for this reference.
    8. 8
      Gui, J.; Pan, C.-M.; Jin, Y.; Qin, T.; Lo, J. C.; Lee, B. J.; Spergel, S. H.; Mertzman, M. E.; Pitts, W. J.; La Cruz, T. E.; Schmidt, M. A.; Darvatkar, N.; Natarajan, S. R.; Baran, P. S. Practical Olefin Hydroamination with Nitroarenes. Science 2015, 348 (6237), 886– 891,  DOI: 10.1126/science.aab0245
      8
      Practical olefin hydroamination with nitroarenes
      Gui, Jinghan; Pan, Chung-Mao; Jin, Ying; Qin, Tian; Lo, Julian C.; Lee, Bryan J.; Spergel, Steven H.; Mertzman, Michael E.; Pitts, William J.; La Cruz, Thomas E.; Schmidt, Michael A.; Darvatkar, Nitin; Natarajan, Swaminathan R.; Baran, Phil S.
      Science (Washington, DC, United States) (2015), 348 (6237), 886-891CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      The synthesis and functionalization of amines are fundamentally important in a vast range of chem. contexts. We present an amine synthesis that repurposes two simple feedstock building blocks: olefins and nitro(hetero)arenes. Using readily available reactants in an operationally simple procedure, the protocol smoothly yields secondary amines in a formal olefin hydroamination. Because of the presumed radical nature of the process, hindered amines can easily be accessed in a highly chemoselective transformation. A screen of more than 100 substrate combinations showcases tolerance of numerous unprotected functional groups such as alcs., amines, and even boronic acids. This process is orthogonal to other aryl amine syntheses, such as the Buchwald-Hartwig, Ullmann, and classical amine-carbonyl reductive aminations, as it tolerates aryl halides and carbonyl compds.
      >> More from SciFinder ®
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    9. 9
      Zhu, K.; Shaver, M. P.; Thomas, S. P. Chemoselective Nitro Reduction and Hydroamination Using a Single Iron Catalyst. Chem. Sci. 2016, 7 (5), 3031– 3035,  DOI: 10.1039/C5SC04471E
      9
      Chemoselective nitro reduction and hydroamination using a single iron catalyst
      Zhu, Kailong; Shaver, Michael P.; Thomas, Stephen P.
      Chemical Science (2016), 7 (5), 3031-3035CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
      The redn. and reductive addn. (formal hydroamination) of functionalized nitroarenes was reported using a simple and bench-stable iron(III) catalyst and silane. The redn. was chemoselective for nitro groups over an array of reactive functionalities (ketone, ester, amide, nitrile, sulfonyl and aryl halide). The high activity of this earth-abundant metal catalyst also facilitated a follow-on reaction in the reductive addn. of nitroarenes to alkenes, giving efficient formal hydroamination of olefins under mild conditions. Both reactions offered significant improvements in catalytic activity and chemoselectivity and the utility of these catalysts in facilitating two challenging reactions supported an important mechanistic overlap.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xhtl2qtLk%253D&md5=690f4839a14ec594ef43ec1dee48f3f9
    10. 10
      Zhu, K.; Shaver, M. P.; Thomas, S. P. Amine-Bis(Phenolate) Iron(III)-Catalyzed Formal Hydroamination of Olefins. Chem.─Asian J. 2016, 11 (7), 977– 980,  DOI: 10.1002/asia.201501098
      There is no corresponding record for this reference.
    11. 11
      Obradors, C.; Martinez, R. M.; Shenvi, R. A. Ph(i-PrO)SiH2: An Exceptional Reductant for Metal-Catalyzed Hydrogen Atom Transfers. J. Am. Chem. Soc. 2016, 138 (14), 4962– 4971,  DOI: 10.1021/jacs.6b02032
      11
      Ph(i-PrO)SiH2: An Exceptional Reductant for Metal-Catalyzed Hydrogen Atom Transfers
      Obradors, Carla; Martinez, Ruben M.; Shenvi, Ryan A.
      Journal of the American Chemical Society (2016), 138 (14), 4962-4971CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      We report the discovery of an outstanding reductant for metal-catalyzed radical hydrofunctionalization reactions. Observations of unexpected silane solvolysis distributions in the HAT-initiated hydrogenation of alkenes reveal that phenylsilane is not the kinetically preferred reductant in many of these transformations. Instead, isopropoxy(phenyl)silane forms under the reaction conditions, suggesting that alcs. function as important silane ligands to promote the formation of metal hydrides. Study of its reactivity showed that isopropoxy(phenyl)silane is an exceptionally efficient stoichiometric reductant, and it is now possible to significantly decrease catalyst loadings, lower reaction temps., broaden functional group tolerance, and use diverse, aprotic solvents in iron- and manganese-catalyzed hydrofunctionalizations. As representative examples, we have improved the yields and rates of alkene redn., hydration, hydroamination, and conjugate addn. Discovery of this broadly applicable, chemoselective, and solvent-versatile reagent should allow an easier interface with existing radical reactions. Finally, isotope-labeling expts. rule out the alternative hypothesis of hydrogen atom transfer from a redox-active β-diketonate ligand in the HAT step. Instead, initial HAT from a metal hydride to directly generate a carbon-centered radical appears to be the most reasonable hypothesis.
      >> More from SciFinder ®
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    12. 12
      Huehls, C. B.; Lin, A.; Yang, J. Iron-Catalyzed Intermolecular Hydroamination of Styrenes. Org. Lett. 2014, 16 (14), 3620– 3623,  DOI: 10.1021/ol5013907
      There is no corresponding record for this reference.
    13. 13
      Luescher, M. U.; Gallou, F.; Lipshutz, B. H. The Impact of Earth-Abundant Metals as a Replacement for Pd in Cross Coupling Reactions. Chem. Sci. 2024, 15 (24), 9016– 9025,  DOI: 10.1039/D4SC00482E
      There is no corresponding record for this reference.
    14. 14
      Bullock, R. M.; Chen, J. G.; Gagliardi, L.; Chirik, P. J.; Farha, O. K.; Hendon, C. H.; Jones, C. W.; Keith, J. A.; Klosin, J.; Minteer, S. D.; Morris, R. H.; Radosevich, A. T.; Rauchfuss, T. B.; Strotman, N. A.; Vojvodic, A.; Ward, T. R.; Yang, J. Y.; Surendranath, Y. Using Nature’s Blueprint to Expand Catalysis with Earth-Abundant Metals. Science 2020, 369 (6505), eabc3183  DOI: 10.1126/science.abc3183
      There is no corresponding record for this reference.
    15. 15
      Zotto, C. D.; Michaux, J.; Zarate-Ruiz, A.; Gayon, E.; Virieux, D.; Campagne, J.-M.; Terrasson, V.; Pieters, G.; Gaucher, A.; Prim, D. FeCl3-Catalyzed Addition of Nitrogen and 1,3-Dicarbonyl Nucleophiles to Olefins. J. Organomet. Chem. 2011, 696 (1), 296– 304,  DOI: 10.1016/j.jorganchem.2010.09.031
      There is no corresponding record for this reference.
    16. 16
      Michaux, J.; Terrasson, V.; Marque, S.; Wehbe, J.; Prim, D.; Campagne, J.-M. Intermolecular FeCl3-Catalyzed Hydroamination of Styrenes. Eur. J. Org Chem. 2007, 2007, 2601– 2603,  DOI: 10.1002/ejoc.200700023
      There is no corresponding record for this reference.
    17. 17
      Komeyama, K.; Morimoto, T.; Takaki, K. A. A Simple and Efficient Iron-Catalyzed Intramolecular Hydroamination of Unactivated Olefins. Angew. Chem., Int. Ed. 2006, 45 (18), 2938– 2941,  DOI: 10.1002/anie.200503789
      There is no corresponding record for this reference.
    18. 18
      Lepori, C.; Guillot, R.; Hannedouche, J. 1-symmetric β-Diketiminatoiron(II) Complexes for Hydroamination of Primary Alkenylamines. Adv. Synth. Catal. 2019, 361 (4), 714– 719,  DOI: 10.1002/adsc.201801464
      There is no corresponding record for this reference.
    19. 19
      Lepori, C.; Bernoud, E.; Guillot, R.; Tobisch, S.; Hannedouche, J. Experimental and Computational Mechanistic Studies of the β-Diketiminatoiron(II)-Catalysed Hydroamination of Primary Aminoalkenes. Chem.─Eur. J. 2019, 25 (3), 835– 844,  DOI: 10.1002/chem.201804681
      There is no corresponding record for this reference.
    20. 20
      Bernoud, E.; Oulié, P.; Guillot, R.; Mellah, M.; Hannedouche, J. Well-Defined Four-Coordinate Iron(II) Complexes For Intramolecular Hydroamination of Primary Aliphatic Alkenylamines. Angew. Chem., Int. Ed. 2014, 53 (19), 4930– 4934,  DOI: 10.1002/anie.201402089
      20
      Well-defined four-coordinate iron(II) complexes for intramolecular hydroamination of primary aliphatic alkenylamines
      Bernoud, Elise; Oulie, Pascal; Guillot, Regis; Mellah, Mohamed; Hannedouche, Jerome
      Angewandte Chemie, International Edition (2014), 53 (19), 4930-4934CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A novel well-defined four-coordinate β-diketiminato iron(II) alkyl complex was shown to be an excellent precatalyst for the highly selective cyclohydroamination of primary aliph. alkenylamines at mild temps. (70-90°). Both empirical kinetic analyses and the reactivity of an isolated iron(II) amido-alkene dimer, [LFe(NHCH2CPh2CH2CH:CH2)]2 [HL = 2,4-bis(2,4,6-trimethylphenylimino)pentane], favor a stepwise σ-insertive mechanism that entails migratory insertion of the pendant alkene into an iron-amido bond assocd. with a rate-detg. aminolysis step.
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    21. 21
      Davin, L.; Hernán-Gómez, A.; McLaughlin, C.; Kennedy, A. R.; McLellan, R.; Hevia, E. Alkali Metal and Stoichiometric Effects in Intermolecular Hydroamination Catalysed by Lithium, Sodium and Potassium Magnesiates. Dalton Trans. 2019, 48 (23), 8122– 8130,  DOI: 10.1039/C9DT00923J
      21
      Alkali metal and stoichiometric effects in intermolecular hydroamination catalysed by lithium, sodium and potassium magnesiates
      Davin, Laia; Hernan-Gomez, Alberto; McLaughlin, Calum; Kennedy, Alan R.; McLellan, Ross; Hevia, Eva
      Dalton Transactions (2019), 48 (23), 8122-8130CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
      In the presence of lithium, sodium, and potassium alkylmagnesium compds. such as [(PMDETA)2K2Mg(CH2SiMe3)4] (I), diphenylacetylene and styrene underwent regioselective and stereoselective hydroamination reactions with cyclic amines such as piperidine at ambient temp. to yield enamines and amines; the effect of counterion and the order of the magnesium reagent on the hydroamination reactions was studied. The high reactivity of bimetallic alkylmagnesium compds. as hydroamination catalysts contrasts with the complete lack of catalytic ability of neutral Mg(CH2SiMe3)2. The alkali metal (Li, Na, or K) of the bimetallic alkylmagnesium compd. strongly affects its ability to act as a catalyst, indicating that the alkali metal counterion is not a spectator. Potential intermediates were identified, and their crystal structures detd. in some cases. The enhanced catalytic activity of I is rationalized by the higher nucleophilicity of the dianion magnesiates formed in situ during hydroamination and by the ability of potassium ion to engage in π-interactions with the alkyne or alkene and thus to enhance its susceptibility towards nucleophilic attack by amide anions.
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    22. 22
      Sears, J. D.; Muñoz, S. B., III; Daifuku, S. L.; Shaps, A. A.; Carpenter, S. H.; Brennessel, W. W.; Neidig, M. L. The Effect of β-Hydrogen Atoms on Iron Speciation in Cross-Couplings with Simple Iron Salts and Alkyl Grignard Reagents. Angew. Chem., Int. Ed. 2019, 58 (9), 2769– 2773,  DOI: 10.1002/anie.201813578
      22
      The Effect of β-Hydrogen Atoms on Iron Speciation in Cross-Couplings with Simple Iron Salts and Alkyl Grignard Reagents
      Sears, Jeffrey D.; Munoz, Salvador B., III; Daifuku, Stephanie L.; Shaps, Ari A.; Carpenter, Stephanie H.; Brennessel, William W.; Neidig, Michael L.
      Angewandte Chemie, International Edition (2019), 58 (9), 2769-2773CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The effects of β-H-contg. alkyl Grignard reagents in simple ferric salt cross-couplings were elucidated. The reaction of FeCl3 with EtMgBr in THF gives the cluster species [Fe8Et12]2-, a rare example of a structurally characterized metal complex with bridging Et ligands. Analogous reactions in the presence of NMP, a key additive for effective cross-coupling with simple ferric salts and β-H-contg. alkyl nucleophiles, gave [FeEt3]-. Reactivity studies demonstrate the effectiveness of [FeEt3]- in rapidly and selectively forming the cross-coupled product upon reaction with electrophiles. The identification of Fe-ate species with EtMgBr analogous to those previously obsd. with MeMgBr is a crit. insight, indicating that analogous Fe species can be operative in catalysis for these two classes of alkyl nucleophiles.
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    23. 23
      Bedford, R. B.; Brenner, P. B.; Carter, E.; Cogswell, P. M.; Haddow, M. F.; Harvey, J. N.; Murphy, D. M.; Nunn, J.; Woodall, C. H. TMEDA in Iron-Catalyzed Kumada Coupling: Amine Adduct versus Homoleptic “Ate” Complex Formation. Angew. Chem., Int. Ed. 2014, 53 (7), 1804– 1808,  DOI: 10.1002/anie.201308395
      23
      TMEDA in Iron-Catalyzed Kumada Coupling: Amine Adduct versus Homoleptic "ate" Complex Formation
      Bedford, Robin B.; Brenner, Peter B.; Carter, Emma; Cogswell, Paul M.; Haddow, Mairi F.; Harvey, Jeremy N.; Murphy, Damien M.; Nunn, Joshua; Woodall, Christopher H.
      Angewandte Chemie, International Edition (2014), 53 (7), 1804-1808CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The reactions of Fe chlorides with mesityl Grignard reagents and tetramethylethylenediamine (TMEDA) under catalytically relevant conditions tend to yield the homoleptic ate complex [Fe(mes)3]- (mes = mesityl) rather than adducts of the diamine, and it is this ate complex that accounts for the catalytic activity. Both [Fe(mes)3]- and the related complex [Fe(Bn)3]- (Bn = benzyl) react faster with representative electrophiles than the equiv. neutral [FeR2(TMEDA)] complexes. Fe(I) species are obsd. under catalytically relevant conditions with both benzyl and smaller aryl Grignard reagents. The x-ray structures of [Fe(Bn)3]- and [Fe(Bn)4]- were detd.; [Fe(Bn)4]- is the 1st homoleptic σ-hydrocarbyl Fe(III) complex that was structurally characterized.
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    24. 24
      Sears, J. D.; Muñoz, S. B., III; Cuenca, M. C. A.; Brennessel, W. W.; Neidig, M. L. Synthesis and Characterization of a Sterically Encumbered Homoleptic Tetraalkyliron(III) Ferrate Complex. Polyhedron 2019, 158, 91– 96,  DOI: 10.1016/j.poly.2018.10.041
      24
      Synthesis and characterization of a sterically encumbered homoleptic tetraalkyliron(III) ferrate complex
      Sears, Jeffrey D.; Munoz, Salvador B. III; Cuenca, Maria Camila Aguilera; Brennessel, William W.; Neidig, Michael L.
      Polyhedron (2019), 158 (), 91-96CODEN: PLYHDE; ISSN:0277-5387. (Elsevier Ltd.)
      Homoleptic iron-alkyl complexes have been implicated as key intermediates in iron-catalyzed cross-coupling with simple iron salts. Tetraalkyliron(III) ferrate species have been accessible with either Me or benzyl ligands, where the former complex is S = 3/2 and distorted square planar while the latter is a S = 5/2 distorted tetrahedral species. In the current study, a new tetraalkyliron(III) complex is synthesized contg. modified methylene substituents that incorporate large trimethylsilyl (TMS) groups to further probe steric and electronic ligand effects in tetraalkyliron(III) complexes by increasing the electron-donating ability of the ligand while retaining steric bulk. Detailed structural and DFT studies provide insight into electronic structure and bonding of the four-coordinate trimethylsilylmethyl iron(III) complex compared to the previously reported analogs contg. Me and benzyl ligands.
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    25. 25
      Fürstner, A.; Martin, R.; Krause, H.; Seidel, G.; Goddard, R.; Lehmann, C. W. Preparation, Structure, and Reactivity of Nonstabilized Organoiron Compounds. Implications for Iron-Catalyzed Cross Coupling Reactions. J. Am. Chem. Soc. 2008, 130 (27), 8773– 8787,  DOI: 10.1021/ja801466t
      25
      Preparation, Structure, and Reactivity of Nonstabilized Organoiron Compounds. Implications for Iron-Catalyzed Cross Coupling Reactions
      Fuerstner, Alois; Martin, Ruben; Krause, Helga; Seidel, Gunter; Goddard, Richard; Lehmann, Christian W.
      Journal of the American Chemical Society (2008), 130 (27), 8773-8787CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      A series of unprecedented organoiron complexes of the formal oxidn. states -2, 0, +1, +2, and +3 is presented, which are largely devoid of stabilizing ligands and, in part, also electronically unsatd. (14-, 16-, 17- and 18-electron counts). Specifically, it is shown that nucleophiles unable to undergo β-hydride elimination, such as MeLi, PhLi, or PhMgBr, rapidly reduce Fe(3+) to Fe(2+) and then exhaustively alkylate the metal center. The resulting homoleptic organoferrate complexes [(Me4Fe)(MeLi)][Li(OEt2)]2 (3) and [Ph4Fe][Li(Et2O)2][Li(1,4-dioxane)] (5) could be characterized by x-ray crystal structure anal. However, these exceptionally sensitive compds. turned out to be only moderately nucleophilic, transferring their org. ligands to activated electrophiles only, while being unable to alkylate (hetero)aryl halides unless they are very electron deficient. In striking contrast, Grignard reagents bearing alkyl residues amenable to β-hydride elimination reduce FeXn (n = 2, 3) to clusters of the formal compn. [Fe(MgX)2]n. The behavior of these intermetallic species can be emulated by structurally well-defined lithium ferrate complexes of the type [Fe(C2H4)4][Li(tmeda)]2 (8), [Fe(cod)2][Li(dme)]2 (9), [CpFe(C2H4)2][Li(tmeda)] (7), [CpFe(cod)][Li(dme)] (11), or [Cp*Fe(C2H4)2][Li(tmeda)] (14). Such electron-rich complexes, which are distinguished by short intermetallic Fe-Li bonds, were shown to react with aryl chlorides and allyl halides; the structures and reactivity patterns of the resulting organoiron compds. provide first insights into the elementary steps of low valent iron-catalyzed cross coupling reactions of aryl, alkyl, allyl, benzyl, and propargyl halides with organomagnesium reagents. However, the acquired data suggest that such C-C bond formations can occur, a priori, along different catalytic cycles shuttling between metal centers of the formal oxidn. states Fe(+1)/Fe(+3), Fe(0)/Fe(+2), and Fe(-2)/Fe(0). Since these different manifolds are likely interconnected, an unambiguous decision as to which redox cycle dominates in soln. remains difficult, even though iron complexes of the lowest accessible formal oxidn. states promote the reactions most effectively.
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    26. 26
      Muñoz, S. B., III; Daifuku, S. L.; Sears, J. D.; Baker, T. M.; Carpenter, S. H.; Brennessel, W. W.; Neidig, M. L. The N-Methylpyrrolidone (NMP) Effect in Iron-Catalyzed Cross-Coupling with Simple Ferric Salts and MeMgBr. Angew. Chem., Int. Ed. 2018, 57 (22), 6496– 6500,  DOI: 10.1002/anie.201802087
      26
      The N-Methylpyrrolidone (NMP) Effect in Iron-Catalyzed Cross-Coupling with Simple Ferric Salts and MeMgBr
      Munoz, Salvador B., III; Daifuku, Stephanie L.; Sears, Jeffrey D.; Baker, Tessa M.; Carpenter, Stephanie H.; Brennessel, William W.; Neidig, Michael L.
      Angewandte Chemie, International Edition (2018), 57 (22), 6496-6500CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The use of N-methylpyrrolidone (NMP) as a co-solvent in ferric salt catalyzed cross-coupling reactions is crucial for achieving the highly selective, preparative scale formation of cross-coupled product in reactions utilizing alkyl Grignard reagents. Despite the crit. importance of NMP, the mol. level effect of NMP on in situ formed and reactive iron species that enables effective catalysis remains undefined. Herein, we report the isolation and characterization of a novel trimethyliron(II) ferrate species, [Mg(NMP)6][FeMe3]2 (1), which forms as the major iron species in situ in reactions of Fe(acac)3 and MeMgBr under catalytically relevant conditions where NMP is employed as a co-solvent. Importantly, combined GC anal. and 57Fe Moessbauer spectroscopic studies identified 1 as a highly reactive iron species for the selective formation generating cross-coupled product. These studies demonstrate that NMP does not directly interact with iron as a ligand in catalysis but, alternatively, interacts with the magnesium cations to preferentially stabilize the formation of 1 over [Fe8Me12]- cluster generation, which occurs in the absence of NMP.
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    27. 27
      Al-Afyouni, M. H.; Fillman, K. L.; Brennessel, W. W.; Neidig, M. L. Isolation and Characterization of a Tetramethyliron(III) Ferrate: An Intermediate in the Reduction Pathway of Ferric Salts with MeMgBr. J. Am. Chem. Soc. 2014, 136 (44), 15457– 15460,  DOI: 10.1021/ja5080757
      27
      Isolation and Characterization of a Tetramethyliron(III) Ferrate: An Intermediate in the Reduction Pathway of Ferric Salts with MeMgBr
      Al-Afyouni, Malik H.; Fillman, Kathlyn L.; Brennessel, William W.; Neidig, Michael L.
      Journal of the American Chemical Society (2014), 136 (44), 15457-15460CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      While Fe-catalyzed Kumada cross-coupling reactions with simple Fe salts were known since the early 1970s, the nature of the in situ-formed Fe species remains elusive. Herein, the authors report the synthesis of the homoleptic tetralkyliron(III) ferrate complex [MgCl(THF)5][FeMe4] from the reaction of FeCl3 with MeMgBr in THF. Upon warming, this distorted square-planar S = 3/2 species converts to the S = 1/2 species originally obsd. by Kochi and coworkers with concomitant formation of ethane, consistent with its intermediacy in the redn. pathway of FeCl3 to generate the reduced Fe species involved in catalysis.
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    28. 28
      Rousseau, L.; Herrero, C.; Clémancey, M.; Imberdis, A.; Blondin, G.; Lefèvre, G. Evolution of Ate-Organoiron(II) Species towards Lower Oxidation States: Role of the Steric and Electronic Factors. Chem.─Eur. J. 2020, 26 (11), 2417– 2428
      There is no corresponding record for this reference.
    29. 29
      Maddock, L. C. H.; Borilovic, I.; McIntyre, J.; Kennedy, A. R.; Aromí, G.; Hevia, E. Synthetic, Structural and Magnetic Implications of Introducing 2,2′-Dipyridylamide to Sodium-Ferrate Complexes. Dalton Trans. 2017, 46 (20), 6683– 6691,  DOI: 10.1039/C7DT01319A
      29
      Synthetic, structural and magnetic implications of introducing 2,2'-dipyridylamide to sodium-ferrate complexes
      Maddock, Lewis C. H.; Borilovic, Ivana; McIntyre, Jamie; Kennedy, Alan R.; Aromi, Guillem; Hevia, Eva
      Dalton Transactions (2017), 46 (20), 6683-6691CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
      Using a transamination approach to access novel Fe(II) complexes, this study presents the synthesis, x-ray crystallog. and magnetic characterization of new Fe complexes contg. the multifunctional 2,2-dipyridylamide (DPA) ligand using Fe bis(amide) [{Fe(HMDS)2}2] and Na ferrate [{NaFe(HMDS)3}∞] (1) as precursors (HMDS = 1,1,1,3,3,3-hexamethyldisilazide). Reactions of DPA(H) with 1 show exceptionally good stoichiometric control, allowing access to heteroleptic [(THF)2·NaFe(DPA)(HMDS)2] (3) and homoleptic [{THF·NaFe(DPA)3}∞] (4) by using 1 and 3 equiv of DPA(H), resp. Linking this methodol. and co-complexation, which is a more widely used approach to prep. heterobimetallic complexes, 3 can also be prepd. by combining NaHMDS with heteroleptic [{Fe(DPA)(HMDS)}2] (2). In turn, 2 was also synthesized and structurally defined by reacting [{Fe(HMDS)2}2] with two equiv. of DPA(H). Structural studies demonstrate the coordination flexibility of the N-bridged bis(heterocycle) ligand DPA, with 2 and 3 exhibiting discrete monomeric motifs, whereas 4 displays a much more intricate supramol. structure, with one of its DPA ligands coordinating in an anti/anti fashion (as opposed to 2 and 3 where DPA shows a syn/syn conformation), which facilitates propagation of the structure via its central amido N. Magnetic studies confirmed the high-spin electron configuration of the Fe(II) centers in all three compds. and revealed the existence of weak ferromagnetic interactions in dinuclear compd. 2 (J = 1.01 cm-1).
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    30. 30
      Maddock, L. C. H.; Nixon, T.; Kennedy, A. R.; Probert, M. R.; Clegg, W.; Hevia, E. Utilising Sodium-Mediated Ferration for Regioselective Functionalisation of Fluoroarenes via C–H and C–F Bond Activations. Angew. Chem., Int. Ed. 2018, 57 (1), 187– 191,  DOI: 10.1002/anie.201709750
      30
      Utilising Sodium-Mediated Ferration for Regioselective Functionalisation of Fluoroarenes via C-H and C-F Bond Activations
      Maddock, Lewis C. H.; Nixon, Tracy; Kennedy, Alan R.; Probert, Michael R.; Clegg, William; Hevia, Eva
      Angewandte Chemie, International Edition (2018), 57 (1), 187-191CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Pairing iron bis(amide) Fe(HMDS)2 with Na(HMDS) to form new sodium ferrate base [(dioxane)0.5NaFe(HMDS)3] (1, I) enables regioselective mono and di-ferration (via direct Fe-H exchange) of a wide range of fluoroarom. substrates under mild reaction conditions. Trapping of several ferrated intermediates has provided key insight into how synchronized Na/Fe cooperation operates in these transformations. Furthermore, using excess 1 at 80 °C switches on a remarkable cascade process inducing the collective twofold C-H/threefold C-F bond activations, where each C-H bond is transformed to a C-Fe bond whereas each C-F bond is transformed into a C-N bond.
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    31. 31
      Maddock, L. C. H.; Kennedy, A.; Hevia, E. Lithium-Mediated Ferration of Fluoroarenes. Chimia 2020, 74 (11), 866,  DOI: 10.2533/chimia.2020.866
      31
      Lithium-mediated ferrationof fluoroarenes
      Maddock, Lewis C. H.; Kennedy, Alan; Hevia, Eva
      Chimia (2020), 74 (11), 866-870CODEN: CHIMAD ISSN:. (Swiss Chemical Society)
      While fluoroaryl fragments are ubiquitous in many pharmaceuticals, the deprotonation of fluoroarenes using organolithium bases constitutes an important challenge in polar organometallic chem. This has been widely attributed to the low stability of the in situ generated aryl lithium intermediates that even at -78 °C can undergo unwanted side reactions. Herein, pairing lithium amide LiHMDS (HMDS = N{SiMe3}2) with FeII(HMDS)2 enables the selective deprotonation at room temp. of pentafluorobenzene and 1,3,5-trifluorobenzene via the mixed-metal base [(dioxane)LiFe(HMDS)3] (1) (dioxane = 1,4-dioxane). Structural elucidation of the organo-metallic intermediates [(dioxane)Li(HMDS)2Fe(ArF)] (ArF = C6F5, 2; 1,3,5-F3-C6H2, 3) prior electrophilic interception demonstrates that these deprotonations are actually ferrations, with Fe occupying the position previously filled by a hydrogen atom. Notwithstanding, the presence of lithium is essential for the reactions to take place as FeII(HMDS)2 on its own is completely inert towards the metalation of these substrates. Interestingly 2 and 3 are thermally stable and they do not undergo benzyne formation via LiF elimination.
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    32. 32
      Maddock, L. C. H.; Mu, M.; Kennedy, A. R.; García-Melchor, M.; Hevia, E. Facilitating the Ferration of Aromatic Substrates through Intramolecular Sodium Mediation. Angew. Chem., Int. Ed. 2021, 60 (28), 15296– 15301,  DOI: 10.1002/anie.202104275
      There is no corresponding record for this reference.
    33. 33
      Maddock, L. C. H.; Morton, R.; Kennedy, A. R.; Hevia, E. Lateral Metallation and Redistribution Reactions of Sodium Ferrates Containing Bulky 2,6-Diisopropyl-N-(Trimethylsilyl)Anilide Ligands. Chem.─Eur. J. 2021, 27 (61), 15181– 15187,  DOI: 10.1002/chem.202102328
      There is no corresponding record for this reference.
    34. 34
      Borys, A. M.; Hevia, E. Exploiting Chemical Cooperativity in Main-Group Bimetallic Catalysis. Trends Chem. 2021, 3 (10), 803– 806,  DOI: 10.1016/j.trechm.2021.07.006
      There is no corresponding record for this reference.
    35. 35
      Gil-Negrete, J. M.; Hevia, E. Main Group Bimetallic Partnerships for Cooperative Catalysis. Chem. Sci. 2021, 12 (6), 1982– 1992,  DOI: 10.1039/D0SC05116K
      35
      Main group bimetallic partnerships for cooperative catalysis
      Gil-Negrete, Jose M.; Hevia, Eva
      Chemical Science (2021), 12 (6), 1982-1992CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
      A review. Over the past decade s-block metal catalysis has undergone a transformation from being an esoteric curiosity to a well-established and consolidated field towards sustainable synthesis. Earth-abundant metals such as Ca, Mg, and Al have shown eye-opening catalytic performances in key catalytic processes such as hydrosilylation, hydroamination or alkene polymn. In parallel to these studies, s-block mixed-metal reagents have also been attracting widespread interest from scientists. These bimetallic reagents effect many cornerstone org. transformations, often providing enhanced reactivities and better chemo- and regioselectivities than conventional monometallic reagents. Despite a significant no. of synthetic advances to date, most efforts have focused primarily on stoichiometric transformations. Merging these two exciting areas of research, this Perspective Article provides an overview on the emerging concept of s/p-block cooperative catalysis. Showcasing recent contributions from several research groups across the world, the untapped potential that these systems can offer in catalytic transformations is discussed with special emphasis placed on how synergistic effects can operate and the special roles played by each metal in these transformations.
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    36. 36
      Bart, S. C.; Hawrelak, E. J.; Schmisseur, A. K.; Lobkovsky, E.; Chirik, P. J. Synthesis, Reactivity, and Solid State Structures of Four-Coordinate Iron(II) and Manganese(II) Alkyl Complexes. Organometallics 2004, 23 (2), 237– 246,  DOI: 10.1021/om034188h
      36
      Synthesis, Reactivity, and Solid State Structures of Four-Coordinate Iron(II) and Manganese(II) Alkyl Complexes
      Bart, Suzanne C.; Hawrelak, Eric J.; Schmisseur, Amanda K.; Lobkovsky, Emil; Chirik, Paul J.
      Organometallics (2004), 23 (2), 237-246CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
      Synthesis and characterization of new, four-coordinate, high-spin iron(II) and manganese(II) complexes of the general form L2MR2 (L2 = neutral chelating ligand, R = alkyl) are described. Alkylation of the α-diimine complex, [ArN:C(Me)-C(Me):NAr]FeCl2 (Ar = 2,6-diisopropylphenyl), as well as the enantiopure iron dichloride compds., (-)-(sparteine)FeCl2 and (S)-(tBuBox)FeCl2 ((S)-(tBuBox) = 2,2-bis[2-[4(S)-(R')-1,3-oxazolinyl]propane]), with LiCH2SiMe3 afforded the corresponding dialkyl derivs. Soln. magnetic susceptibility measurements and x-ray diffraction studies reveal each of the new iron(II) bis(trimethylsilylmethyl) complexes to be high-spin, S = 2, tetrahedral mols. In addn. (-)-(sparteine)Fe(CH2CMe3)2, (-)-(sparteine)Fe(CH2C6H5)2, and (S)-(tBuBox)Fe(CH2C6H5)2 were also prepd. and characterized by NMR spectroscopy and elemental anal. An enantiopure, high-spin, tetrahedral manganese(II) dialkyl complex, (-)-(sparteine)Mn(CH2SiMe3)2, has also been synthesized. The catalytic activity of the new iron complexes in carbon-carbon bond forming processes has been evaluated, and stoichiometric reactions of the dialkyls with olefins, carbon monoxide, and the Lewis acid B(C6F5)3 have been examd.
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    37. 37
      Alborés, P.; Carrella, L. M.; Clegg, W.; García-Álvarez, P.; Kennedy, A. R.; Klett, J.; Mulvey, R. E.; Rentschler, E.; Russo, L. Direct C–H Metalation with Chromium(II) and Iron(II): Transition-Metal Host/Benzenediide Guest Magnetic Inverse-Crown Complexes. Angew. Chem., Int. Ed. 2009, 48 (18), 3317– 3321,  DOI: 10.1002/anie.200805566
      There is no corresponding record for this reference.
    38. 38
      Baillie, S. E.; Clegg, W.; García-Álvarez, P.; Hevia, E.; Kennedy, A. R.; Klett, J.; Russo, L. S. Structural Elucidation, and Diffusion-Ordered NMR Studies of Homoleptic Alkyllithium Magnesiates: Donor-Controlled Structural Variations in Mixed-Metal Chemistry. Organometallics 2012, 31 (14), 5131– 5142
      38
      Synthesis, Structural Elucidation, and Diffusion-Ordered NMR Studies of Homoleptic Alkyllithium Magnesiates: Donor-Controlled Structural Variations in Mixed-Metal Chemistry
      Baillie, Sharon E.; Clegg, William; Garcia-Alvarez, Pablo; Hevia, Eva; Kennedy, Alan R.; Klett, Jan; Russo, Luca
      Organometallics (2012), 31 (14), 5131-5142CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
      This paper presents the synthesis and characterization of new homoleptic lithium magnesiate reagents incorporating the silyl-substituted alkyl ligand CH2SiMe3 in the presence of a variety of Lewis base donors, namely THF, 1,4-dioxane, N,N,N',N'-tetramethylethylenediamine (TMEDA), and N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA). The constitution of these bimetallic compds. has been assessed in both the solid state and soln. using a combination of x-ray crystallog. studies and multinuclear NMR spectroscopy, including 1H diffusion-ordered (1H-DOSY) NMR expts. These studies highlight the major role played by the donor mol. in controlling the structure of the complexes as well as the wide structural diversity available for these mixed-metal species ranging from discrete mols., as found for [(PMDETA)LiMg(CH2SiMe3)3] (6), to more complex supramol. arrangements, as in the 1D-polymeric chain [{(THF)LiMg(CH2SiMe3)3}∞] (2) or in the stoichiometrically distinct dioxane solvates [{(dioxane)2LiMgR3}∞] (3) and [{(dioxane)Li2Mg2R6}∞] (4). Furthermore, these studies have also revealed that in some cases the donor mol. can promote a redistribution process, as shown for the reaction of triorganomagnesiate [LiMg(CH2SiMe3)3] (1) with 1 molar equiv. of TMEDA, which led to the formation of lithium-rich tetraorganomagnesiate [(TMEDA)Li2Mg(CH2SiMe3)4] (5) along with Mg(CH2SiMe3)2. The formation of the unprecedented cationic lithium magnesiate [{(PMDETA)2Li2Mg(CH2SiMe3)3}+{Mg3(CH2SiMe3)6(OCH2SiMe3)}-] (7) is also described, by the controlled exposure to oxygen of the monomeric compd. [(PMDETA)LiMg(CH2SiMe3)3] (6).
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    39. 39
      Armstrong, D. R.; Emerson, H. S.; Hernán-Gómez, A.; Kennedy, A. R.; Hevia, E. New Supramolecular Assemblies in Heterobimetallic Chemistry: Synthesis of a Homologous Series of Unsolvated Alkali-Metal Zincates. Dalton Trans. 2014, 43 (38), 14229– 14238,  DOI: 10.1039/C4DT01131G
      There is no corresponding record for this reference.
    40. 40
      Uzelac, M.; Borilovic, I.; Amores, M.; Cadenbach, T.; Kennedy, A. R.; Aromí, G.; Hevia, E. Structural and Magnetic Diversity in Alkali-Metal Manganate Chemistry: Evaluating Donor and Alkali-Metal Effects in Co-Complexation Processes. Chem.─Eur. J. 2016, 22 (14), 4843– 4854,  DOI: 10.1002/chem.201504956
      There is no corresponding record for this reference.
    41. 41
      Hong, S.; Marks, T. J. Organolanthanide-Catalyzed Hydroamination. Acc. Chem. Res. 2004, 37 (9), 673– 686,  DOI: 10.1021/ar040051r
      41
      Organolanthanide-Catalyzed Hydroamination
      Hong, Sukwon; Marks, Tobin J.
      Accounts of Chemical Research (2004), 37 (9), 673-686CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
      A review; organolanthanides are highly efficient catalysts for inter- and intramol. hydroamination of various C-C unsaturations such as alkenes, alkynes, allenes, and dienes. Attractive features of organolanthanide catalysts include very high turnover frequencies and excellent stereoselectivities, rendering this methodol. applicable to concise synthesis of naturally occurring alkaloids and other polycyclic azacycles. The general hydroamination mechanism involves turnover-limiting C-C multiple bond insertion into the Ln-N bond, followed by rapid protonolysis by other amine substrates. Sterically less encumbered ligand designs have been developed to improve reaction rates, and metallocene and nonmetallocene chiral lanthanide complexes have been synthesized for enantioselective hydroamination.
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    42. 42
      Barrett, A. G. M.; Brinkmann, C.; Crimmin, M. R.; Hill, M. S.; Hunt, P.; Procopiou, P. A. Heavier Group 2 Metals and Intermolecular Hydroamination: A Computational and Synthetic Assessment. J. Am. Chem. Soc. 2009, 131 (36), 12906– 12907,  DOI: 10.1021/ja905615a
      42
      Heavier Group 2 Metals and Intermolecular Hydroamination: A Computational and Synthetic Assessment
      Barrett, Anthony G. M.; Brinkmann, Christine; Crimmin, Mark R.; Hill, Michael S.; Hunt, Patricia; Procopiou, Panayiotis A.
      Journal of the American Chemical Society (2009), 131 (36), 12906-12907CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      A d. functional theory assessment of the use of the group 2 elements Mg, Ca, Sr, and Ba for the intermol. hydroamination of ethene indicated that the efficiency of the catalysis is dependent upon both the polarity and the deformability of the electron d. within the metal-substituent bonds of key intermediates and transition states. The validity of this anal. was supplemented by a preliminary study of the use of group 2 amides for the intermol. hydroamination of vinyl arenes. Although strontium was found to provide the highest catalytic activity, in line with the expectation provided by the theor. study, a preliminary kinetic anal. demonstrated that this is possibly a consequence of the increased radius and accessibility of this cation rather than a reflection of a reduced barrier for rate-detg. alkene insertion.
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    43. 43
      Zhang, X.; Emge, T. J.; Hultzsch, K. C. A Chiral Phenoxyamine Magnesium Catalyst for the Enantioselective Hydroamination/Cyclization of Aminoalkenes and Intermolecular Hydroamination of Vinyl Arenes. Angew. Chem., Int. Ed. 2012, 51 (2), 394– 398,  DOI: 10.1002/anie.201105079
      There is no corresponding record for this reference.
    44. 44
      Liu, B.; Roisnel, T.; Carpentier, J.-F.; Sarazin, Y. When Bigger Is Better: Intermolecular Hydrofunctionalizations of Activated Alkenes Catalyzed by Heteroleptic Alkaline Earth Complexes. Angew. Chem., Int. Ed. 2012, 51 (20), 4943– 4946,  DOI: 10.1002/anie.201200364
      44
      When Bigger Is Better: Intermolecular Hydrofunctionalizations of Activated Alkenes Catalyzed by Heteroleptic Alkaline Earth Complexes
      Liu, Bo; Roisnel, Thierry; Carpentier, Jean-Francois; Sarazin, Yann
      Angewandte Chemie, International Edition (2012), 51 (20), 4943-4946, S4943/1-S4943/28CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      New alk.-earth amido complexes catalyze the regioselective intermol. hydroamination and hydrophosphination of styrene and isoprene with unprecedented activities. The catalytic performances increased linearly with the size of the metal.
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    45. 45
      Germain, S.; Lecoq, M.; Schulz, E.; Hannedouche, J. Lithium-Catalyzed Anti-Markovnikov Intermolecular Hydroamination Reactions of Vinylarenes and Simple Secondary Amines. ChemCatChem 2017, 9 (10), 1749– 1753,  DOI: 10.1002/cctc.201700043
      There is no corresponding record for this reference.
    46. 46
      Horrillo-Martínez, P.; Hultzsch, K. C.; Gil, A.; Branchadell, V. Base-Catalyzed Anti-Markovnikov Hydroamination of Vinylarenes – Scope, Limitations and Computational Studies. Eur. J. Org Chem. 2007, 2007, 3311– 3325,  DOI: 10.1002/ejoc.200700147
      There is no corresponding record for this reference.
    47. 47
      Kumar, K.; Michalik, D.; Garcia Castro, I.; Tillack, A.; Zapf, A.; Arlt, M.; Heinrich, T.; Boettcher, H.; Beller, M. Biologically Active Compounds through Catalysis: Efficient Synthesis of N-(Heteroarylcarbonyl)-N′-(Arylalkyl)Piperazines. Chem.─Eur. J. 2004, 35 (24), 746– 757,  DOI: 10.1002/chin.200424144
      There is no corresponding record for this reference.
    48. 48

      For an Example of Incomplete Transamidation with NaFe(HMDS)3; see Ref (33). For Stoichiometric Experiments of NaFe(HMDS)3 with Piperidine; see Supporting Information.

      There is no corresponding record for this reference.
    49. 49
      Mulks, F. F.; Bole, L. J.; Davin, L.; Hernán-Gómez, A.; Kennedy, A.; García-Álvarez, J.; Hevia, E. Ambient Moisture Accelerates Hydroamination Reactions of Vinylarenes with Alkali-Metal Amides under Air. Angew. Chem., Int. Ed. 2020, 59 (43), 19021– 19026,  DOI: 10.1002/anie.202008512
      There is no corresponding record for this reference.
    50. 50
      Hujon, F.; Lyngdoh, R. H. D.; King, R. B. Iron-Iron Bond Lengths and Bond Orders in Diiron Lantern-Type Complexes with High Spin Ground States. Eur. J. Inorg. Chem. 2021, 2021, 848– 860,  DOI: 10.1002/ejic.202000897
      50
      Iron-Iron Bond Lengths and Bond Orders in Diiron Lantern-Type Complexes with High Spin Ground States
      Hujon, Fitzerald; Lyngdoh, Richard H. Duncan; King, R. Bruce
      European Journal of Inorganic Chemistry (2021), 2021 (9), 848-860CODEN: EJICFO; ISSN:1434-1948. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Diiron paddlewheel- or lantern-type complexes comprise an interesting subclass of binuclear iron complexes, existing with digonal, trigonal, and tetragonal ligand arrays. Exptl. known members show Fe-Fe bonds of lengths ranging from 2.13 to 2.73 Å, with Fe-Fe bond orders ranging from 0.5 to 2. Truncated models for 30 exptl. characterized diiron paddlewheel-type complexes have been studied by DFT using the M06-L functional, reproducing the Fe-Fe bond lengths quite well. In addn., we use DFT to treat three series of model diiron complexes Fe2Lx (x = 2, 3, 4) in various low-lying spin states, L being the unsubstituted formamidinate, guanidinate, and formate ligands (along with a series of axially ligated formate complexes) in order to predict ground state spin multiplicities, Fe-Fe bond lengths, and features of the ligand arrays. The ground states all have high spin multiplicities (septets, octets, and nonets). Formal bond order (fBO) values are suggested for the Fe-Fe bonds in these 61 complexes using an electron bookkeeping procedure, in addn. to the Fe-Fe bond orders obtained by metal-metal MO anal. for ground state species. Fe-Fe bond orders up to 3 are noted in some excited states. Deviations from D3h and D4h symmetry are noted for many trigonal and tetragonal complexes, being attributed to inherent Jahn-Teller distortions. The formamidinate and guanidinate series show many similarities, while the formate series differs from these two in several aspects. From these results, ranges are derived for Fe-Fe bond lengths of orders 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0. The Fe-Fe bond length ranges for these non-carbonyl lantern complexes are found to be appreciably lower than the corresponding ranges for diiron complexes with carbonyl ligands as compiled earlier from computational and exptl. results.
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    51. 51
      Kuppuswamy, S.; Bezpalko, M. W.; Powers, T. M.; Turnbull, M. M.; Foxman, B. M.; Thomas, C. M. Utilization of Phosphinoamide Ligands in Homobimetallic Fe and Mn Complexes: The Effect of Disparate Coordination Environments on Metal–Metal Interactions and Magnetic and Redox Properties. Inorg. Chem. 2012, 51 (15), 8225– 8240,  DOI: 10.1021/ic300776y
      51
      Utilization of Phosphinoamide Ligands in Homobimetallic Fe and Mn Complexes: The Effect of Disparate Coordination Environments on Metal-Metal Interactions and Magnetic and Redox Properties
      Kuppuswamy, Subramaniam; Bezpalko, Mark W.; Powers, Tamara M.; Turnbull, Mark M.; Foxman, Bruce M.; Thomas, Christine M.
      Inorganic Chemistry (2012), 51 (15), 8225-8240CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      Homobimetallic phosphinoamide-bridged diiron and dimanganese complexes in which the two metals maintain different coordination environments were synthesized. Systematic variation of the steric and electronic properties of the phosphinoamide P and N substituents leads to structurally different complexes. Reaction of [iPrNKPPh2] (1) with MCl2 (M = Mn, Fe) affords the phosphinoamide-bridged bimetallic complexes [Mn(iPrNPPh2)3Mn(iPrNPPh2)] (3) and [Fe(iPrNPPh2)3Fe(iPrNPPh2)] (4). Complexes 3 and 4 are isostructural, with one metal center preferentially binding to the three amide ligands in a trigonal planar arrangement while the second metal center is ligated by three phosphine donors. A fourth phosphinoamide ligand caps the tetrahedral coordination sphere of the phosphine-ligated metal center. Mossbauer spectroscopy of complex 4 suggests that the metals in these complexes are best described as FeII centers. In contrast, treatment of MnCl2 or FeI2 with [MesNKPiPr2] (2) gives the halide-bridged species [(THF)Mn(μ-Cl)(MesNPiPr2)2Mn(MesNPiPr2)] (5) and [(THF)Fe(μ-I)(MesNPiPr2)2FeI] (7), resp. Use of FeCl2 in place of FeI2, however, leads exclusively to the C3-sym. complex [Fe(MesNPiPr2)3FeCl] (6), structurally similar to 4 but with a halide bound to the phosphine-ligated Fe center. The Mossbauer spectrum of 6 is also consistent with high spin FeII centers. Thus, in the case of the [iPrNPPh2]- and [MesNPiPr2]- ligands, zwitterionic complexes with the two metals in disparate coordination environments are preferentially formed. In the case of the more electron-rich ligand [iPrNPiPr2]-, complexes with a 2:1 mixed donor ligand arrangement, in which one of the ligand arms has reversed orientation relative to the previous examples, are formed exclusively when [iPrNLiPiPr2] (generated in situ) is treated with MCl2 (M = Mn, Fe): (THF)3LiCl[Mn(NiPrPiPr2)2(PiPr2NiPr)MnCl] (8) and [Fe(NiPrPiPr2)2(PiPr2NiPr)FeCl] (9). Bimetallic complexes 3-9 were structurally characterized using x-ray crystallog., revealing Fe-Fe interat. distances indicative of metal-metal bonding in complexes 6 and 9 (and perhaps 4, to a lesser extent). All of the complexes appear to adopt high spin electron configurations, and magnetic measurements indicate significant antiferromagnetic interactions in Mn2 complexes 5 and 8 and no discernible magnetic superexchange in Fe2 complex 4. The redox behavior of complexes 3-9 also was studied using cyclic voltammetry, and theor. studies (DFT) were performed to gain insight into the metal-metal interactions in these unique asym. complexes.
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  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsorginorgau.4c00066.

    • Experimental details, NMR spectra, and X-ray crystallog-raphy data General methods, synthesis of organometallic complexes, X-ray crystallographic data, stoichiometric reaction with NaFe(HMDS)3, catalytic reactions, cross-over experiment with I and morpholine, characterization of the products, and copies of NMR Spectra (PDF)

    Accession Codes

    Deposition Numbers 2376520–2376523 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via the joint Cambridge Crystallographic Data Centre (CCDC) and Fachinformationszentrum Karlsruhe Access Structures service.Accession Codes CCDC 2376520–2376523 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.


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