ACS Publications. Most Trusted. Most Cited. Most Read
Monodentate σ-Accepting Boron-Based Ligands Bearing Square-Planar Ni(0) Centers
More

OR SEARCH CITATIONS

My Activity
Publications

Figure 1Loading Img
Download Hi-Res ImageDownload to MS-PowerPointCite This:J. Am. Chem. Soc. 2025, 147, 10, 8326-8335
  • Open Access
Article

Monodentate σ-Accepting Boron-Based Ligands Bearing Square-Planar Ni(0) Centers
Click to copy article linkArticle link copied!

  • Yutaka Mondori
    Yutaka Mondori
    Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
    More by Yutaka Mondori
  • Yasuhiro Yamauchi
    Yasuhiro Yamauchi
    Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
    More by Yasuhiro Yamauchi
  • Takahiro Kawakita
    Takahiro Kawakita
    Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
    More by Takahiro Kawakita
  • Sensuke Ogoshi
    Sensuke Ogoshi
    Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
    More by Sensuke Ogoshi
    Orcidhttps://orcid.org/0000-0003-4188-8555
  • Yuta Uetake*
    Yuta Uetake
    Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
    Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University, Suita, Osaka 565-0871, Japan
    *Email: [email protected]
    More by Yuta Uetake
    Orcidhttps://orcid.org/0000-0002-4742-8085
  • Yasuo Takeichi
    Yasuo Takeichi
    Department of Applied Physics, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
    More by Yasuo Takeichi
    Orcidhttps://orcid.org/0000-0003-3334-0274
  • Hidehiro Sakurai
    Hidehiro Sakurai
    Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
    Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University, Suita, Osaka 565-0871, Japan
    More by Hidehiro Sakurai
    Orcidhttps://orcid.org/0000-0001-5783-4151
  • Yoichi Hoshimoto*
    Yoichi Hoshimoto
    Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
    Center for Future Innovation (CFi), Division of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
    *Email: [email protected]
    More by Yoichi Hoshimoto
    Orcidhttps://orcid.org/0000-0003-0882-6109
Open PDFSupporting Information (3)

Journal of the American Chemical Society

Cite this: J. Am. Chem. Soc. 2025, 147, 10, 8326–8335
Click to copy citationCitation copied!
https://doi.org/10.1021/jacs.4c15892
Published February 28, 2025

Copyright © 2025 The Authors. Published by American Chemical Society. This publication is licensed under

CC-BY-NC-ND 4.0 .

Abstract

Click to copy section linkSection link copied!
High Resolution Image
Download MS PowerPoint Slide

Transition metals are known to work as electron donors toward electron-accepting heavier-group-13 elements (Al, Ga, and In), called Z-type ligands. However, complexes with boron-based Z-type ligands are stable only in the presence of additional coordination units (the so-called “supported-ligand” strategy). Here, we report the synthesis and characterization of square-planar Ni(0) complexes that bear tris(perfluoroaryl)boranes as monodentate Z-type ligands, even though such coordination geometry has been traditionally associated with Ni(II) species based on the well-established ligand-field theory. A combined theoretical and experimental approach revealed a mixed covalent/dative character for the Ni–B bonds. This strategy uses frustrated L/Z-ligand pairs that combine sterically encumbered electron-donating (L-type) and electron-accepting ligands to form noncovalent interactions over L–M–Z units to achieve unprecedented low-valent transition metal species with monodentate Z-type ligands.

This publication is licensed under

CC-BY-NC-ND 4.0 .
  • cc licence
  • by licence
  • nc licence
  • nd licence
Copyright © 2025 The Authors. Published by American Chemical Society

Subjects

what are subjects

Introduction

Click to copy section linkSection link copied!
The concept of electron acceptors (i.e., Lewis acids; LAs) and donors (i.e., Lewis bases; LBs) has played a pivotal role in understanding chemical bonds between molecular fragments in various fields of chemistry (Figure 1a, top). (1) As a representative example, transition metal complexes, which are employed in the synthesis of pharmaceuticals, polymers, and commodities, (2,3) are constructed via the sharing of electrons between transition metals (TM) as LAs and ligands as LBs. Such TM ← LB interactions involve the transfer of electron(s) from an electron-occupied orbital (e.g., s, p, and their hybridized orbitals) in the LB to an empty d-orbital of TM (Figure 1a, middle); the arrow indicates the direction of the donor-to-acceptor-transfer of electrons. TM can simultaneously act as an electron donor via so-called back-donation when adequate orbital(s) in the ligands, such as antibonding σ* and π* orbitals, are available to accept electrons from the filled d-orbital in TM, leading to the formation of TM ⇄ LB bonds. (4) Additionally, electron donation from the filled d-orbitals in TM to empty p orbitals of main-group LAs (i.e., TM → LA) has also been known since the 1960s, although examples remain limited (Figure 1a, bottom). (5−10) These Lewis-acidic σ-accepting ligands are often referred to as Z-type ligands (formal two-electron acceptors) based on the number of electrons donated/accepted to/from TM, as proposed by Green (11) and Parkin, (9) while formal one- and two-electron donors are known as X- and L-types, respectively.

Figure 1

Figure 1. Concept of electron acceptors and donors. (a) A simplified representation of complexation between Lewis acids (LAs) and Lewis bases (LBs) and the related orbitals. (b) Coordination of transition metals (TM) to trivalent group-13 species. (c) Pioneering examples of Ni complexes that bear LnZ-type borane ligands. (d) A strategy for monodentate Z-type borane ligands based on frustrated L/Z-ligand pairs (this work).

High Resolution Image
Download MS PowerPoint Slide
Trivalent group-13 molecules, i.e., EX3 (E = B, Al, Ga, In), are typical LAs, as the empty p orbitals on the central E atom can accept electrons from various LBs, including main-group (12,13) and transition metals (Figure 1b). Since Burlitch, Hughes and co-workers crystallographically identified the presence of the Fe → Al bonding interaction in [Et4N][Fe(AlPh3)(cyclopentadienyl)(CO)2], (14) EX3 ligands have been employed as monodentate, unsupported Z-type ligands to accept electrons from a variety of transition metals. (5,7,10,15) However, the formation of the unsupported TM → BX3 interaction remains elusive due to the absence of crystallographical evidence, even though such a bonding situation has often been proposed based on experimental results using NMR and/or IR spectroscopy techniques. (5,7,16,17) In this context, Burlitch, Hughes, and co-workers proposed, based on IR and NMR analyses, the formation of Fe → BPh3 interactions after the reaction between [NEt4][(η5-cyclopentadienyl)Fe(CO)2] and BPh3; (17) however, even though the formation of a four-coordinated boron species was suggested, such spectroscopic analyses still remain questionable when discussing the existence of TM → BX3 interactions, as we demonstrate in this manuscript (see our results on e.g., 2a, 6a, and 7g). Remarkably, Campos and co-workers have recently reported that a Rh(I) complex bearing HB(C6F5)2 includes a bonding interaction between the Rh center and the B–H bond, and proposed that this complex may be potentially described as a transition metal complex bearing an unsupported borane ligand. (18) Based on our experience in custom-tailoring the Lewis acidity of triarylboranes (X = aryl) (19−21) and the report of Frenking (22) and co-workers, we are convinced that the striking differences in the reactivity of BX3 and its heavier analogues can be explained by the energetic penalty for the geometric deformation (Edef) from the trigonal-planar to the tetrahedral conformation via the formation of TM–EX3 bonds (Figure 1b). In fact, the Edef values for BX3 (X = halogen, alkyl, aryl) have been predicted to be at least twice those of the corresponding Al, Ga, and In analogues when triethylphosphine oxide was used as a model LB. (23) One strategy to compensate for this high Edef and to stabilize the tetrahedral TM–BX3 motif is the use of boranes that are equipped with additional L-type coordination units such as phosphines. In 1999, Hill and co-workers reported the synthesis and identification of several transition metal complexes that bear B(mt)3 (mt = 2-sulfanyl-1-methylimidazole) as a multidentate L3Z-type ligand. (24,25) However, these authors also pointed out the significant contribution of an imidazole-coordinated σ-boryl canonical form (an L2X2-type) of the B(mt)3 ligand; thus, a careful discussion of the nature of TM–borane bonds is required. (26,27) Later, Bourissou and co-workers successfully demonstrated that triarylboranes that bear di- or triphosphanyl moieties can serve as an adequate platform to construct supported TM–borane complexes (6) such as Ni/B-1 (28) (Figure 1c). Moreover, Ni/B-2 and Ni/B-3 have been synthesized by Emslie (29) and Peters, (30) respectively, and both have been proposed to include an η3-BCC coordination of an aryl borane unit to the nickel center. These pioneering results demonstrated that BX3 has sufficient electrophilicity to accept electrons donated from TM if the energetic penalty in the geometry deformation is effectively compensated. Nevertheless, an approach to successfully realize unsupported, monodentate Z-type borane ligands has remained elusive so far.
Herein, we report the synthesis of square-planar nickel(0) complexes that bear boranes as monodentate Z-type ligands via L-to-Z ligand substitution on the nickel(0) carbonyl complexes (Figure 1d). We found that the combination of sterically encumbered N-heterocyclic carbenes (NHCs) as L-type ligands and tris(perfluoroaryl)boranes (Bn) as Z-type ligands (i.e., frustrated L/Z-ligand pairs, named in analogy to the concept of frustrated Lewis pairs, FLPs) (31,32) is critical to generate these elusive species. The participation of multiple noncovalent interactions (NCI) over the NHC–TM–Bn units is discussed based on a systematic theoretical analysis.

Results and Discussion

Click to copy section linkSection link copied!
We have reported the formation of heterobimetallic Ni/Al complexes that bear N-phosphine-oxide-substituted imidazolinylidene L1 (Figure 2) as a bridging ligand via the Al(C6F5)3-induced rotation of the N-phosphinoyl moieties in (κ-C,O-L1)Ni(CO)2 (1a). (33) In the present study, we first attempted to extend this strategy, i.e., the Lewis acid-mediated reversible modulation of the local environment around the metal center, by exploring the reaction between 1a and B(C6F5)3 (B1), i.e., the boron analogue of Al(C6F5)3, with the expectation of forming the corresponding Ni/B bimetallic complex. However, upon dissociation of CO, we unexpectedly obtained (κ-C,O-L1)Ni(CO)(B1) (2a), which was isolated in 73% yield (Figure 2). In the 11B NMR spectrum of 2a in α,α,α-trifluorotoluene (TFT), the resonance of the B1 unit is observed at δB –10.3, which represents a significant upfield shift compared to that of free B1 (δB 59.9) and suggests the formation of a four-coordinated boron species. For comparison, complexes bearing phosphine-boranes such as Ni/B-1 display downfield-shifted resonances (δB 15–30), (28−30) highlighting the difference between the present unsupported Z-type systems and the hitherto reported supported systems. We have also isolated (κ-C,O-L2)Ni(CO)(B1) (2b) and (κ-C,O-L3)Ni(CO)(B1) (2c) in 71% and 48% yield, respectively, via L-to-Z ligand substitution. Under an inert-gas atmosphere at −30 °C, crystalline samples of 2a–2c are stable for at least several months. These complexes are nearly insoluble in nonpolar hydrocarbons such as n-pentane and n-hexane, slightly soluble in aromatic hydrocarbons such as benzene and toluene, and fully soluble in TFT. These nickel–borane complexes slowly decompose into unidentified products once dissolved in TFT (e.g., 2a: t1/2 = 615 min at 23 °C).

Figure 2

Figure 2. Reaction between Ni-carbonyl complexes and triarylboranes. The isolated yield is shown with the NMR yield in parentheses; N.R.: no reaction; Dipp: 2,6-diisopropylphenyl; Mes: mesityl.

High Resolution Image
Download MS PowerPoint Slide
To investigate which properties are essential to the ability of triarylboranes to induce the Ni → BAr3 interaction, we treated 1a with B(2,3,5,6-F4C6H)3 (B2) and B(2,6-F2C6H3)3 (B3); the Lewis acidity of these boranes decreases in the order B1 > B2 > B3 (for details of the Lewis acidity of B1–B5 toward Et3P═O, see Table S1). (34) Interestingly, (κ-C,O-L1)Ni(CO)(B2) (3a) was obtained in 71% yield; however, no reaction proceeded when B3 was employed, representing a plausible threshold of Lewis acidity below which the reactions between 1a and boranes cannot proceed. This hypothesis is consistent with the fact that no reaction occurred using B(C6Cl5)3 (B4), which exhibits lower Lewis acidity but higher electrophilicity than B1. (35) We then explored the effect of the ortho-F atoms in the B-aryl groups by using B(3,5-(CF3)2C6H3)3 (B5). B5 has been reported to exhibit higher Lewis acidity than B1 due to the electron-withdrawing nature of the meta-CF3 groups as well as the reduced intramolecular repulsion between ortho-H atoms in the tetrahedral four-coordinated boron unit. (36) Although a change in the NMR spectra was virtually negligible when 1a and B5 were mixed under ambient conditions, nickel complex 6a was isolated in 86% yield when the reaction mixture was stirred under reduced pressure to promote the removal of CO (Figure 2). Notably, in stark contrast to 2a–c and 3a, no resonance was observed in the 11B NMR spectrum of 6a. We therefore concluded that the corresponding Ni → B5 interaction does not manifest in this complex. Based on the results of the single-crystal X-ray diffraction (SC-XRD) and density functional theory (DFT) calculation analyses (vide infra), we concluded that in 6a, interactions between the Ni–CO bond and the boron atom, as well as between the Ni atom and one of the ipso-C atoms in the aryl group occur. Thus, B5 does not act as a typical Z-type ligand under the applied reaction conditions, although the observed bonding situations are nearly identical to those found in Ni/B-2 and Ni/B-3 (Figure S20). We subsequently used 6a as a precursor for preparing Ni–borane complexes via the borane–exchange reaction. The quantitative formation of 2a was confirmed when 6a was treated with B1. These results demonstrate the role of the ortho-F atoms of the Z-type tris(perfluoroaryl)borane ligands in the formation of the Ni → Bn interactions in 2a–2c and 3a.
Complexes 2a–c, 3a, and 6a were unambiguously characterized using SC-XRD analysis. Selected geometric parameters are summarized and compared with the reported parameters in Ni/B-1, Ni/B-2, and Ni/B-3 in Table S2. The molecular structures of 2a and 6a are shown in Figure 3a,b, respectively, together with a topological analysis of the electron density based on the atoms-in-molecules (AIM) theory. The Ni–B bond length in 2a (2.245(1) Å) falls within the expected bond-length range for supported TM–borane complexes (7) (ca. 2.05–2.90 Å) but is clearly longer than those in Ni/B-1 (2.168(2) Å) and Ni/B-3 (2.1543(9) Å). Notably, the interatomic distance between the Ni and B atoms in 6a (2.267(4) Å) is nearly identical to that in 2a, despite the fact that the NMR analyses of 6a do not support the formation of a four-coordinated boron species (vide supra). Furthermore, in the case of 2a, a bond critical point (BCP) was confirmed between the Ni and B atoms (electron density ρ = 0.07 [e × rBohr–3]; Laplacian of electron density ∇2ρ = 0.00 [e × rBohr–5]) (Figure 3a, bottom) in AIM analysis. These results suggest that the Ni–B bond in 2a possesses mixed covalent/dative bond properties. On the other hand, a corresponding BCP is not observed in 6a, again suggesting the absence of a significant Ni → B interaction (Figure 3b, bottom). These results suggest that the existence of TM → B bonding interactions should not be discussed based on the interatomic distance between the TM and B atoms. A natural bond orbital (NBO) analysis also highlights characteristic interactions involved in 2a (Figure S23). Donor–acceptor interactions between the Ni and B atoms (E(2) = +26.9 kcal mol–1) and carbonyl C2 and B atoms (E(2) = +57.6 kcal mol–1) were confirmed in 2a based on second-order-perturbation-theory analysis, suggesting a three-center four-electron bond among the Ni, B, and C2 atoms. It should also be noted here that the Ni → BX3 interaction can be interpreted in terms of a reversed bonding situation compared to the TM ← BLnX3–n (n = 1–2) interaction in borylene-coordinated transition metal complexes, wherein TMs and borylenes play the roles of LAs and LBs, respectively. (37,38)

Figure 3

Figure 3. Molecular structures and electron densities for (a) 2a and (b) 6a. Each structure was obtained from the corresponding SC-XRD analysis. The quantum theory of AIM bond paths (white lines) and bond critical points (BCPs, green dots) are also shown with overlaid contour plots of ∇2ρ (e × rBohr–5) through the plane defined by the C2, Ni, and B atoms (∇2ρ < 0 shown in blue; ∇2ρ > 0 shown in red). The AIM methods used the SCF electron density calculated at the PBE0-D3BJ/Def2-TZVPD//M06L/Def2-SVPD(Ni,O,F), Def2-SVP(others) level. Electron densities (ρ in e × rBohr–3) at selected BCPs are given. Values of ∇2ρ are also given in parentheses. Selected bond lengths (Å) for 2a: Ni–C1 1.976(1), Ni–C2 1.697(1), Ni–B 2.245(1), Ni–O1 1.9916(9), C2–O2 1.154(1), Ni···F 2.7450(9); 6a: Ni–C1 1.946(2), Ni–C2 1.735(3), Ni–B 2.267(4), Ni–C3 2.110(2), Ni···C4 2.238(2), Ni–O1 2.320(2), C2–B 2.373(4), C2–O2 1.146(3).

High Resolution Image
Download MS PowerPoint Slide
Although the AIM analysis does not support the existence of a BCP between the C2 and B atoms in 2a, the unusual topology of ∇2ρ between the C2 and B atoms (Figure 3a, bottom) is consistent with a partial contribution of the C2 → B electron transfer. Similarly, the corresponding C2 → B interaction (E(2) = +49.0 kcal mol–1) in 6a was also confirmed by the NBO analysis, while the Ni → B interaction (E(2) = +14.5 kcal mol–1) was found to be less significant (Figure S25). Based on these results, we conclude that the coordination of the Ni–C2 bond to the B atom is a key feature for understanding the connection between the Ni(Lm)(CO) and Bn (n = 1 and 5, m = 1–3) units, as seen in 6a. When ortho-F atoms are involved in Bn, the Ni → B interaction tends to become predominant, affording complexes 2a–c with monodentate Z-type borane ligands. Indeed, the AIM analysis confirmed the participation of an NCI between the Ni center and one of the ortho-F atoms in the B1 unit (interatomic Ni···F distance: 2.7450(9) Å; determined by SC-XRD). The corresponding Ni···F NCIs were also observed in 2c (2.688(49) Å) and 3a (2.642(62) Å), whereas 2b, which bears N-mesityl-substituted L2, can not be expected to include the interaction between Ni and F atoms (the distance between Ni and the nearest F atoms is 2.948(1) Å). Instead, one of the ipso-carbon atoms (Cip) in the B-C6F5 groups of 2b closely approaches the Ni center at 2.529(1) Å, which is, however, still longer than those found in Ni/B-2 (2.018(3) Å) (29) and Ni/B-3 (2.0750(7) Å). (30) A BCP is found between these two atoms in 2a (ρ = 0.02 [e × rBohr–3]; ∇2ρ = 0.09 [e × rBohr–5]; δ(Ni|F) = 0.10), suggesting that this Ni···F interaction is significantly weaker than e.g., Ni–O1 (ρ = 0.06 [e × rBohr–3]; ∇2ρ = 0.32 [e × rBohr–5]; δ(Ni|O1) = 0.34) and Ni–C1 (ρ = 0.11 [e × rBohr–3]; ∇2ρ = 0.34 [e × rBohr–5]; δ(Ni|C1) = 0.71) interactions, wherein δ(X|Y) values show the average number of electrons shared at a BCP between X and Y atoms. In addition, all ortho-F atoms in 2a are observed at nearly identical shifts in the 19F NMR analysis (δF –137 ∼ −122 at −28 °C), suggesting a labile and exchangeable nature of the Ni···F NCIs in solution. Moreover, multiple NCIs are simultaneously observed between the L1 and B1 ligands over the Ni atoms in 2a. We think that these NCIs are not individually essential for the stability of the Ni–borane complexes but rather work cooperatively with other weak interactions.
The geometry around the Ni centers in 2a–c and 3a was evaluated based on the value of τM [τM = {360 – (α + β)}/141 × β/α, where α and β are the largest and second-largest L–M–L angles obtained from their SC-XRD analyses]. (39) A τM value approaching 0 indicates that M adopts an ideal square-planar geometry, while a value approaching 1 corresponds to an ideal tetrahedral geometry. The Ni centers in 2a–c and 3a were found to adopt a distorted square-planar geometry with τNi values of 0.10–0.16, as has often been found for low-spin Ni(II) complexes; however, we eventually concluded that the electronic state of the Ni center in 2a would be close to Ni(0) (vide infra) (Figure 6). For the geometry around the boron center, as expected, distorted tetrahedral structures (τB = 0.7–0.8) were confirmed in 2a–c and 3a, while the B atom in 6a retains a rather planar geometry (sum of C–B–C angles = 353.8°, see also results of the tetrahedral characters [THC(B)] in Table S2).
To further confirm the prerequisite factors for the monodentate Z-type coordination of tris(perfluoroaryl)boranes, we carried out control experiments using B1 and nickel carbonyl complexes 1d–1f, which bear L4–L6 (Figure 4a); however, we did not observe the formation of the corresponding Ni–B1 complex under the applied conditions. In fact, the reaction between N-phosphanyl-substituted 1d and B1 resulted in the formation of (κ-C-L4)Ni(CO)3 in 19% yield through B1-induced disproportionation of the CO ligands in 1d, while other nickel carbonyl species were not identified by 31P and 19F NMR analyses. Thus, the N-phosphinoyl oxygen atom in L1 plays a role in stabilizing 2a as an isolable species. No reaction took place when 1e and 1f, which bear L5 and L6, respectively, were employed. We then turned our attention to 1g, which bears 1,3-di-tert-butylimidazol-2-ylidene L7, as it can generate an FLP species with B1 (Figure 4b). (40,41) We confirmed the generation of an equilibrium mixture including 1g (56%) and 7g (41%) at −30 °C after a period of 5 h. The characterization of 7g was accomplished based on NMR and SC-XRD analyses, which clearly confirmed the presence of the Ni(μ-η1,η2-CO)B unit. The resonance for the corresponding four-coordinated boron moiety was observed at δB –14.2 in the 11B NMR spectrum, a shift that is comparable to that reported for the four-coordinated boron complex [Cp2Ti(THF-d8)(μ-η1,η2-CO)B1] (42) (Cp = cyclopentadienyl) (δB –11). Complex 7g gradually decomposed even at −10 °C and eventually gave an unidentifiable mixture, probably via the dissociation of the end-on CO ligand. A crystal suitable for the SC-XRD analysis was prepared from this resultant mixture by recrystallization at −30 °C, and we confirmed the presence of binuclear nickel carbonyl complex 8g (Figure 4b). (43−46) Inspired by these results, we explored a possible mechanistic scenario for the formation of 7g from 1g and B1 based on DFT calculations at the PBE0-D3BJ/Def2-TZVPD//M06L/Def2-SVPD(Ni,F,O), Def2-SVP(others) level. The relative Gibbs free energies with respect to [1g + B1] (0.0 kcal mol–1) for selected molecules are shown in Figure 4b (for details, see Figure S29). We found that square-planar Ni complex 2g (+8.0 kcal mol–1), which bears B1 as a monodentate Z-type ligand, is formed via TS1′ (+11.9 kcal mol–1). While the Ni–B bond (2.43 Å) is longer than those in 2a–2c (ca. 2.2 Å), the BCP found between these atoms by the AIM analysis supports the presence of the Ni → B interaction in 2g (Figure S21). Moreover, as was seen for 2a, the participation of multiple NCIs between the L7 and B1 units in 2g was confirmed. Subsequently, the Ni-to-C2 migration of B1 proceeds via TS2′ (+23.9 kcal mol–1) to yield 7g (+1.6 kcal mol–1). These results imply that the use of multidentate carbene ligands (e.g., L1–L3) that can generate FLP species with tris(perfluoroaryl)boranes represents a strategy for generating transition metal complexes that bear monodentate Z-type borane ligands.

Figure 4

Figure 4. Effect of ligands. (a) Reaction with 1d–1f. (b) Reaction with 1g. The conversion of 1g through the transformation of 7g is shown in square brackets. The gas-phase optimized structure of 2g and the SC-XRD structure of 7g (except hydrogen atoms; thermal ellipsoids at 30% probability) are also shown. Selected bond lengths (Å) for 2g: Ni–C1 2.00, Ni–C2 1.82, Ni–B 2.43, C2–O 1.15; 7g: Ni–C1 1.976(4), Ni–O 1.966(3), Ni–C2 1.843(4), C2–O 1.207(5), C2–B 1.639(5).

High Resolution Image
Download MS PowerPoint Slide
Based on the results obtained up to this point, we considered possible reaction mechanisms to afford 2a from 1a and B1. Figure 5 depicts two selected paths with key intermediates and transition states (for further details, see Figure S28). Following the generation of association complex Int1-v1 (+5.1 kcal mol–1) from 1a and B1, the formation of the C2–B bond proceeds via TSadd1 (+13.6 kcal mol–1) to afford Ni(μ-η1-CO)B species Int2-v1 (+7.1 kcal mol–1; C2–B 1.80 Å) (blue colored path). Subsequently, another CO ligand smoothly dissociates to yield Int3-v1 (+12.1 kcal mol–1) without a significant energy barrier, which eventually forms Int4-v1 (+5.1 kcal mol–1) via the complete removal of CO. Coordination of the Cip atom in the C6F5 unit stabilizes Int4-v1, and the B atom effectively approaches the Ni center (Ni···B 2.31 Å). The C2-to-Ni migration of the B atom subsequently occurs via TSmig1 (+7.0 kcal mol–1), resulting in the construction of the Ni–B bond (2.22 Å) together with the elongation of the C2···B distance to 2.41 Å from 1.78 Å in Int4-v1. This mechanistic scenario predicts the facile formation of 2a after mixing 1a and B1, as the reaction rate would be predominantly determined by the formation of the C2–B bond via TSadd1, i.e., with an energy barrier of only +13.6 kcal mol–1. In contrast, for B3 and B4, the corresponding paths to form the C2–B bond and dissociate another CO ligand should become energetically unfavorable due to their decreased Lewis acidity, which would explain why no reaction was observed with 1a (Figure 2). On the other hand, we also found that the formation of Ni(μ-η1,η2-CO)B species Int2-v4 (−1.6 kcal mol–1) from Int1-v1 via TSism1 (+14.4 kcal mol–1) can compete with the above pathway via TSadd1 (gray colored path). The geometric parameters around the Ni atom in Int2-v4 (e.g., Ni–C2 1.85 Å; Ni–O2 2.01 Å; C2–B 1.62 Å) are nearly identical to those in 7g (Figure 4b), which bears L4, although the phosphinoyl O1 weakly coordinates to Ni in Int2-v4. This weak coordination of the phosphinoyl moiety should prevent the formation of a Ni–borane complex that bears two CO ligands and the carbene in L1, as seen in the interconversion between 2g and 7g. It would be possible to yield 2a from Int2-v4 via the regeneration of Int1-v1 and then TSmig1 as a result of the change in the coordination mode of CO from a μ-η1,η2 to a μ-η1 fashion; the overall energy barrier in this case is +16.0 kcal mol–1. Conversely, the path directly connecting Int2-v4 and 2a is unfavorable due to the higher energy barrier to overcome TSmig2.

Figure 5

Figure 5. Plausible mechanisms for the formation of 2a. Relative Gibbs free energies (kcal mol–1) with respect to [1a + B1] (0.0 kcal mol–1) are shown, calculated at the PBE0-D3BJ/Def2-TZVPD//M06L/Def2-SVPD(Ni,F,O), Def2-SVP(others) level. Parts of the molecular structures for the selected compounds are also shown with selected bond lengths (Å).

High Resolution Image
Download MS PowerPoint Slide
As mentioned earlier, the Ni center in 2a–c and 3a adopts a distorted square-planar geometry, which represents a fingerprint of the Ni(II) configuration in classical ligand-field theory. However, several transition metal complexes that bear Z-type ligands have been found to adopt unusual electronic configurations different from those expected based on their geometry. (47−51) Thus, we employed Ni K- and L2,3-edge X-ray absorption spectroscopy (XAS) to gain insight into the electronic configuration of 2a. Given that transition metal K-edge XAS is sensitive to the ligand-field geometry rather than the electronic state, we synthesized (κ-C,O-L1)Ni(C6F5)2 (9), a low-spin square-planar nickel complex with the formal oxidation state +II, as a reference. The Ni K-edge X-ray absorption near edge structure (XANES) data are shown in Figure 6a. The absorption edge of 2a appeared at 8333 eV with the pre-edge peak at 8327 eV; these values were almost identical to those of 1a. In addition, the absorption edge of 9 appeared at 8336 eV, i.e., 3 eV higher than that of 2a. Considering the identical ligand-field geometries in 2a and 9, this edge-shift suggests that 2a adopts the formal electric state Ni(0). The Ni L2,3-edge XAS analysis afforded deeper insight, as the hole number in Ni 3d orbitals is proportional to the sum of the Ni L3- and Ni L2-edge peak area based on the sum rule. (52,53) To this end, Ni d-electron counts are inversely proportional to the sum of the Ni L3- and Ni L2-edge peak area, which allows transition metal L2,3-edge XAS to be used as a direct probe for d-electron occupancy. The Ni L2,3-edge XAS experiments were conducted using the total electron yield (TEY) method under vacuum conditions, and the obtained XAS data of the (κ-C,O-L1)Ni complexes 1a, 2a, 9, and 10 are shown in Figure 6b, together with those of Ni(COD)(DQ) (COD: 1,5-cyclooctadiene, DQ: duroquinone). (54) For the formal Ni(II) complexes 9 (low-spin) and 10 (high-spin), sharp and intense L3-edge peaks were observed at 856.6 and 854.8 eV, respectively. In contrast, Ni(COD)(DQ) exhibited a broadened first peak at 856.2 eV. A prominent second peak was detected at higher energy, which was ascribed to the Ni 2p → ligand transitions. (55) In the cases of 1a and 2a, the XAS signals are split into several peaks with low intensity, which was attributed to the influence of the electron-accepting ligands, such as carbonyl and borane. The Ni 3d electron counts were then calculated from the sum of the normalized peak area using the linear function established from the XAS data of the d-count calibrants [Et4N]2[NiCl4] and [Na(benzo-15-crown-5)]2[Ni(mnt)2] (mnt: 1,2-dicyano-ethene-1,2-dithiolate) (Figure 6c and Table S6). (56,57) The Ni 3d count of 2a (9.1) is comparable to those of the other formal Ni(0) complexes, such as 1a (9.0) and Ni(COD)(DQ) (9.0). These results are also consistent with the estimated electron configuration of (3d)9.10(4s)0.32 calculated by the NBO7 program.

Figure 6

Figure 6. Experimental and theoretical evaluation of the electronic state of the Ni complexes examined in this study. (a) Ni K-edge XAS spectra. (b) Ni L2,3-edge XAS spectra. (c) Sum-rule analysis. (d) A simplified Frontier-molecular-orbital energy diagram of 2a, focusing on the interaction between the Ni and B centers, calculated at PBE0-D3BJ/Def2-TZVPD level. (e) Kohn–Sham HOMO and LUMO+1 in 2a and their orbital composition.

High Resolution Image
Download MS PowerPoint Slide
Finally, we disclose the role of tris(perfluoroaryl)boranes that contain ortho-F atoms, such as B1 and B2, in constructing the unusual square-planar geometry at the Ni(0) center with the occupied 3d electron configuration (Figure 6d). Based on ligand-field theory, Ni(0) d10 complexes usually adopt a tetrahedral geometry; this tendency is clearly observed in 6a bearing ortho-protonated B5, which coordinates to the Ni center via the Cip (labeled as C3 in Figure 3b). On the other hand, in the case of the B1/B2 ligands, the repulsive effects generated between the Ni and ortho-F atoms would prohibit such coordination of the Cip atoms, and lead to orbital rehybridization to stabilize the high-lying occupied Ni 3dx2-y2 orbital with the assistance of σ-accepting B1/B2 ligands. As a result, 2a–c and 3a adopt sterically acceptable but electronically unfavorable square-planar geometries, i.e., the square-planar Ni d9.1 state, where the electron density on the Ni center is modulated through interactions with the supporting ligands. In fact, DFT calculations showed that the HOMO and LUMO+1 in 2a are predominantly located on the Ni–B bonds with significant contributions of the Ni 3d and B 2p atomic orbitals (HOMO: Ni 29.2% and B 15.5%; LUMO+1: Ni 15.1%, B 8.7%) (Figure 6e), supporting the conclusion that the Ni and B atoms form a typical Lewis base → acid interaction. Furthermore, an energy decomposition analysis (EDA) indicated a significant contribution of the electrostatic interaction (ΔEelstat) in the stabilization of the square-planar Ni centers bearing B1 and B2 (Table S4).

Conclusions

Click to copy section linkSection link copied!
In summary, we have isolated and fully characterized square-planar nickel carbonyl (Ni–CO) complexes that bear tris(perfluoroaryl)boranes as monodentate σ-accepting (Z-type) ligands. In these complexes, the Ni center exhibits a d9.1 configuration with a high-lying occupied 3dx2–y2 orbital, which is effectively stabilized by the σ-accepting ability of tris(perfluoroaryl)boranes with ortho-F atoms. The Ni–B bonds in these complexes exhibit mixed covalent/dative character. In contrast, B(3,5-(CF3)2C6H3)3 afforded a tetrahedral nickel complex via Ni–CO bond coordination to the boron atom, highlighting the critical role of the ortho-F atoms in constructing square-planar nickel–borane complexes. Under the explored experimental and theoretical conditions, such nickel–borane complexes seem to be generated through the combination of sterically encumbered N-heterocyclic carbenes (L-type ligands) and tris(perfluoroaryl)boranes (Z-type ligands). In addition, we observed the participation of multiple noncovalent interactions over the L–Ni–Z units, which should support the deformed tetrahedral four-coordinated boron units. This work thus demonstrates a strategy, namely, the use of frustrated L/Z-ligand pairs, for the formation of a hitherto elusive class of low-valent transition metal complexes.

Supporting Information

Click to copy section linkSection link copied!

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacs.4c15892.

  • Full details pertaining to the experimental methods, identification of the compounds, and DFT calculations (PDF)

  • AIM analysis (XLSX)

  • DFT coordinate (XLSX)

Accession Codes

Deposition Numbers 2384752–2384760 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.

Terms & Conditions

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

Click to copy section linkSection link copied!
  • Corresponding Authors
    • Yuta Uetake - Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan;  Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University, Suita, Osaka 565-0871, Japan;  Orcidhttps://orcid.org/0000-0002-4742-8085;  Email: [email protected]
    • Yoichi Hoshimoto - Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan;  Center for Future Innovation (CFi), Division of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan;  Orcidhttps://orcid.org/0000-0003-0882-6109;  Email: [email protected]
  • Authors
    • Yutaka Mondori - Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
    • Yasuhiro Yamauchi - Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
    • Takahiro Kawakita - Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
    • Sensuke Ogoshi - Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan;  Orcidhttps://orcid.org/0000-0003-4188-8555
    • Yasuo Takeichi - Department of Applied Physics, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan;  Orcidhttps://orcid.org/0000-0003-3334-0274
    • Hidehiro Sakurai - Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan;  Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University, Suita, Osaka 565-0871, Japan;  Orcidhttps://orcid.org/0000-0001-5783-4151
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

Click to copy section linkSection link copied!

We are grateful to Daisuke Hashizume (RIKEN) for insightful discussions on the AIM analysis. Ni K-edge XAS measurements were performed at the BL14B2 beamline of SPring-8 under the approval of the Japan Synchrotron Radiation Research Institute (proposal numbers 2020A1871, 2021A1630, 2022A1767, and 2022A1784). Ni L2,3-edge XAS measurements were performed at the BL19B beamline of KEK under the approval of the Photon Factory Program Advisory Committee (proposal numbers 2022P013 and 2024G031), and at the BL4B beamline of the UVSOR Synchrotron Facility with the approval of the Institute for Molecular Science (proposal number 21-697). Parts of the theoretical calculations were performed using resources from the Research Center for Computational Science, Okazaki, Japan (24-IMS-C089). This project was supported by Grants-in-Aid for Transformative Research Area (A) Digitalization-driven Transformative Organic Synthesis (22H05363 to Y.H.); Green Catalysis Science for Renovating Transformation of Carbon-Based Resources (24H01851 to Y.U.); JSPS KAKENHI grant Scientific Research (C) (22K05095 to Y.U.); the JST FOREST Program (JPMJFR2222 to Y.H.); a JSPS Research Fellowship (to Y.Y.); and JST SPRING (to Y.M.).

References

Click to copy section linkSection link copied!

This article references 57 other publications.

  1. 1
    Jensen, W. B. The Lewis Acid-Base Definitions: A Status Report. Chem. Rev. 1978, 78, 1– 31,  DOI: 10.1021/cr60311a002
    Google Scholar
    1
    The Lewis acid-base definitions: a status report
    Jensen, William B.
    Chemical Reviews (Washington, DC, United States) (1978), 78 (1), 1-22CODEN: CHREAY; ISSN:0009-2665.
    A review dealing with the historical, theor., and interpretive aspects of the Lewis definitions. 156 Refs.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE1cXnvFykug%253D%253D&md5=bc7c4a756a3337a2d068496e457d4a95
  2. 2
    Crawley, M. L.; Trost, B. M. Applications of Transition Metal Catalysis in Drug Discovery and Development: An Industrial Perspective; John Wiley & Sons, 2012; . DOI: 10.1002/9781118309872 .
    Google Scholar
    There is no corresponding record for this reference.
  3. 3
    Striegler, S.; Rieger, B.; Kacker, S.; Baugh, L. S. Late Transition Metal Polymerization Catalysis; Wiley VCH, 2003.
    Google Scholar
    There is no corresponding record for this reference.
  4. 4
    Hartwig, J. F. Organotransition Metal Chemistry: From Bonding to Catalysis; University Science Books, 2010.
    Google Scholar
    There is no corresponding record for this reference.
  5. 5
    Braunschweig, H.; Dewhurst, R. D.; Schneider, A. Electron-Precise Coordination Modes of Boron-Centered Ligands. Chem. Rev. 2010, 110, 3924– 3957,  DOI: 10.1021/cr900333n
    Google Scholar
    5
    Electron-Precise Coordination Modes of Boron-Centered Ligands
    Braunschweig, Holger; Dewhurst, Rian D.; Schneider, Achim
    Chemical Reviews (Washington, DC, United States) (2010), 110 (7), 3924-3957CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review summarizes the chem. of mol. compds. featuring "electron precise" two center covalent and dative transition metal-boron interactions such as with the BR3 fragment (borane complexes), BR2 ligands (boryl complexes), B-R fragments as terminal or bridging ligands (borylene complexes) or lone boron atom as ligand (boride complexes).
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXjtlaitLw%253D&md5=ba4c8b6a5a537c5fb63c502461bdb090
  6. 6
    Amgoune, A.; Bourissou, D. σ-Acceptor, Z-type ligands for transition Metals. Chem. Commun. 2011, 47, 859– 871,  DOI: 10.1039/C0CC04109B
    Google Scholar
    6
    σ-Acceptor, Z-type ligands for transition metals
    Amgoune, Abderrahmane; Bourissou, Didier
    Chemical Communications (Cambridge, United Kingdom) (2011), 47 (3), 859-871CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    A review. The ability of Lewis acids to coordinate to transition metals as σ-acceptor ligands was recognized as early as in the 1970's, but so-called Z-type ligands remained curiosities until the early 2000's. Over the last decade, significant progress was made in this area, esp. via the incorporation of Lewis acid moieties into multidentate, ambiphilic ligands. The authors' understanding of the nature and influence of TM → Z interactions has considerably improved and the scope of Lewis acids susceptible to behave as σ-acceptor ligands was significantly extended. This feature article summarizes these recent achievements.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhsF2isrbN&md5=d886ffe6c81105043b4cba0784c0c2c0
  7. 7
    Braunschweig, H.; Dewhurst, R. D. Transition metals as Lewis bases: “Z-type” boron ligands and metal-to-boron dative bonding. Dalton Trans. 2011, 40, 549– 558,  DOI: 10.1039/C0DT01181A
    Google Scholar
    7
    Transition metals as Lewis bases: "Z-type" boron ligands and metal-to-boron dative bonding
    Braunschweig, Holger; Dewhurst, Rian D.
    Dalton Transactions (2011), 40 (3), 549-558CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
    A review. While the vast majority of inorg. chem. involves electron donation from main-group atoms to metals, an intriguing yet flip-side exists: where Lewis-basic metals donate electron d. to Lewis-acidic main-group atoms (most often boron). These so-called Z-type ligands, along with other less clear-cut complexes, are examples of this metal-ligand role reversal. This perspective article offers an introduction to metal-to-boron dative bonding, and attempts to correlate spectroscopic and structural data from the complexes.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhs1WjtbrI&md5=c394f11b5e719dbfe05e715cf4998f4f
  8. 8
    Bauer, J.; Braunschweig, H.; Dewhurst, R. D. Metal-Only Lewis Pairs with Transition Metal Lewis Bases. Chem. Rev. 2012, 112, 4329– 4346,  DOI: 10.1021/cr3000048
    Google Scholar
    8
    Metal-Only Lewis Pairs with Transition Metal Lewis Bases
    Bauer, Juergen; Braunschweig, Holger; Dewhurst, Rian D.
    Chemical Reviews (Washington, DC, United States) (2012), 112 (8), 4329-4346CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. The following topics are discussed:the history of metal-metal dative bond concept; complexes with d-block metal → s/p-Block metal dative bonding; complexes with d-block metal → d/f-Block metal dative bonding; bridged and other boredline cases: complexes with Groups 6, 7, 8, 9, and 10 metal bases.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XnsVeqsrk%253D&md5=92c3322a8d827d824f27c5fee76a66c3
  9. 9
    Parkin, G. Impact of the coordination of multiple Lewis acid functions on the electronic structure and vn configuration of a metal center. Dalton Trans. 2022, 51, 411– 427,  DOI: 10.1039/D1DT02921E
    Google Scholar
    9
    Impact of the coordination of multiple Lewis acid functions on the electronic structure and vn configuration of a metal center
    Parkin, Gerard
    Dalton Transactions (2022), 51 (2), 411-427CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
    The covalent bond classification (CBC) method represents a mol. as MLlXxZz by evaluating the total no. of L, X and Z functions interacting with M. The CBC method is a simplistic approach that is based on the notion that the bonding of a ligating atom (or group of atoms) can be expressed in terms of the no. of electrons it contributes to a 2-electron bond. In many cases, the bonding in a mol. of interest can be described in terms of a 2-center 2-electron bonding model and the MLlXxZz classification can be derived straightforwardly by considering each ligand independently. However, the bonding within a mol. cannot always be described satisfactorily by using a 2-center 2-electron model and, in such situations, the MLlXxZz classification requires a more detailed consideration than one in which each ligand is treated in an independent manner. The purpose of this article is to provide examples of how the MLlXxZz classification is obtained in the presence of multicenter bonding interactions. Specific emphasis is given to the treatment of multiple π-acceptor ligands and the impact on the vn configuration, i.e. the no. of formally nonbonding electrons on an element of interest.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXislynsL%252FI&md5=7370cc77c8ae2576eb270e0b49d0e066
  10. 10
    Komuro, T.; Nakajima, Y.; Takaya, J.; Hashimoto, H. Recent progress in transition metal complexes supported by multidentate ligands featuring group 13 and 14 elements as coordinating atoms. Coord. Chem. Rev. 2022, 473, 214837– 214864,  DOI: 10.1016/j.ccr.2022.214837
    Google Scholar
    10
    Recent progress in transition metal complexes supported by multidentate ligands featuring group 13 and 14 elements as coordinating atoms
    Komuro, Takashi; Nakajima, Yumiko; Takaya, Jun; Hashimoto, Hisako
    Coordination Chemistry Reviews (2022), 473 (), 214837CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
    Over the past decade, significant progress has been made in the chem. of transition metal complexes supported by multidentate chelate ligands, such as pincer-type ligands, in line with the development of active transition metal catalysts. This review summarizes recent progress in this area, with a focus on the incorporation of electropos. Group 13 (B, Al, Ga, and In) and Group 14 (Si and Ge) elements into the supporting multidentate ligands as coordinating atoms. These electropos. element-based ligands afford complexes with unique functionalities, such as remarkably strong σ-donor ability, high trans influence, and σ-acceptor ability, depending on the types of supporting ligands: L-type (2e donor), X-type (1e donor), and Z-type (2e acceptor) ligands. This review mainly covers the synthesis, fundamental properties, and catalysis of the complexes bearing these ligands.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XisFCjsLvO&md5=b40dc0b528963c1cdb61ea7e775e9cd8
  11. 11
    Green, M. L. H. A new approach to the formal classification of covalent compounds of the elements. J. Organomet. Chem. 1995, 500, 127– 148,  DOI: 10.1016/0022-328X(95)00508-N
    Google Scholar
    11
    A new approach to the formal classification of covalent compounds of the elements
    Green, M. L. H.
    Journal of Organometallic Chemistry (1995), 500 (1-2), 127-48CODEN: JORCAI; ISSN:0022-328X. (Elsevier)
    A new approach to the classification of covalent compds. of the transition metals is presented. The classification introduces the concepts of valency no. and ligand bond no. as alternatives to the concepts of formal oxidn. state and coordination no. Population d. maps (MLX plots) which represent the covalent compds. of an element as a function of all the known ligands are exemplified for chromium; molybdenum and tungsten; and nickel, palladium and platinum. These plots are used to identify the major characteristic chem. properties of the elements including reactivity trends and reaction mechanisms.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXotlektr8%253D&md5=c0a64ae93f1ebb8fb9c77e03007833df
  12. 12
    Davydova, E. I.; Sevastianova, T. N.; Timoshkin, A. Y. Molecular complexes of group 13 element trihalides, pentafluorophenyl derivatives and Lewis superacids. Coord. Chem. Rev. 2015, 297, 91– 126,  DOI: 10.1016/j.ccr.2015.02.019
    Google Scholar
    There is no corresponding record for this reference.
  13. 13
    Cowley, A. H. From group 13–group 13 donor–acceptor bonds to triple-decker cations. Chem. Commun. 2004, 2369– 2375,  DOI: 10.1039/B409497M
    Google Scholar
    There is no corresponding record for this reference.
  14. 14
    Burlitch, J. M.; Leonowicz, M. E.; Petersen, R. B.; Hughes, R. E. Coordination of Metal Carbonyl Anions to Triphenylaluminum, -gallium, and -indium and the Crystal Structure of Tetraethylammonium Triphenyl((η5-Cyclopentadienyl)dicarbonyliron)aluminate(Fe–Al). Inorg. Chem. 1979, 18, 1097– 1105,  DOI: 10.1021/ic50194a040
    Google Scholar
    There is no corresponding record for this reference.
  15. 15
    Kameo, H.; Nakazawa, H. Saturated Heavier Group 14 Compounds as σ-Electron-Acceptor (Z-type) Ligands. Chem. Rec. 2017, 17, 268– 286,  DOI: 10.1002/tcr.201600061
    Google Scholar
    15
    Saturated Heavier Group 14 Compounds as σ-Electron-Acceptor (Z-Type) Ligands
    Kameo, Hajime; Nakazawa, Hiroshi
    Chemical Record (2017), 17 (3), 268-286CODEN: CRHEAK; ISSN:1528-0691. (Wiley-VCH Verlag GmbH & Co. KGaA)
    This review article describes the chem. of transition-metal complexes contg. heavier group 14 elements (Si, Ge, and Sn) as the σ-electron-acceptor (Z-type) ligands and discusses the characteristics of bonds between the transition metal and Z-type ligand. Moreover, we review the iridium hydride mediated cleavage of E-X bonds (E = Si, Ge; X = F, Cl), where the key intermediates are pentacoordinate silicon or germanium compds. bearing a dative M→E bond.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xht12ns7jF&md5=48c6e933a5b2d619e464e78950e7582c
  16. 16
    For examples including Pt-complexes, see:Bauer, J.; Braunschweig, H.; Dewhurst, R. D.; Radacki, K. Reactivity of Lewis Basic Platinum Complexes Towards Fluoroboranes. Chem.─Eur. J. 2013, 19, 8797– 8805,  DOI: 10.1002/chem.201301056
    Google Scholar
    16
    Reactivity of Lewis Basic Platinum Complexes Towards Fluoroboranes
    Bauer, Juergen; Braunschweig, Holger; Dewhurst, Rian D.; Radacki, Krzysztof
    Chemistry - A European Journal (2013), 19 (27), 8797-8805CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The interaction of Lewis acidic fluoroboranes, for example BF2Pf (Pf = perfluorophenyl) and BF2ArF (ArF = 3,5-bis(trifluoromethyl)phenyl), with Lewis basic Pt complexes such as [Pt(PEt3)3] and [Pt(PCy3)2] (Cy = cyclohexyl) is reported. Two presumed Lewis adducts could be identified in soln. and corresponding secondary products of these Lewis adducts were characterized in the solid state. Also, the concept of frustrated Lewis pairs (FLP) was applied to the activation of ethene in the system [Pt(BPf3)(CH2CH2)(dcpp)] (dcpp = 1,3-bis(dicyclohexylphosphino)propane; Pf = perfluorophenyl). Finally, DFT calcns. were performed to det. the interaction between the Pt-centered Lewis bases and the B-centered Lewis acids. Addnl., several possible mechanisms for the oxidative addn. of the boranes BF3, BCl3, and BF2ArF to the model complex [Pt(PMe3)2] are presented.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXnvVKqtLw%253D&md5=f78b83c2868637ada6f5dc794f96afe8
  17. 17
    For examples including Fe-complexes, see:Burlitch, J. M.; Burk, J. H.; Leonowicz, M. E.; Hughes, R. E. Migration of triphenylboron from iron to a geminal η5-cylopentadienyl ligand. Inorg. Chem. 1979, 18, 1702– 1709,  DOI: 10.1021/ic50196a061
    Google Scholar
    There is no corresponding record for this reference.
  18. 18
    For examples including Rh-complexes, see:Alférez, M. G.; Moreno, J. J.; Gaona, M. A.; Maya, C.; Campos, J. Ligand Postsynthetic Functionalization with Fluorinated Boranes and Implications in Hydrogenation Catalysis. ACS Catal. 2023, 13, 16055– 16066,  DOI: 10.1021/acscatal.3c02764
    Google Scholar
    There is no corresponding record for this reference.
  19. 19
    Hashimoto, T.; Asada, T.; Ogoshi, S.; Hoshimoto, Y. Main group catalysis for H2 purification based on liquid organic hydrogen carriers. Sci. Adv. 2022, 8, eade0189  DOI: 10.1126/sciadv.ade0189
    Google Scholar
    There is no corresponding record for this reference.
  20. 20
    Sakuraba, M.; Morishita, T.; Hashimoto, T.; Ogoshi, S.; Hoshimoto, Y. Remote Back Strain: A Strategy for Modulating the Reactivity of Triarylboranes. Synlett 2023, 34, 2187– 2192,  DOI: 10.1055/a-2110-5359
    Google Scholar
    There is no corresponding record for this reference.
  21. 21
    Hisata, Y.; Washio, T.; Takizawa, S.; Ogoshi, S.; Hoshimoto, Y. In-silico-assisted derivatization of triarylboranes for the ccatalytic reductive functionalization of aniline-derived amino acids and peptides with H2. Nat. Commun. 2024, 15, 3708,  DOI: 10.1038/s41467-024-47984-0
    Google Scholar
    There is no corresponding record for this reference.
  22. 22
    Goedecke, C.; Hillebrecht, P.; Uhlemann, T.; Haunschild, R.; Frenking, G. The Dewar-Chatt-Duncanson model reversed: Bonding analysis of group-10 complexes [(PMe3)2M–EX3] (M = Ni, Pd, Pt; E = B, Al, Ga, In, Tl; X = H, F, Cl, Br, I). Can. J. Chem. 2009, 87, 1470– 1479,  DOI: 10.1139/V09-099
    Google Scholar
    There is no corresponding record for this reference.
  23. 23
    Erdmann, P.; Greb, L. What Distinguishes the Strength and the Effect of a Lewis Acid: Analysis of the Gutmann–Beckett Method. Angew. Chem., Int. Ed. 2022, 61, e202114550  DOI: 10.1002/anie.202114550
    Google Scholar
    23
    What Distinguishes the Strength and the Effect of a Lewis Acid: Analysis of the Gutmann-Beckett Method
    Erdmann, Philipp; Greb, Lutz
    Angewandte Chemie, International Edition (2022), 61 (4), e202114550CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    IUPAC defines Lewis acidity as the thermodn. tendency for Lewis pair formation. This strength property was recently specified as global Lewis acidity (gLA), and is gauged for example by the fluoride ion affinity. Exptl., Lewis acidity is usually evaluated by the effect on a bound mol., such as the induced 31P NMR shift of triethylphosphine oxide in the Gutmann-Beckett (GB) method. This type of scaling was called effective Lewis acidity (eLA). Unfortunately, gLA and eLA often correlate poorly, but a reason for this is unknown. Hence, the strength and the effect of a Lewis acid are two distinct properties, but they are often granted interchangeably. The present work analyzes thermodn., NMR specific, and London dispersion effects on GB nos. for 130 Lewis acids by theory and expt. The deformation energy of a Lewis acid is identified as the prime cause for the crit. deviation between gLA and eLA but its correction allows a unification for the first time.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXislOhurnK&md5=c5de4510156ba53802263200b0f57618
  24. 24
    For examples including Ru-complexes, see:Hill, A. F.; Owen, G. R.; White, A. J. P.; Williams, D. J. The Sting of the Scorpion: A Metallaboratrane. Angew. Chem., Int. Ed. 1999, 38, 2759– 2761,  DOI: 10.1002/(SICI)1521-3773(19990917)38:18<2759::AID-ANIE2759>3.0.CO;2-P
    Google Scholar
    24
    The sting of the scorpion: a metallaboratrane
    Hill, Anthony F.; Owen, Gareth R.; White, Andrew J. P.; Williams, David J.
    Angewandte Chemie, International Edition (1999), 38 (18), 2759-2761CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH)
    The novel ruthenaboratrane complex [Ru{B(mt)3}(CO)(PPh3)] (4, mt = 2-sulfanyl-1-methylimidazolyl) was prepd. from the reaction of [Ru(CH:CHCPh2OH)Cl(CO)(PPh3)2] with Na[HB(mt)3] and characterized spectroscopically and by x-ray crystallog. (4·2CHCl3: triclinic, space group P‾1, R1 = 0.049). The complex has a Ru→B bond of 2.161(5) Å, resulting in a tetrahedral geometry for boron, and ruthenium is octahedral. This complex is the first example of a poly(azolyl)borate ligand that undergoes B-H activation (stinging of the "scorpionate") to give this metallaboratrane structure.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXmtl2rsLs%253D&md5=be4d43e88a21b9fcdf2c57be74b390b2
  25. 25
    Hill, A. F. An Unambiguous Electron-Counting Notation for Metallaboratranes. Organometallics 2006, 25, 4741– 4743,  DOI: 10.1021/om0602512
    Google Scholar
    25
    An Unambiguous Electron-Counting Notation for Metallaboratranes
    Hill, Anthony F.
    Organometallics (2006), 25 (20), 4741-4743CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
    As the field of metalloboratranes develops, a spectrum of behavior for the M→B bond will emerge, involving different degrees of electron transfer from metal to the Lewis acid. A cohesive notation for indicating the overall no. of electrons assocd. with the metal and the M-B unit should therefore serve to preempt confusion that might arise from electron-counting formalisms based on the contradictory dictums. It is hoped that adoption of the recommended (M→B)n notation wherein the superscript no. (n) denotes the total no. of electrons assocd. with the metal d orbitals and M→B group, will help obviate such a situation. E.g., complex [Os(CO)(PPh3){B(mt)3}] should be denoted (Os→B)8.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XotlCmsbk%253D&md5=2b10fc4086ab34921044606402de3ff3
  26. 26
    For examples including Rh-complexes, see:Crossley, I. R.; Hill, A. F.; Willis, A. C. Metallaboratranes: Tris(methimazolyl)borane Complexes of Rhodium(I). Organometallics 2006, 25, 289– 299,  DOI: 10.1021/om050772+
    Google Scholar
    26
    Metallaboratranes: Tris(methimazolyl)borane Complexes of Rhodium(I)
    Crossley, Ian R.; Hill, Anthony F.; Willis, Anthony C.
    Organometallics (2006), 25 (1), 289-299CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
    The syntheses and reactivity of the first rhodaboratranes, [RhX(PPh3){B(mt)3}] (X = Cl, H) and [Rh(η4-C8H12){B(mt)3}]Cl, are described in detail together with preliminary investigations of the mechanistic processes involved. The subsequent exploitation and circumvention of the lability of [RhCl(PPh3){B(mt)3}] in the synthesis of a range of isonitrile, [Rh(CNR)(PPh3){B(mt)3}]Cl (R = tBu, C6H3Me2-2,6, C6H2Me3-2,4,6), phosphine, [Rh(PMe3)n(PPh3)2-n{B(mt)3}]Cl (n = 0, 1, 2), and dialkyldithiocarbamate, [Rh(S2NEt2){B(mt)3}]Cl, complexes is described, along with the attempted synthesis of [Rh(CNtBu)2{B(mt)3}]Cl from [Rh(η4-C8H12){B(mt)3}]Cl. Single-crystal x-ray structure detns. of [Rh(L)(L'){B(mt)3}]Cl (L = CNtBu, CN(C6H3Me2-2,6), L' = PPh3; L = L' = PMe3) are reported.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXht1GmsLrL&md5=c308e273d26e859eb203f8aa51ae53ba
  27. 27
    Parkin, G. A. Simple Description of the Bonding in Transition-Metal Borane Complexes. Organometallics 2006, 25, 4744– 4747,  DOI: 10.1021/om060580u
    Google Scholar
    27
    A Simple Description of the Bonding in Transition-Metal Borane Complexes
    Parkin, Gerard
    Organometallics (2006), 25 (20), 4744-4747CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
    A review of nomenclature of the description of the bonding in transition-metal borane complexes.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XotlCmtr8%253D&md5=4d380ad53937c1634aef2c8878dbabf0
  28. 28
    For examples including Ni-, Cu-, Pd-, Ag-, Pt- and Au-complexes, see:Sircoglou, M.; Bontemps, S.; Bouhadir, G.; Saffon, N.; Miqueu, K.; Gu, W.; Mercy, M.; Chen, C.-H.; Foxman, B. M.; Maron, L.; Ozerov, O. V.; Bourissou, D. Group 10 and 11 Metal Boratranes (Ni, Pd, Pt, CuCl, AgCl, AuCl, and Au+) Derived from a Triphosphine–Borane. J. Am. Chem. Soc. 2008, 130, 16729– 16738,  DOI: 10.1021/ja8070072
    Google Scholar
    28
    Group 10 and 11 Metal Boratranes (Ni, Pd, Pt, CuCl, AgCl, AuCl, and Au+) Derived from a Triphosphine-Borane
    Sircoglou, Marie; Bontemps, Sebastien; Bouhadir, Ghenwa; Saffon, Nathalie; Miqueu, Karinne; Gu, Weixing; Mercy, Maxime; Chen, Chun-Hsing; Foxman, Bruce M.; Maron, Laurent; Ozerov, Oleg V.; Bourissou, Didier
    Journal of the American Chemical Society (2008), 130 (49), 16729-16738CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The ambiphilic triphosphine-borane ligand TPB (1, [o-iPr2P-C6H4]3B) readily coordinates to all Group 10 and 11 metals to afford a complete series of metal boratranes (TPB)[M] 2-8 (2: M = Ni, 3: M = Pd, 4: M = Pt, 5: M = CuCl, 6: M = AgCl, 7: M = AuCl, 8: M = Au+). Spectroscopic and structural characterization unambiguously establishes M→B interactions in all of these complexes. The 1st evidence for borane coordination to copper and silver is provided, and the Au→B interaction persists upon chloride abstraction. Exptl. and theor. considerations indicate that the M→B interaction is strongest in the Pt and Au complexes. The influence of the oxidn. state and charge of the metal is substantiated, and the consequences of relativistic effects are discussed. The coordination of the σ-acceptor borane ligand is found to induce a significant bathochromic shift of the UV-visible spectra, the Ni, Pd, and Pt complex presenting strong absorptions in the visible range. All of the group 10 and 11 metal boratranes adopt C3 symmetry both in the solid state and in soln. The central M→B interaction moderately influences the degree of helicity and configurational stability of these three-bladed propellers, and DFT calcns. support a dissociative pathway for the inversion process.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtlOlt7rN&md5=6309b00f4e0dd3ff44c1c9cc526c92f3
  29. 29
    For examples including Ni- and Pd-complexes, see:Emslie, D. J. H.; Harrington, L. E.; Jenkins, H. A.; Robertson, C. M.; Britten, J. F. Group 10 Transition-Metal Complexes of an Ambiphilic PSB-Ligand: Investigations into η3(BCC)-Triarylborane Coordination. Organometallics 2008, 27, 5317– 5325,  DOI: 10.1021/om800670e
    Google Scholar
    29
    Group 10 Transition-Metal Complexes of an Ambiphilic PSB-Ligand: Investigations into η3(BCC)-Triarylborane Coordination
    Emslie, David J. H.; Harrington, Laura E.; Jenkins, Hilary A.; Robertson, Craig M.; Britten, James F.
    Organometallics (2008), 27 (20), 5317-5325CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
    Reaction of 2,7-di-tert-butyl-5-diphenylboryl-4-diphenylphosphino-9,9-dimethylthioxanthene (TXPB) with [PdCl2(COD)] (COD = 1,5-cyclooctadiene) gave [PdCl(μ-Cl)(TXPB)] (3, 87% yield), which can be reduced in a stepwise fashion, forming [Pd(TXPB)] (2, 63%) via [{PdI(μ-Cl)(TXPB)}2] (4). Dinuclear 4 could also be prepd. through a comproportionation reaction of Pd(II) complex [PdCl(μ-Cl)(TXPB)] (3) with either [Pd(TXPB)] (2) or [Pd(dba)(TXPB)] (5, dba = dibenzylideneacetone). In complexes 3 and 4, the TXPB ligand is bound to Pd via the phosphine and thioether donors, with a chloride anion bridging between the metal and the borane unit of TXPB. By contrast, the TXPB ligand in 2 is bound to Pd not only via the phosphine and thioether donors but also through a Pd-(η3-BAr3) linkage involving B and the ipso- and ortho-C atoms of one B-Ph ring. The analogous Ni complex, [Ni(TXPB)] (6, 70%) also proved accessible by direct reaction of [Ni(COD)2] with TXPB. In both 2 and 6, short distances (2.02-2.33 Å) between the metal and the B-Cipso-Cortho unit of TXPB and 11B NMR signals shifted 38-39 ppm to lower frequency of free TXPB confirm the presence of a strong M-{η3(BCC)-BAr3} interaction. Reaction of either [Pd2(dvds)3] (dvds = 1,3-divinyltetramethyldisiloxane) with TXPB or complex 2 with dvds resulted in rapid formation of [(κ1-TXPB)Pd(η2:η2-dvds)] (7). The Pt analog of complex 7, [(κ1-TXPB)Pt(η2:η2-dvds)] (8, 59%), was also prepd. by reaction of [Pt(COD)2] with dvds, followed by TXPB. In both 7 and 8, the metal is trigonal planar as a result of η2:η2-coordination to dvds and bonding only to the phosphine group of TXPB. To assess the potential for a ligand with the same structural characteristics as TXPB to coordinate via three η1-interactions, the phosphine analog of TXPB; 2,7-di-tert-butyl-4,5-bis(diphenylphosphino)-9,9-dimethylthioxanthene (Thioxantphos) was prepd., and reaction with [PtX2(COD)] (X = Cl, I) resulted in the clean formation of [PtX(Thioxantphos)]X where X = Cl (9, 66%) and I (10, 72%). These complexes are square planar with the Thioxantphos ligand coordinated through three η1-interactions, confirming the steric accessibility of more traditional κ3-coordination in 4,5-disubstituted thioxanthene ligands such as Thioxantphos and TXPB.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtFaitLrF&md5=2e79a463d7ad27b8e01acf7215cf98a7
  30. 30
    For examples including Ni-complexes, see:Harman, W. H.; Peters, J. C. Reversible H2 Addition across a Nickel-Borane Unit as a Promising Strategy for Catalysis. J. Am. Chem. Soc. 2012, 134, 5080– 5082,  DOI: 10.1021/ja211419t
    Google Scholar
    30
    Reversible H2 Addition across a Nickel-Borane Unit as a Promising Strategy for Catalysis
    Harman, W. Hill; Peters, Jonas C.
    Journal of the American Chemical Society (2012), 134 (11), 5080-5082CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The synthesis and characterization of Ni complexes of the chelating diphosphine-borane ligands ArB(o-Ph2PC6H4)2 ([ArDPBPh]; Ar = Ph, Mes) is reported. The [ArDPBPh] framework supports pseudo-tetrahedral Ni complexes featuring η2-B,C coordination from the ligand backbone. For the B-Ph deriv., the THF adduct [PhDPBPh]Ni(THF) was characterized by x-ray diffraction and features a very short interaction between Ni and the η2-B,C ligand. For the B-mesityl deriv., the reduced Ni complex [MesDPBPh]Ni is isolated as a pseudo-three-coordinate naked species that undergoes reversible, nearly thermoneutral oxidative addn. of dihydrogen to give a borohydrido-hydride complex of Ni(II) which was characterized in soln. by multinuclear NMR. Also, [MesDPBPh]Ni is an efficient catalyst for the hydrogenation of olefin substrates under mild conditions.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XjtVCqt74%253D&md5=d450313692cf4ae0640e27f9ef688fa1
  31. 31
    Stephan, D. W.; Erker, G. Frustrated Lewis Pair Chemistry: Development and Perspectives. Angew. Chem., Int. Ed. 2015, 54, 6400– 6441,  DOI: 10.1002/anie.201409800
    Google Scholar
    31
    Frustrated Lewis Pair Chemistry: Development and Perspectives
    Stephan, Douglas W.; Erker, Gerhard
    Angewandte Chemie, International Edition (2015), 54 (22), 6400-6441CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. Frustrated Lewis pairs (FLPs) are combinations of Lewis acids and Lewis bases in soln. that are deterred from strong adduct formation by steric and/or electronic factors. This opens pathways to novel cooperative reactions with added substrates. Small-mol. binding and activation by FLPs has led to the discovery of a variety of new reactions through unprecedented pathways. Hydrogen activation and subsequent manipulation in metal-free catalytic hydrogenations is a frequently obsd. feature of many FLPs. The current state of this young but rapidly expanding field is outlined in this Review and the future directions for its broadening sphere of impact are considered.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXotlGks7g%253D&md5=41885ca09b81140d5c5fc2b6a75f2fe7
  32. 32
    Jupp, A. R.; Stephan, D. W. New Directions for Frustrated Lewis Pair Chemistry. Trends Chem. 2019, 1, 35– 48,  DOI: 10.1016/j.trechm.2019.01.006
    Google Scholar
    32
    New Directions for Frustrated Lewis Pair Chemistry
    Jupp, Andrew R.; Stephan, Douglas W.
    Trends in Chemistry (2019), 1 (1), 35-48CODEN: TCRHBQ; ISSN:2589-5974. (Cell Press)
    A review. The concerted action of a Lewis acid and base can activate H2 and other small mols. Such frustrated Lewis pairs (FLPs) have garnered much attention and prompted many investigations into the activation of small mols. and catalysis. Although the nature, mechanism of action, and range of FLP systems continues to expand, this concept has also inspired ever-widening chem. Applications in hydrogenation and polymn. catalysis, as well as in synthetic chem., have provided selective processes and metal-free protocols. Heterogeneous FLP catalysts are emerging, and polymeric FLPs offer avenues to unique materials and strategies for sensing and carbon capture. The prospects for further impact of this remarkably simple reaction paradigm are considered.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXit1CqtL%252FP&md5=76c0325cb884a2be4d09dd97a64c8acd
  33. 33
    Yamauchi, Y.; Mondori, Y.; Uetake, Y.; Takeichi, Y.; Kawakita, T.; Sakurai, H.; Ogoshi, S.; Hoshimoto, Y. Reversible Modulation of the Electronic and Spatial Environment around Ni(0) Centers Bearing Multifunctional Carbene Ligands with Triarylaluminum. J. Am. Chem. Soc. 2023, 145, 16938– 16947,  DOI: 10.1021/jacs.3c06267
    Google Scholar
    33
    Reversible Modulation of the Electronic and Spatial Environment around Ni(0) Centers Bearing Multifunctional Carbene Ligands with Triarylaluminum
    Yamauchi, Yasuhiro; Mondori, Yutaka; Uetake, Yuta; Takeichi, Yasuo; Kawakita, Takahiro; Sakurai, Hidehiro; Ogoshi, Sensuke; Hoshimoto, Yoichi
    Journal of the American Chemical Society (2023), 145 (30), 16938-16947CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Designing and modulating the electronic and spatial environments surrounding metal centers is a crucial issue in a wide range of chem. fields that use organometallic compds. Herein, the authors demonstrate a Lewis-acid-mediated reversible expansion, contraction, and transformation of the spatial environment surrounding Ni(0) centers that bear N-phosphine oxide-substituted N-heterocyclic carbenes (henceforth referred to as (S)PoxIms). Reaction between tetrahedral (syn-κ-C,O-(S)PoxIm)Ni(CO)2 and Al(C6F5)3 smoothly afforded heterobimetallic Ni/Al species such as trigonal-planar {κ-C-Ni(CO)2}(μ-anti-(S)PoxIm){κ-O-Al(C6F5)3} via a complexation-induced rotation of the N-phosphine oxide moieties, while the addn. of 4-dimethylaminopyridine resulted in the quant. regeneration of the former Ni complexes. The corresponding interconversion also occurred between (SPoxIm)Ni(η2:η2-diphenyldivinylsilane) and {κ-C-Ni(η2:η2-diene)}(μ-anti-SPoxIm){κ-O-Al(C6F5)3} via the coordination and dissocn. of Al(C6F5)3. The shape and size of the space around the Ni(0) center was drastically changed through this Lewis-acid-mediated interconversion. Also, the multinuclear NMR, IR, and XAS analyses of the aforementioned carbonyl complexes clarified the details of the changes in the electronic states on the Ni centers; i.e., the electron delocalization was effectively enhanced among the Ni atom and CO ligands in the heterobimetallic Ni/Al species. The results presented in this work thus provide a strategy for reversibly modulating both the electronic and spatial environment of organometallic complexes, in addn. to the well-accepted Lewis-base-mediated ligand-substitution methods.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhsV2itb%252FJ&md5=8bc1e4a313876cb15439e92ddac5a413
  34. 34
    Carden, J. L.; Dasgupta, A.; Melen, R. L. Halogenated triarylboranes: synthesis, properties and applications in catalysis. Chem. Soc. Rev. 2020, 49, 1706– 1725,  DOI: 10.1039/C9CS00769E
    Google Scholar
    34
    Halogenated triarylboranes: synthesis, properties and applications in catalysis
    Carden, Jamie L.; Dasgupta, Ayan; Melen, Rebecca L.
    Chemical Society Reviews (2020), 49 (6), 1706-1725CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    A review discusses Lewis acidity detn. of boranes and the synthesis of these boranes and examples of how they are being used for catalysis and frustrated Lewis pair (FLP) chem. are explained. Halogenated triarylboranes (BAr3) were known for decades, however it has only been since the surge of interest in main group catalysis that their application as strong Lewis acid catalysts was recognized. This review aims to look past the popular tris(pentafluorophenyl)borane [B(C6F5)3] to the other halogenated triarylboranes, to give a greater breadth of understanding as to how tuning the Lewis acidity of BAr3 by modifications of the aryl rings can lead to improved reactivity.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXjvVKmtbg%253D&md5=1c835b98453c686738c42bd3f67f405f
  35. 35
    Ashley, A. E.; Herrington, T. J.; Wildgoose, G. G.; Zaher, H.; Thompson, A. L.; Rees, N. H.; Krämer, T.; O’hare, D. Separating Electrophilicity and Lewis Acidity: The Synthesis, Characterization, and Electrochemistry of the Electron Deficient Tris(aryl)boranes B(C6F5)3-n(C6Cl5)n (n = 1–3). J. Am. Chem. Soc. 2011, 133, 14727– 14740,  DOI: 10.1021/ja205037t
    Google Scholar
    35
    Separating electrophilicity and lewis acidity: the synthesis, characterization, and electrochemistry of the electron deficient tris(aryl)boranes B(C6F5)3-n(C6Cl5)n (n = 1-3)
    Ashley, Andrew E.; Herrington, Thomas J.; Wildgoose, Gregory G.; Zaher, Hasna; Thompson, Amber L.; Rees, Nicholas H.; Kramer, Tobias; O'Hare, Dermot
    Journal of the American Chemical Society (2011), 133 (37), 14727-14740CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    A new family of electron-deficient triarylboranes, B(C6F5)3-n(C6Cl5)n (n = 1-3), has been synthesized, permitting an investigation into the steric and electronic effects resulting from the gradual replacement of C6F5 with C6Cl5 ligands. B(C6F5)2(C6Cl5) (3) is accessed via C6Cl5BBr2, itself prepd. from donor-free Zn(C6Cl5)2 and BBr3. Reaction of C6Cl5Li with BCl3 in a Et2O/hexane slurry selectively produced B(C6Cl5)2Cl, which undergoes B-Cl exchange with CuC6F5 to afford B(C6F5)(C6Cl5)2 (5). While 3 forms a complex with H2O, which can be rapidly removed under vacuum or in the presence of mol. sieves, B(C6Cl5)3 (6) is completely stable to refluxing toluene/H2O for several days. Compds. 3, 5, and 6 have been structurally characterized using single crystal x-ray diffraction and represent the first structure detns. for compds. featuring B-C6Cl5 bonds; each exhibits a trigonal planar geometry about B, despite having different ligand sets. The spectroscopic characterization using 11B, 19F, and 13C NMR indicates that the boron center becomes more electron-deficient as n increases. Optimized structures of B(C6F5)3-n(C6Cl5)n (n = 0-3) using d. functional theory (B3LYP/TZVP) are all fully consistent with the exptl. structural data. Computed 11B shielding consts. also replicate the exptl. trend almost quant., and the computed natural charges on the boron center increase in the order n = 0 (0.81) < n = 1 (0.89) < n = 2 (1.02) < n = 3 (1.16), supporting the hypothesis that electrophilicity increases concomitantly with substitution of C6F5 for C6Cl5. The direct soln. cyclic voltammetry of B(C6F5)3 has been obtained for the first time and electrochem. measurements upon the entire series B(C6F5)3-n(C6Cl5)n (n = 0-3) corroborate the spectroscopic data, revealing C6Cl5 to be a more electron-withdrawing group than C6F5, with a ca. +200 mV shift obsd. in the redn. potential per C6F5 group replaced. Conversely, use of the Gutmann-Beckett and Childs' methods to det. Lewis acidity on B(C6F5)3, 3, and 5 showed this property to diminish with increasing C6Cl5 content, which is attributed to the steric effects of the bulky C6Cl5 substituents. This conflict is ascribed to the minimal structural reorganization in the radical anions upon redn. during cyclic voltammetric expts. Redn. of 6 using sodium soln. in THF results in a vivid blue paramagnetic soln. of Na+ [6]·-; the EPR signal of Na+[6]·- is centered at g = 2.002 with a(11B) 10G. Measurements of the exponential decay of the EPR signal (298 K) reveal [6]·- to be considerably more stable than its perfluoro analog.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtVOnsr7J&md5=3e265507590896cdeefef794ad9877aa
  36. 36
    Sakuraba, M.; Hoshimoto, Y. Recent Trends in Triarylborane Chemistry: Diversification of Structures and Reactivity via meta-Substitution of the Aryl Groups. Synthesis 2024, 56, 3421,  DOI: 10.1055/s-0043-1775394
    Google Scholar
    There is no corresponding record for this reference.
  37. 37
    Braunschweig, H.; Dewhurst, R. D.; Gessner, V. H. Transition metal borylene complexes. Chem. Soc. Rev. 2013, 42, 3197– 3208,  DOI: 10.1039/c3cs35510a
    Google Scholar
    37
    Transition metal borylene complexes
    Braunschweig, Holger; Dewhurst, Rian D.; Gessner, Viktoria H.
    Chemical Society Reviews (2013), 42 (8), 3197-3208CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    A review. Borylene ligands (:BR) are isolobal to CO and other iconic organometallic ligands. As such, borylene ligands enjoy some parallels to these ligands, but in many ways, their chem. is distinct. This tutorial review gives an introduction to the synthesis, properties and reactivity of the major classes of transition metal borylene complexes, including terminal and bridging examples, pseudoborylenes, and metalloborylenes (borido complexes).
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXksFemsLs%253D&md5=d93a2e913656a836f584b5d88b7c19d8
  38. 38
    Kong, L.; Lu, W.; Yongxin, Y.; Ganguly, R.; Kinjo, R. Formation of Boron–Main-Group Element Bonds by Reactions with a Tricoordinate Organoboron L2PhB: (L = Oxazol-2-ylidene). Inorg. Chem. 2017, 56, 5586– 5593,  DOI: 10.1021/acs.inorgchem.6b02993
    Google Scholar
    38
    Formation of Boron-Main-Group Element Bonds by Reactions with a Tricoordinate Organoboron L2PhB: (L = Oxazol-2-ylidene)
    Kong, Lingbing; Lu, Wei; Yongxin, Li; Ganguly, Rakesh; Kinjo, Rei
    Inorganic Chemistry (2017), 56 (10), 5586-5593CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    Reactivity of L2PhB: (1; L = 3,4,4-trimethyl-2-oxazolidinylidene) as well as its transition metal (Cr, Fe) complexes toward main group substrates have been systematically examd., which led construction of B-E (E = C, Ga, Cl, H, F, N) bonds. The combination of 1 and triethylborane (Et3B) smoothly captured carbon dioxide (CO2) concomitant with the formation of B-C and B-O bonds. The soft basic boron center in 1 readily reacted with soft acidic gallium trichloride (GaCl3) to afford extremely stable adduct [L2PhBGaCl3] (4) involving a B-Ga bond. Alkylation of neutral tricoordinate organoboron was first achieved by treatment of 1 with dichloromethane (DCM) and Me trifluoromethanesulfonate (MeOTf), both of which afforded ionic species [L2PhBCH2Cl]Cl (5) and [L2PhBMe][OTf] (6), featuring an addnl. B-C bond. Comparatively, redox reactions took place when halides of heavier elements such as germanium dichloride (GeCl2), dichlorophenylphosphine (PhPCl2) and chlorodiphenylbismuth (Ph2BiCl) were employed as substrates, from which cationic species [L2PhBCl]Cl (7) bearing a B-Cl bond was obtained. In addn., reactions of metal complexes [L2PhBM(CO)n] (2, M = Cr, n = 5; 8, M = Fe, n = 4) with cationic electrophiles were investigated. With HOTf and FN(SO2Ph)2, the corresponding ionic species featuring a B-H bond [L2PhBH][OTf] (9), a B-F bond [L2PhBF][N(SO2Ph)2] (10) were formed via a formal electrophilic substitution reaction whereas the reaction of 1 with F•Py-BF4 resulted in the formation of a dicationic boron species [L2PhB(py)][BF4]2 (11) with a B-N bond.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhs1Ois78%253D&md5=4e0ed60dd9d3462b675ecb6e86eee612
  39. 39
    Reineke, M. H.; Sampson, M. D.; Rheingold, A. L.; Kubiak, C. P. Synthesis and Structural Studies of Nickel(0) Tetracarbene Complexes with the Introduction of a New Four-Coordinate Geometric Index, τδ. Inorg. Chem. 2015, 54, 3211– 3217,  DOI: 10.1021/ic502792q
    Google Scholar
    39
    Synthesis and Structural Studies of Nickel(0) Tetracarbene Complexes with the Introduction of a New Four-Coordinate Geometric Index, τδ
    Reineke, Mark H.; Sampson, Matthew D.; Rheingold, Arnold L.; Kubiak, Clifford P.
    Inorganic Chemistry (2015), 54 (7), 3211-3217CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    The synthesis and characterization of two homoleptic chelating Ni(0) tetracarbene complexes are reported. These are the 1st Group 10 M(0) (M = Ni, Pd, Pt) tetracarbene complexes. These species have geometries intermediate between C2v sawhorse and tetrahedral and show high UV-visible absorption in the 350-600 nm range, with extinction coeffs. (ε) between 5600 and 9400 M-1 cm-1. D. functional theory anal. indicates that this high absorptivity is due to metal-to-ligand charge transfer. To better describe the unusual geometries encountered in these complexes, an adjustment to the popular τ4 index for four-coordinate geometries is introduced to better delineate between sawhorse and distorted tetrahedral geometries.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXkt1Ojsb0%253D&md5=7b81523cd3d0587c779d150ce88825cb
  40. 40
    Holschumacher, D.; Bannenberg, T.; Hrib, C. G.; Jones, P. G.; Tamm, M. Heterolytic Dihydrogen Activation by a Frustrated Carbene-Borane Lewis Pair. Angew. Chem., Int. Ed. 2008, 47, 7428– 7432,  DOI: 10.1002/anie.200802705
    Google Scholar
    40
    Heterolytic dihydrogen activation by a frustrated carbene-borane Lewis pair
    Holschumacher, Dirk; Bannenberg, Thomas; Hrib, Cristian G.; Jones, Peter G.; Tamm, Matthias
    Angewandte Chemie, International Edition (2008), 47 (39), 7428-7432CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The sterically demanding carbene 1,3-di-tert-butyl-1,3-dihydro-2H-imidazol-2-ylidene and B(C6F5)3, a frustrated Lewis pair, is a viable system for the activation of C-O, H-H, and C-H bonds. However, slow rearrangement to an abnormal carbene-borane adduct allows the irreversible formation of a strong B-C bond and enables this system to circumvent frustration at the expense of its activity. The crystal and mol. structures of imidazoliumyl- and (imidazoliumylbutoxy)boron zwitterions and imidazolium hydrotriarylborate were detd. by x-ray crystallog. Optimized structures and potential energy profiles were calcd. using B3LYP DFT.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXht1Shu7jN&md5=7aab94e9873941ad26d5c28cc1cbf4d7
  41. 41
    Chase, P. A.; Stephan, D. W. Hydrogen and Amine Activation by a Frustrated Lewis Pair of a Bulky N-Heterocyclic Carbene and B(C6F5)3. Angew. Chem., Int. Ed. 2008, 47, 7433– 7437,  DOI: 10.1002/anie.200802596
    Google Scholar
    41
    Hydrogen and amine activation by a frustrated Lewis pair of a bulky N-heterocyclic carbene and B(C6F5)3
    Chase, Preston A.; Stephan, Douglas W.
    Angewandte Chemie, International Edition (2008), 47 (39), 7433-7437CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The frustrated Lewis pair derived from B(C6F5)3 and the sterically encumbered N-heterocyclic carbene N,N'-tBu2C3H2N2 cleaves dihydrogen heterolytically to give a imidazolium borate, and cleaves amine N-H bonds to form aminoborate salts or aminoboranes.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXht1Shu7jO&md5=2387bf7931cb443e91156ada5c99ffa7
  42. 42
    Choukroun, R.; Lorber, C.; Lepetit, C.; Donnadieu, B. Reactivity of [Cp2Ti(CO)2] and B(C6F5)3: Formation of the Acylborane Complexes [Cp2Ti(CO)(η2-OCB(C6F5)3)] and [Cp2Ti(THF)(η2-OCB(C6F5)3)]. Organometallics 2003, 22, 1995– 1997,  DOI: 10.1021/om030185t
    Google Scholar
    42
    Reactivity of [Cp2Ti(CO)2] and B(C6F5)3: Formation of the Acylborane Complexes [Cp2Ti(CO)(η2-OCB(C6F5)3)] and [Cp2Ti(THF)(η2-OCB(C6F5)3)]
    Choukroun, Robert; Lorber, Christian; Lepetit, Christine; Donnadieu, Bruno
    Organometallics (2003), 22 (10), 1995-1997CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
    The reaction of [Cp2Ti(CO)2] with B(C6F5)3 leads, surprisingly, as revealed by x-ray structure detn. to the unexpected titana acylborane [Cp2Ti(L)(η2-OCB(C6F5)3)] (1, L = CO, "O-outside" configuration; 2, L = THF, "O-inside" configuration) with the tris(perfluorophenyl)borane, as a Lewis acid, attached to the carbonyl carbon atom. The acylborane picture is strengthened by a theor. calcn. (ELF).
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXis1Ohu7c%253D&md5=a044128936d91ce446ab60a860895069
  43. 43
    Lyngdoh, R. H. D.; Schaefer, H. F.; King, R. B. Metal-Metal (MM) Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc. Chem. Rev. 2018, 118, 11626– 11706,  DOI: 10.1021/acs.chemrev.8b00297
    Google Scholar
    There is no corresponding record for this reference.
  44. 44
    Shriver, D. F. BASCITY AND REACTIVITY OF METAL CARBONYLS. J. Organomet. Chem. 1975, 94, 259– 271,  DOI: 10.1016/S0022-328X(00)88721-5
    Google Scholar
    44
    Basicity and reactivity of metal carbonyls
    Shriver, D. F.
    Journal of Organometallic Chemistry (1975), 94 (2), 259-71CODEN: JORCAI; ISSN:0022-328X.
    A review with 45 refs.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE2MXkvFGkt7s%253D&md5=00d222e3f0312df326eb24a531194086
  45. 45
    Gong, J.-K.; Kubiak, C. P. A New Route to the Ni(0) ‘Cradle’ Complex Ni2(μ-CO)(CO)2(PPh2CH2PPh2)2: μ-CO Ligand and Metal-centered Reactivity. Inorg. Chim. Acta 1989, 162, 19– 21,  DOI: 10.1016/S0020-1693(00)83112-6
    Google Scholar
    45
    A new route to the nickel(0) 'cradle' complex bis[bis(diphenylphosphino)methane](μ-carbonyl)dicarbonyldinickel: μ-carbonyl ligand and metal-centered reactivity
    Gong, Jin Kang; Kubiak, Clifford P.
    Inorganica Chimica Acta (1989), 162 (1), 19-21CODEN: ICHAA3; ISSN:0020-1693.
    Ni2(μ-CO)(CO)2(Ph2PCH2PPh2)2 (I) was prepd. by the reaction of Ni(COD)3 (COD = cyclooctadiene) with (Ph2P)2CH2 and CO in toluene. I reacted with AlR3 (R = Me, Et) to give Ni2(μ-CO)(AlR3)(CO)2(Ph2PCH2PPh2)2 (II). I reacted with HPF6 to give [Ni2(μ-CO)(μ-H)(CO)2(Ph2PCH2PPh2)2]PF6. In II AlR3 is coordinated to the μ-CO ligand. The reaction of I with H+ leads to metal-centered reactivity. The complexes were characterized by IR and 1H NMR spectra.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3cXhslSrtLk%253D&md5=dc976da7896b4573d44f342d0170b7b6
  46. 46
    Bernhardt, E.; Finze, M.; Willner, H.; Lehmann, C. W.; Aubke, F. Salts of the Cobalt(I) Complexes [Co(CO)5]+ and [Co(CO)2(NO)2]+ and the Lewis Acid-Base Adduct [Co2(CO)7CO-B(CF3)3]. Chem.─Eur. J. 2006, 12, 8276– 8283,  DOI: 10.1002/chem.200600210
    Google Scholar
    46
    Salts of the cobalt(I) complexes [Co(CO)5]+ and [Co(CO)2(NO)2]+ and the Lewis acid-base adduct [Co2(CO)7CO-B(CF3)3]
    Bernhardt, Eduard; Finze, Maik; Willner, Helge; Lehmann, Christian W.; Aubke, Friedhelm
    Chemistry - A European Journal (2006), 12 (32), 8276-8283CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The reaction of [Co2(CO)8] with (CF3)3BCO in hexane leads to the Lewis acid-base adduct [Co2(CO)7CO-B(CF3)3] in high yield. When the reaction was performed in anhyd. HF soln. [Co(CO)5][(CF3)3BF] is isolated. The product contains the 1st example of a homoleptic metal pentacarbonyl cation with 18 valence electrons and a trigonal-bipyramidal structure. Treatment of [Co2(CO)8] or [Co(CO)3NO] with NO+ salts of weakly coordinating anions results in mixed crystals contg. the [Co(CO)5]+/[Co(CO)2(NO)2]+ ions or pure novel [Co(CO)2(NO)2]+ salts, resp. This is a promising route to other new metal carbonyl nitrosyl cations or even homoleptic metal nitrosyl cations. All compds. were characterized by vibrational spectroscopy and by single-crystal x-ray diffraction.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28Xht1ektbjI&md5=b297a89957a5727d18aa421462832e12
  47. 47
    Wade, C. R.; Lin, T.-P.; Nelson, R. C.; Mader, E. A.; Miller, J. T.; Gabbaï, F. P. Synthesis, Structure, and Properties of a T-shaped 14-Electron Stiboranyl-Gold Complex. J. Am. Chem. Soc. 2011, 133, 8948– 8955,  DOI: 10.1021/ja201092g
    Google Scholar
    47
    Synthesis, Structure, and Properties of a T-Shaped 14-Electron Stiboranyl-Gold Complex
    Wade, Casey R.; Lin, Tzu-Pin; Nelson, Ryan C.; Mader, Elizabeth A.; Miller, Jeffrey T.; Gabbai, Francois P.
    Journal of the American Chemical Society (2011), 133 (23), 8948-8955CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    A cyclic stiboranyl-gold complex I supported by two 1,8-naphthalenediyl linkers has been synthesized and structurally characterized. The gold atom of this complex adopts a T-shaped geometry and is sepd. from the antimony center by only 2.76 Å. Surprisingly, the trivalent gold atom of this complex is involved in an aurophilic interaction, a phenomenon typically only obsd. for monovalent gold complexes. This phenomenon indicates that the stiboranyl ligand possesses strong σ-donating properties making the trivalent gold atom of I electron rich. This view is supported by DFT calcns. as well as Au L3- and Sb K-edge XANES spectra which reveal that I may also be described as an aurate-stibonium deriv. In agreement with this view, complex I shows no reactivity toward the halides Cl-, Br-, and I-. It does, however, rapidly react with F- to form an unprecedented anionic aurate fluorostiborane complex ([2]-) which has been isolated as the tetra-n-butylammonium salt. The increased coordination no. of the antimony center in this anionic complex ([2]-) does not notably affect the Au-Sb sepn. (2.77 Å) or the geometry at the gold atom which remains T-shaped.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXmsFymu7c%253D&md5=5ae295588aac3232d8f3230a0f887858
  48. 48
    Ansmann, N.; Münch, J.; Schorpp, M.; Greb, L. Neutral and Anionic Square Planar Palladium(0) Complexes Stabilized by a Silicon Z-Type Ligand. Angew. Chem., Int. Ed. 2023, 62, e202313636  DOI: 10.1002/anie.202313636
    Google Scholar
    There is no corresponding record for this reference.
  49. 49
    For examples including Pt-complexes, see:Kameo, H.; Tanaka, Y.; Shimoyama, Y.; Izumi, D.; Matsuzaka, H.; Nakajima, Y.; Lavedan, P.; Le Gac, A.; Bourissou, D. Square-Planar Anionic Pt0 Complexes. Angew. Chem., Int. Ed. 2023, 62, e202301509  DOI: 10.1002/anie.202301509
    Google Scholar
    There is no corresponding record for this reference.
  50. 50
    Wächtler, E.; Gericke, R.; Block, T.; Pöttgen, R.; Wagler, J. Trivalent Antimony as L-, X-, and Z-Type Ligand: The Full Set of Possible Coordination Modes in Pt-Sb Bonds. Inorg. Chem. 2020, 59, 15541– 15552,  DOI: 10.1021/acs.inorgchem.0c02615
    Google Scholar
    There is no corresponding record for this reference.
  51. 51
    For examples including Au-complexes, see:Sircoglou, M.; Bontemps, S.; Mercy, M.; Saffon, N.; Takahashi, M.; Bouhadir, G.; Maron, L.; Bourissou, D. Transition-Metal Complexes Featuring Z-Type Ligands: Agreement or Discrepancy between Geometry and dn Configuration?. Angew. Chem., Int. Ed. 2007, 46, 8583– 8586,  DOI: 10.1002/anie.200703518
    Google Scholar
    51
    Transition-metal complexes featuring Z-type ligands: agreement or discrepancy between geometry and dn configuration?
    Sircoglou, Marie; Bontemps, Sebastien; Mercy, Maxime; Saffon, Nathalie; Takahashi, Masashi; Bouhadir, Ghenwa; Maron, Laurent; Bourissou, Didier
    Angewandte Chemie, International Edition (2007), 46 (45), 8583-8586CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A combined exptl. and theor. study of [AuCl(diphosphanylborane)] complexes featuring short Au-B contacts is reported. The coordination of ambiphilic diphosphanylborane ligands to AuCl provides unusual square-planar Au(I) complexes. Insight is gained on the Au → borane interactions in these complexes through natural bond orbital (NBO) anal. and 197Au Mossbauer spectroscopy.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtl2rsrnK&md5=58e9ebf97b2d45632db20151b9a2b797
  52. 52
    Dimucci, I. M.; Lukens, J. T.; Chatterjee, S.; Carsch, K. M.; Titus, C. J.; Lee, S. J.; Nordlund, D.; Betley, T. A.; MacMillan, S. N.; Lancaster, K. M. The Myth of d8 Copper(III). J. Am. Chem. Soc. 2019, 141, 18508– 18520,  DOI: 10.1021/jacs.9b09016
    Google Scholar
    52
    The Myth of d8 Copper(III)
    DiMucci, Ida M.; Lukens, James T.; Chatterjee, Sudipta; Carsch, Kurtis M.; Titus, Charles J.; Lee, Sang Jun; Nordlund, Dennis; Betley, Theodore A.; MacMillan, Samantha N.; Lancaster, Kyle M.
    Journal of the American Chemical Society (2019), 141 (46), 18508-18520CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Seventeen Cu complexes with formal oxidn. states ranging from CuI to CuIII are investigated through the use of multiedge X-ray absorption spectroscopy (XAS) and d. functional theory (DFT) calcns. Anal. reveals that the metal-ligand bonding in high-valent, formally CuIII species is extremely covalent, resulting in Cu K-edge and L2,3-edge spectra whose features have energies that complicate phys. oxidn. state assignment. Covalency anal. of the Cu L2,3-edge data reveals that all formally CuIII species have significantly diminished Cu d character in their lowest unoccupied MOs (LUMOs). DFT calcns. provide further validation of the orbital compn. anal., and excellent agreement is found between the calcd. and exptl. results. The finding that Cu has limited capacity to be oxidized necessitates localization of electron hole character on the supporting ligands; consequently, the phys. d8 description for these formally CuIII species is inaccurate. This study provides an alternative explanation for the competence of formally CuIII species in transformations that are traditionally described as metal-centered, 2-electron CuI/CuIII redox processes.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXitFWlu7rJ&md5=a7bb0efcded5f6960961592f4c0a2757
  53. 53
    DiMucci, I. M.; Titus, C. J.; Nordlund, D.; Bour, J. R.; Chong, E.; Grigas, D. P.; Hu, C. H.; Kosobokov, M. D.; Martin, C. D.; Mirica, L. M.; Nebra, N.; Vicic, D. A.; Yorks, L. L.; Yruegas, S.; MacMillan, S. N.; Shearer, J.; Lancaster, K. M. Scrutinizing Formally NiIV centers through the lenses of core spectroscopy, molecular orbital theory, and valence bond theory. Chem. Sci. 2023, 14, 6915– 6929,  DOI: 10.1039/D3SC02001K
    Google Scholar
    There is no corresponding record for this reference.
  54. 54
    Tran, V. T.; Li, Z. Q.; Apolinar, O.; Derosa, J.; Joannou, M. V.; Wisniewski, S. R.; Eastgate, M. D.; Engle, K. M. Ni(COD)(DQ): An Air-Stable 18-Electron Nickel(0)-Olefin Precatalyst. Angew. Chem., Int. Ed. 2020, 59, 7409– 7413,  DOI: 10.1002/anie.202000124
    Google Scholar
    54
    Ni(COD)(DQ): An Air-Stable 18-Electron Nickel(0)-Olefin Precatalyst
    Tran, Van T.; Li, Zi-Qi; Apolinar, Omar; Derosa, Joseph; Joannou, Matthew V.; Wisniewski, Steven R.; Eastgate, Martin D.; Engle, Keary M.
    Angewandte Chemie, International Edition (2020), 59 (19), 7409-7413CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    We report that Ni(COD)(DQ) (COD = 1,5-cyclooctadiene, DQ = duroquinone), an air-stable 18-electron complex originally described by Schrauzer in 1962, is a competent precatalyst for a variety of nickel-catalyzed synthetic methods from the literature. Due to its apparent stability, use of Ni(COD)(DQ) as a precatalyst allows reactions to be conveniently performed without use of an inert-atm. glovebox, as demonstrated across several case studies.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXltlelsbo%253D&md5=f9c3b2de5250c2e8109164422aea1ac6
  55. 55
    Hatsui, T.; Kosugi, N. Metal-to-ligand charge transfer in polarized metal L-edge X-ray absorption of Ni and Cu Complexes. J. Electron Spectrosc. Relat. Phenom. 2004, 136, 67– 75,  DOI: 10.1016/j.elspec.2004.02.133
    Google Scholar
    55
    Metal-to-ligand charge transfer in polarized metal L-edge X-ray absorption of Ni and Cu complexes
    Hatsui, Takaki; Kosugi, Nobuhiro
    Journal of Electron Spectroscopy and Related Phenomena (2004), 136 (1-2), 67-75CODEN: JESRAW; ISSN:0368-2048. (Elsevier Science B.V.)
    Metal L-edge x-ray absorption spectra for Ni and Cu complexes are discussed by studying their linear polarization dependence. The origin of the characteristic bands is revealed to be 1-electron transitions to ligand-centered MOs carrying metal-to-ligand charge transfer (MLCT). These MLCT transitions are related to the electronic structure of the ground state, particularly, the back-donation. Polarized L-edge x-ray absorption spectroscopy is applied to reveal electronic structures of metal complexes with doped hole and Ni-Ni bonding.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXjsl2mtrw%253D&md5=2893907fad1060294c749dd780dc3a0a
  56. 56
    Solomon, E. I.; Hedman, B.; Hodgson, K. O.; Dey, A.; Szilagyi, R. K. Ligand K-Edge X-ray aabsorption spectroscopy: covalency of ligand-metal bonds. Coord. Chem. Rev. 2005, 249, 97– 129,  DOI: 10.1016/j.ccr.2004.03.020
    Google Scholar
    56
    Ligand K-edge X-ray absorption spectroscopy: covalency of ligand-metal bonds
    Solomon, Edward I.; Hedman, Britt; Hodgson, Keith O.; Dey, Abhishek; Szilagyi, Robert K.
    Coordination Chemistry Reviews (2005), 249 (1-2), 97-129CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
    A review. The ligand K-edge probes the ligand 1s → valence np transitions. These transitions acquire intensity when the ligand is bound to an open shell metal ion. This intensity quantifies the amt. of ligand character in the metal d orbitals, hence the covalency of the ligand-metal bond. In this review the methodol. is developed and applied to Cu proteins, Fe-S sites and Ni dithiolene complexes, as examples. These illustrate the power and impact of this method in evaluating covalency contributions to electron transfer pathways, redn. potentials, H-bond interactions, electron delocalization in mixed-valent systems and small mol. reactivity.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXhtFejs7zI&md5=e308ff93e025768f574c66267d1a680a
  57. 57
    Sarangi, R.; George, S. D. B.; Rudd, D. J.; Szilagyi, R. K.; Ribas, X.; Rovira, C.; Almeida, M.; Hodgson, K. O.; Hedman, B.; Solomon, E. I. Sulfur K-Edge X-ray Absorption Spectroscopy as a Probe of Ligand-Metal Bond Covalency: Metal vs Ligand Oxidation in Copper and Nickel Dithiolene Complexes. J. Am. Chem. Soc. 2007, 129, 2316– 2326,  DOI: 10.1021/ja0665949
    Google Scholar
    57
    Sulfur K-Edge X-ray Absorption Spectroscopy as a Probe of Ligand-Metal Bond Covalency: Metal vs Ligand Oxidation in Copper and Nickel Dithiolene Complexes
    Sarangi, Ritimukta; DeBeer George, Serena; Rudd, Deanne Jackson; Szilagyi, Robert K.; Ribas, Xavi; Rovira, Concepcio; Almeida, Manuel; Hodgson, Keith O.; Hedman, Britt; Solomon, Edward I.
    Journal of the American Chemical Society (2007), 129 (8), 2316-2326CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    A combination of Cu L-edge and S K-edge X-ray absorption data and d. functional theory (DFT) calcns. has been correlated with 33S ESR superhyperfine results to obtain the dipole integral (Is) for the S 1s→3p transition for the dithiolene ligand maleonitriledithiolate (MNT) in (TBA)2[Cu(MNT)2] (TBA= tetra-n-butylammonium). The results have been combined with the Is of sulfide derived from XPS studies to exptl. obtain a relation between the S 1s→4p transition energy (which reflects the charge on the S atom, QmolS) and the dipole integral over a large range of QmolS. The results show that, for high charges on S, Is can vary from the previously reported Is values, calcd. using data over a limited range of QmolS. A combination of S K-edge and Cu K- and L-edge X-ray absorption data and DFT calcns. has been used to investigate the one-electron oxidn. of [Cu(MNT)2]2- and [Ni(MNT)2]2-. The conversion of [Cu(MNT)2]2- to [Cu(MNT)2]- results in a large change in the charge on the Cu atom in the mol. (QmolCu) and is consistent with a metal-based oxidn. This is accompanied by extensive charge donation from the ligands to compensate the high charge on the Cu in [Cu(MNT)2]- based on the increased S K-edge and decreased Cu L-edge intensity, resp. In contrast, the oxidn. of [Ni(MNT)2]2- to [Ni(MNT)2]- results in a small change in QmolNi, indicating a ligand-based oxidn. consistent with oxidn. of a MO, ψ*SOMO (singly occupied MO), with predominant ligand character.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtlemtb0%253D&md5=77cd3a8074a6cf06f1ee0728ac766b3f

Cited By

Click to copy section linkSection link copied!

This article has not yet been cited by other publications.

Download PDF
Go to Journal of the American Chemical Society
Get e-Alerts
Get e-Alerts

Journal of the American Chemical Society

Cite this: J. Am. Chem. Soc. 2025, 147, 10, 8326–8335
Click to copy citationCitation copied!
https://doi.org/10.1021/jacs.4c15892
Published February 28, 2025

Copyright © 2025 The Authors. Published by American Chemical Society. This publication is licensed under

CC-BY-NC-ND 4.0 .

Article Views

4816

Altmetric

-

Citations

-
Learn about these metrics

Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.

Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.

The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated.

  • Abstract

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 1

    Figure 1. Concept of electron acceptors and donors. (a) A simplified representation of complexation between Lewis acids (LAs) and Lewis bases (LBs) and the related orbitals. (b) Coordination of transition metals (TM) to trivalent group-13 species. (c) Pioneering examples of Ni complexes that bear LnZ-type borane ligands. (d) A strategy for monodentate Z-type borane ligands based on frustrated L/Z-ligand pairs (this work).

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 2

    Figure 2. Reaction between Ni-carbonyl complexes and triarylboranes. The isolated yield is shown with the NMR yield in parentheses; N.R.: no reaction; Dipp: 2,6-diisopropylphenyl; Mes: mesityl.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 3

    Figure 3. Molecular structures and electron densities for (a) 2a and (b) 6a. Each structure was obtained from the corresponding SC-XRD analysis. The quantum theory of AIM bond paths (white lines) and bond critical points (BCPs, green dots) are also shown with overlaid contour plots of ∇2ρ (e × rBohr–5) through the plane defined by the C2, Ni, and B atoms (∇2ρ < 0 shown in blue; ∇2ρ > 0 shown in red). The AIM methods used the SCF electron density calculated at the PBE0-D3BJ/Def2-TZVPD//M06L/Def2-SVPD(Ni,O,F), Def2-SVP(others) level. Electron densities (ρ in e × rBohr–3) at selected BCPs are given. Values of ∇2ρ are also given in parentheses. Selected bond lengths (Å) for 2a: Ni–C1 1.976(1), Ni–C2 1.697(1), Ni–B 2.245(1), Ni–O1 1.9916(9), C2–O2 1.154(1), Ni···F 2.7450(9); 6a: Ni–C1 1.946(2), Ni–C2 1.735(3), Ni–B 2.267(4), Ni–C3 2.110(2), Ni···C4 2.238(2), Ni–O1 2.320(2), C2–B 2.373(4), C2–O2 1.146(3).

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 4

    Figure 4. Effect of ligands. (a) Reaction with 1d–1f. (b) Reaction with 1g. The conversion of 1g through the transformation of 7g is shown in square brackets. The gas-phase optimized structure of 2g and the SC-XRD structure of 7g (except hydrogen atoms; thermal ellipsoids at 30% probability) are also shown. Selected bond lengths (Å) for 2g: Ni–C1 2.00, Ni–C2 1.82, Ni–B 2.43, C2–O 1.15; 7g: Ni–C1 1.976(4), Ni–O 1.966(3), Ni–C2 1.843(4), C2–O 1.207(5), C2–B 1.639(5).

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 5

    Figure 5. Plausible mechanisms for the formation of 2a. Relative Gibbs free energies (kcal mol–1) with respect to [1a + B1] (0.0 kcal mol–1) are shown, calculated at the PBE0-D3BJ/Def2-TZVPD//M06L/Def2-SVPD(Ni,F,O), Def2-SVP(others) level. Parts of the molecular structures for the selected compounds are also shown with selected bond lengths (Å).

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 6

    Figure 6. Experimental and theoretical evaluation of the electronic state of the Ni complexes examined in this study. (a) Ni K-edge XAS spectra. (b) Ni L2,3-edge XAS spectra. (c) Sum-rule analysis. (d) A simplified Frontier-molecular-orbital energy diagram of 2a, focusing on the interaction between the Ni and B centers, calculated at PBE0-D3BJ/Def2-TZVPD level. (e) Kohn–Sham HOMO and LUMO+1 in 2a and their orbital composition.

    High Resolution Image
    Download MS PowerPoint Slide

  • References

    This article references 57 other publications.

    1. 1
      Jensen, W. B. The Lewis Acid-Base Definitions: A Status Report. Chem. Rev. 1978, 78, 1– 31,  DOI: 10.1021/cr60311a002
      1
      The Lewis acid-base definitions: a status report
      Jensen, William B.
      Chemical Reviews (Washington, DC, United States) (1978), 78 (1), 1-22CODEN: CHREAY; ISSN:0009-2665.
      A review dealing with the historical, theor., and interpretive aspects of the Lewis definitions. 156 Refs.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE1cXnvFykug%253D%253D&md5=bc7c4a756a3337a2d068496e457d4a95
    2. 2
      Crawley, M. L.; Trost, B. M. Applications of Transition Metal Catalysis in Drug Discovery and Development: An Industrial Perspective; John Wiley & Sons, 2012; . DOI: 10.1002/9781118309872 .
      There is no corresponding record for this reference.
    3. 3
      Striegler, S.; Rieger, B.; Kacker, S.; Baugh, L. S. Late Transition Metal Polymerization Catalysis; Wiley VCH, 2003.
      There is no corresponding record for this reference.
    4. 4
      Hartwig, J. F. Organotransition Metal Chemistry: From Bonding to Catalysis; University Science Books, 2010.
      There is no corresponding record for this reference.
    5. 5
      Braunschweig, H.; Dewhurst, R. D.; Schneider, A. Electron-Precise Coordination Modes of Boron-Centered Ligands. Chem. Rev. 2010, 110, 3924– 3957,  DOI: 10.1021/cr900333n
      5
      Electron-Precise Coordination Modes of Boron-Centered Ligands
      Braunschweig, Holger; Dewhurst, Rian D.; Schneider, Achim
      Chemical Reviews (Washington, DC, United States) (2010), 110 (7), 3924-3957CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review summarizes the chem. of mol. compds. featuring "electron precise" two center covalent and dative transition metal-boron interactions such as with the BR3 fragment (borane complexes), BR2 ligands (boryl complexes), B-R fragments as terminal or bridging ligands (borylene complexes) or lone boron atom as ligand (boride complexes).
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXjtlaitLw%253D&md5=ba4c8b6a5a537c5fb63c502461bdb090
    6. 6
      Amgoune, A.; Bourissou, D. σ-Acceptor, Z-type ligands for transition Metals. Chem. Commun. 2011, 47, 859– 871,  DOI: 10.1039/C0CC04109B
      6
      σ-Acceptor, Z-type ligands for transition metals
      Amgoune, Abderrahmane; Bourissou, Didier
      Chemical Communications (Cambridge, United Kingdom) (2011), 47 (3), 859-871CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      A review. The ability of Lewis acids to coordinate to transition metals as σ-acceptor ligands was recognized as early as in the 1970's, but so-called Z-type ligands remained curiosities until the early 2000's. Over the last decade, significant progress was made in this area, esp. via the incorporation of Lewis acid moieties into multidentate, ambiphilic ligands. The authors' understanding of the nature and influence of TM → Z interactions has considerably improved and the scope of Lewis acids susceptible to behave as σ-acceptor ligands was significantly extended. This feature article summarizes these recent achievements.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhsF2isrbN&md5=d886ffe6c81105043b4cba0784c0c2c0
    7. 7
      Braunschweig, H.; Dewhurst, R. D. Transition metals as Lewis bases: “Z-type” boron ligands and metal-to-boron dative bonding. Dalton Trans. 2011, 40, 549– 558,  DOI: 10.1039/C0DT01181A
      7
      Transition metals as Lewis bases: "Z-type" boron ligands and metal-to-boron dative bonding
      Braunschweig, Holger; Dewhurst, Rian D.
      Dalton Transactions (2011), 40 (3), 549-558CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
      A review. While the vast majority of inorg. chem. involves electron donation from main-group atoms to metals, an intriguing yet flip-side exists: where Lewis-basic metals donate electron d. to Lewis-acidic main-group atoms (most often boron). These so-called Z-type ligands, along with other less clear-cut complexes, are examples of this metal-ligand role reversal. This perspective article offers an introduction to metal-to-boron dative bonding, and attempts to correlate spectroscopic and structural data from the complexes.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhs1WjtbrI&md5=c394f11b5e719dbfe05e715cf4998f4f
    8. 8
      Bauer, J.; Braunschweig, H.; Dewhurst, R. D. Metal-Only Lewis Pairs with Transition Metal Lewis Bases. Chem. Rev. 2012, 112, 4329– 4346,  DOI: 10.1021/cr3000048
      8
      Metal-Only Lewis Pairs with Transition Metal Lewis Bases
      Bauer, Juergen; Braunschweig, Holger; Dewhurst, Rian D.
      Chemical Reviews (Washington, DC, United States) (2012), 112 (8), 4329-4346CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. The following topics are discussed:the history of metal-metal dative bond concept; complexes with d-block metal → s/p-Block metal dative bonding; complexes with d-block metal → d/f-Block metal dative bonding; bridged and other boredline cases: complexes with Groups 6, 7, 8, 9, and 10 metal bases.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XnsVeqsrk%253D&md5=92c3322a8d827d824f27c5fee76a66c3
    9. 9
      Parkin, G. Impact of the coordination of multiple Lewis acid functions on the electronic structure and vn configuration of a metal center. Dalton Trans. 2022, 51, 411– 427,  DOI: 10.1039/D1DT02921E
      9
      Impact of the coordination of multiple Lewis acid functions on the electronic structure and vn configuration of a metal center
      Parkin, Gerard
      Dalton Transactions (2022), 51 (2), 411-427CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
      The covalent bond classification (CBC) method represents a mol. as MLlXxZz by evaluating the total no. of L, X and Z functions interacting with M. The CBC method is a simplistic approach that is based on the notion that the bonding of a ligating atom (or group of atoms) can be expressed in terms of the no. of electrons it contributes to a 2-electron bond. In many cases, the bonding in a mol. of interest can be described in terms of a 2-center 2-electron bonding model and the MLlXxZz classification can be derived straightforwardly by considering each ligand independently. However, the bonding within a mol. cannot always be described satisfactorily by using a 2-center 2-electron model and, in such situations, the MLlXxZz classification requires a more detailed consideration than one in which each ligand is treated in an independent manner. The purpose of this article is to provide examples of how the MLlXxZz classification is obtained in the presence of multicenter bonding interactions. Specific emphasis is given to the treatment of multiple π-acceptor ligands and the impact on the vn configuration, i.e. the no. of formally nonbonding electrons on an element of interest.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXislynsL%252FI&md5=7370cc77c8ae2576eb270e0b49d0e066
    10. 10
      Komuro, T.; Nakajima, Y.; Takaya, J.; Hashimoto, H. Recent progress in transition metal complexes supported by multidentate ligands featuring group 13 and 14 elements as coordinating atoms. Coord. Chem. Rev. 2022, 473, 214837– 214864,  DOI: 10.1016/j.ccr.2022.214837
      10
      Recent progress in transition metal complexes supported by multidentate ligands featuring group 13 and 14 elements as coordinating atoms
      Komuro, Takashi; Nakajima, Yumiko; Takaya, Jun; Hashimoto, Hisako
      Coordination Chemistry Reviews (2022), 473 (), 214837CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
      Over the past decade, significant progress has been made in the chem. of transition metal complexes supported by multidentate chelate ligands, such as pincer-type ligands, in line with the development of active transition metal catalysts. This review summarizes recent progress in this area, with a focus on the incorporation of electropos. Group 13 (B, Al, Ga, and In) and Group 14 (Si and Ge) elements into the supporting multidentate ligands as coordinating atoms. These electropos. element-based ligands afford complexes with unique functionalities, such as remarkably strong σ-donor ability, high trans influence, and σ-acceptor ability, depending on the types of supporting ligands: L-type (2e donor), X-type (1e donor), and Z-type (2e acceptor) ligands. This review mainly covers the synthesis, fundamental properties, and catalysis of the complexes bearing these ligands.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XisFCjsLvO&md5=b40dc0b528963c1cdb61ea7e775e9cd8
    11. 11
      Green, M. L. H. A new approach to the formal classification of covalent compounds of the elements. J. Organomet. Chem. 1995, 500, 127– 148,  DOI: 10.1016/0022-328X(95)00508-N
      11
      A new approach to the formal classification of covalent compounds of the elements
      Green, M. L. H.
      Journal of Organometallic Chemistry (1995), 500 (1-2), 127-48CODEN: JORCAI; ISSN:0022-328X. (Elsevier)
      A new approach to the classification of covalent compds. of the transition metals is presented. The classification introduces the concepts of valency no. and ligand bond no. as alternatives to the concepts of formal oxidn. state and coordination no. Population d. maps (MLX plots) which represent the covalent compds. of an element as a function of all the known ligands are exemplified for chromium; molybdenum and tungsten; and nickel, palladium and platinum. These plots are used to identify the major characteristic chem. properties of the elements including reactivity trends and reaction mechanisms.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXotlektr8%253D&md5=c0a64ae93f1ebb8fb9c77e03007833df
    12. 12
      Davydova, E. I.; Sevastianova, T. N.; Timoshkin, A. Y. Molecular complexes of group 13 element trihalides, pentafluorophenyl derivatives and Lewis superacids. Coord. Chem. Rev. 2015, 297, 91– 126,  DOI: 10.1016/j.ccr.2015.02.019
      There is no corresponding record for this reference.
    13. 13
      Cowley, A. H. From group 13–group 13 donor–acceptor bonds to triple-decker cations. Chem. Commun. 2004, 2369– 2375,  DOI: 10.1039/B409497M
      There is no corresponding record for this reference.
    14. 14
      Burlitch, J. M.; Leonowicz, M. E.; Petersen, R. B.; Hughes, R. E. Coordination of Metal Carbonyl Anions to Triphenylaluminum, -gallium, and -indium and the Crystal Structure of Tetraethylammonium Triphenyl((η5-Cyclopentadienyl)dicarbonyliron)aluminate(Fe–Al). Inorg. Chem. 1979, 18, 1097– 1105,  DOI: 10.1021/ic50194a040
      There is no corresponding record for this reference.
    15. 15
      Kameo, H.; Nakazawa, H. Saturated Heavier Group 14 Compounds as σ-Electron-Acceptor (Z-type) Ligands. Chem. Rec. 2017, 17, 268– 286,  DOI: 10.1002/tcr.201600061
      15
      Saturated Heavier Group 14 Compounds as σ-Electron-Acceptor (Z-Type) Ligands
      Kameo, Hajime; Nakazawa, Hiroshi
      Chemical Record (2017), 17 (3), 268-286CODEN: CRHEAK; ISSN:1528-0691. (Wiley-VCH Verlag GmbH & Co. KGaA)
      This review article describes the chem. of transition-metal complexes contg. heavier group 14 elements (Si, Ge, and Sn) as the σ-electron-acceptor (Z-type) ligands and discusses the characteristics of bonds between the transition metal and Z-type ligand. Moreover, we review the iridium hydride mediated cleavage of E-X bonds (E = Si, Ge; X = F, Cl), where the key intermediates are pentacoordinate silicon or germanium compds. bearing a dative M→E bond.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xht12ns7jF&md5=48c6e933a5b2d619e464e78950e7582c
    16. 16
      For examples including Pt-complexes, see:Bauer, J.; Braunschweig, H.; Dewhurst, R. D.; Radacki, K. Reactivity of Lewis Basic Platinum Complexes Towards Fluoroboranes. Chem.─Eur. J. 2013, 19, 8797– 8805,  DOI: 10.1002/chem.201301056
      16
      Reactivity of Lewis Basic Platinum Complexes Towards Fluoroboranes
      Bauer, Juergen; Braunschweig, Holger; Dewhurst, Rian D.; Radacki, Krzysztof
      Chemistry - A European Journal (2013), 19 (27), 8797-8805CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The interaction of Lewis acidic fluoroboranes, for example BF2Pf (Pf = perfluorophenyl) and BF2ArF (ArF = 3,5-bis(trifluoromethyl)phenyl), with Lewis basic Pt complexes such as [Pt(PEt3)3] and [Pt(PCy3)2] (Cy = cyclohexyl) is reported. Two presumed Lewis adducts could be identified in soln. and corresponding secondary products of these Lewis adducts were characterized in the solid state. Also, the concept of frustrated Lewis pairs (FLP) was applied to the activation of ethene in the system [Pt(BPf3)(CH2CH2)(dcpp)] (dcpp = 1,3-bis(dicyclohexylphosphino)propane; Pf = perfluorophenyl). Finally, DFT calcns. were performed to det. the interaction between the Pt-centered Lewis bases and the B-centered Lewis acids. Addnl., several possible mechanisms for the oxidative addn. of the boranes BF3, BCl3, and BF2ArF to the model complex [Pt(PMe3)2] are presented.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXnvVKqtLw%253D&md5=f78b83c2868637ada6f5dc794f96afe8
    17. 17
      For examples including Fe-complexes, see:Burlitch, J. M.; Burk, J. H.; Leonowicz, M. E.; Hughes, R. E. Migration of triphenylboron from iron to a geminal η5-cylopentadienyl ligand. Inorg. Chem. 1979, 18, 1702– 1709,  DOI: 10.1021/ic50196a061
      There is no corresponding record for this reference.
    18. 18
      For examples including Rh-complexes, see:Alférez, M. G.; Moreno, J. J.; Gaona, M. A.; Maya, C.; Campos, J. Ligand Postsynthetic Functionalization with Fluorinated Boranes and Implications in Hydrogenation Catalysis. ACS Catal. 2023, 13, 16055– 16066,  DOI: 10.1021/acscatal.3c02764
      There is no corresponding record for this reference.
    19. 19
      Hashimoto, T.; Asada, T.; Ogoshi, S.; Hoshimoto, Y. Main group catalysis for H2 purification based on liquid organic hydrogen carriers. Sci. Adv. 2022, 8, eade0189  DOI: 10.1126/sciadv.ade0189
      There is no corresponding record for this reference.
    20. 20
      Sakuraba, M.; Morishita, T.; Hashimoto, T.; Ogoshi, S.; Hoshimoto, Y. Remote Back Strain: A Strategy for Modulating the Reactivity of Triarylboranes. Synlett 2023, 34, 2187– 2192,  DOI: 10.1055/a-2110-5359
      There is no corresponding record for this reference.
    21. 21
      Hisata, Y.; Washio, T.; Takizawa, S.; Ogoshi, S.; Hoshimoto, Y. In-silico-assisted derivatization of triarylboranes for the ccatalytic reductive functionalization of aniline-derived amino acids and peptides with H2. Nat. Commun. 2024, 15, 3708,  DOI: 10.1038/s41467-024-47984-0
      There is no corresponding record for this reference.
    22. 22
      Goedecke, C.; Hillebrecht, P.; Uhlemann, T.; Haunschild, R.; Frenking, G. The Dewar-Chatt-Duncanson model reversed: Bonding analysis of group-10 complexes [(PMe3)2M–EX3] (M = Ni, Pd, Pt; E = B, Al, Ga, In, Tl; X = H, F, Cl, Br, I). Can. J. Chem. 2009, 87, 1470– 1479,  DOI: 10.1139/V09-099
      There is no corresponding record for this reference.
    23. 23
      Erdmann, P.; Greb, L. What Distinguishes the Strength and the Effect of a Lewis Acid: Analysis of the Gutmann–Beckett Method. Angew. Chem., Int. Ed. 2022, 61, e202114550  DOI: 10.1002/anie.202114550
      23
      What Distinguishes the Strength and the Effect of a Lewis Acid: Analysis of the Gutmann-Beckett Method
      Erdmann, Philipp; Greb, Lutz
      Angewandte Chemie, International Edition (2022), 61 (4), e202114550CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      IUPAC defines Lewis acidity as the thermodn. tendency for Lewis pair formation. This strength property was recently specified as global Lewis acidity (gLA), and is gauged for example by the fluoride ion affinity. Exptl., Lewis acidity is usually evaluated by the effect on a bound mol., such as the induced 31P NMR shift of triethylphosphine oxide in the Gutmann-Beckett (GB) method. This type of scaling was called effective Lewis acidity (eLA). Unfortunately, gLA and eLA often correlate poorly, but a reason for this is unknown. Hence, the strength and the effect of a Lewis acid are two distinct properties, but they are often granted interchangeably. The present work analyzes thermodn., NMR specific, and London dispersion effects on GB nos. for 130 Lewis acids by theory and expt. The deformation energy of a Lewis acid is identified as the prime cause for the crit. deviation between gLA and eLA but its correction allows a unification for the first time.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXislOhurnK&md5=c5de4510156ba53802263200b0f57618
    24. 24
      For examples including Ru-complexes, see:Hill, A. F.; Owen, G. R.; White, A. J. P.; Williams, D. J. The Sting of the Scorpion: A Metallaboratrane. Angew. Chem., Int. Ed. 1999, 38, 2759– 2761,  DOI: 10.1002/(SICI)1521-3773(19990917)38:18<2759::AID-ANIE2759>3.0.CO;2-P
      24
      The sting of the scorpion: a metallaboratrane
      Hill, Anthony F.; Owen, Gareth R.; White, Andrew J. P.; Williams, David J.
      Angewandte Chemie, International Edition (1999), 38 (18), 2759-2761CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH)
      The novel ruthenaboratrane complex [Ru{B(mt)3}(CO)(PPh3)] (4, mt = 2-sulfanyl-1-methylimidazolyl) was prepd. from the reaction of [Ru(CH:CHCPh2OH)Cl(CO)(PPh3)2] with Na[HB(mt)3] and characterized spectroscopically and by x-ray crystallog. (4·2CHCl3: triclinic, space group P‾1, R1 = 0.049). The complex has a Ru→B bond of 2.161(5) Å, resulting in a tetrahedral geometry for boron, and ruthenium is octahedral. This complex is the first example of a poly(azolyl)borate ligand that undergoes B-H activation (stinging of the "scorpionate") to give this metallaboratrane structure.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXmtl2rsLs%253D&md5=be4d43e88a21b9fcdf2c57be74b390b2
    25. 25
      Hill, A. F. An Unambiguous Electron-Counting Notation for Metallaboratranes. Organometallics 2006, 25, 4741– 4743,  DOI: 10.1021/om0602512
      25
      An Unambiguous Electron-Counting Notation for Metallaboratranes
      Hill, Anthony F.
      Organometallics (2006), 25 (20), 4741-4743CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
      As the field of metalloboratranes develops, a spectrum of behavior for the M→B bond will emerge, involving different degrees of electron transfer from metal to the Lewis acid. A cohesive notation for indicating the overall no. of electrons assocd. with the metal and the M-B unit should therefore serve to preempt confusion that might arise from electron-counting formalisms based on the contradictory dictums. It is hoped that adoption of the recommended (M→B)n notation wherein the superscript no. (n) denotes the total no. of electrons assocd. with the metal d orbitals and M→B group, will help obviate such a situation. E.g., complex [Os(CO)(PPh3){B(mt)3}] should be denoted (Os→B)8.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XotlCmsbk%253D&md5=2b10fc4086ab34921044606402de3ff3
    26. 26
      For examples including Rh-complexes, see:Crossley, I. R.; Hill, A. F.; Willis, A. C. Metallaboratranes: Tris(methimazolyl)borane Complexes of Rhodium(I). Organometallics 2006, 25, 289– 299,  DOI: 10.1021/om050772+
      26
      Metallaboratranes: Tris(methimazolyl)borane Complexes of Rhodium(I)
      Crossley, Ian R.; Hill, Anthony F.; Willis, Anthony C.
      Organometallics (2006), 25 (1), 289-299CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
      The syntheses and reactivity of the first rhodaboratranes, [RhX(PPh3){B(mt)3}] (X = Cl, H) and [Rh(η4-C8H12){B(mt)3}]Cl, are described in detail together with preliminary investigations of the mechanistic processes involved. The subsequent exploitation and circumvention of the lability of [RhCl(PPh3){B(mt)3}] in the synthesis of a range of isonitrile, [Rh(CNR)(PPh3){B(mt)3}]Cl (R = tBu, C6H3Me2-2,6, C6H2Me3-2,4,6), phosphine, [Rh(PMe3)n(PPh3)2-n{B(mt)3}]Cl (n = 0, 1, 2), and dialkyldithiocarbamate, [Rh(S2NEt2){B(mt)3}]Cl, complexes is described, along with the attempted synthesis of [Rh(CNtBu)2{B(mt)3}]Cl from [Rh(η4-C8H12){B(mt)3}]Cl. Single-crystal x-ray structure detns. of [Rh(L)(L'){B(mt)3}]Cl (L = CNtBu, CN(C6H3Me2-2,6), L' = PPh3; L = L' = PMe3) are reported.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXht1GmsLrL&md5=c308e273d26e859eb203f8aa51ae53ba
    27. 27
      Parkin, G. A. Simple Description of the Bonding in Transition-Metal Borane Complexes. Organometallics 2006, 25, 4744– 4747,  DOI: 10.1021/om060580u
      27
      A Simple Description of the Bonding in Transition-Metal Borane Complexes
      Parkin, Gerard
      Organometallics (2006), 25 (20), 4744-4747CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
      A review of nomenclature of the description of the bonding in transition-metal borane complexes.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XotlCmtr8%253D&md5=4d380ad53937c1634aef2c8878dbabf0
    28. 28
      For examples including Ni-, Cu-, Pd-, Ag-, Pt- and Au-complexes, see:Sircoglou, M.; Bontemps, S.; Bouhadir, G.; Saffon, N.; Miqueu, K.; Gu, W.; Mercy, M.; Chen, C.-H.; Foxman, B. M.; Maron, L.; Ozerov, O. V.; Bourissou, D. Group 10 and 11 Metal Boratranes (Ni, Pd, Pt, CuCl, AgCl, AuCl, and Au+) Derived from a Triphosphine–Borane. J. Am. Chem. Soc. 2008, 130, 16729– 16738,  DOI: 10.1021/ja8070072
      28
      Group 10 and 11 Metal Boratranes (Ni, Pd, Pt, CuCl, AgCl, AuCl, and Au+) Derived from a Triphosphine-Borane
      Sircoglou, Marie; Bontemps, Sebastien; Bouhadir, Ghenwa; Saffon, Nathalie; Miqueu, Karinne; Gu, Weixing; Mercy, Maxime; Chen, Chun-Hsing; Foxman, Bruce M.; Maron, Laurent; Ozerov, Oleg V.; Bourissou, Didier
      Journal of the American Chemical Society (2008), 130 (49), 16729-16738CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The ambiphilic triphosphine-borane ligand TPB (1, [o-iPr2P-C6H4]3B) readily coordinates to all Group 10 and 11 metals to afford a complete series of metal boratranes (TPB)[M] 2-8 (2: M = Ni, 3: M = Pd, 4: M = Pt, 5: M = CuCl, 6: M = AgCl, 7: M = AuCl, 8: M = Au+). Spectroscopic and structural characterization unambiguously establishes M→B interactions in all of these complexes. The 1st evidence for borane coordination to copper and silver is provided, and the Au→B interaction persists upon chloride abstraction. Exptl. and theor. considerations indicate that the M→B interaction is strongest in the Pt and Au complexes. The influence of the oxidn. state and charge of the metal is substantiated, and the consequences of relativistic effects are discussed. The coordination of the σ-acceptor borane ligand is found to induce a significant bathochromic shift of the UV-visible spectra, the Ni, Pd, and Pt complex presenting strong absorptions in the visible range. All of the group 10 and 11 metal boratranes adopt C3 symmetry both in the solid state and in soln. The central M→B interaction moderately influences the degree of helicity and configurational stability of these three-bladed propellers, and DFT calcns. support a dissociative pathway for the inversion process.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtlOlt7rN&md5=6309b00f4e0dd3ff44c1c9cc526c92f3
    29. 29
      For examples including Ni- and Pd-complexes, see:Emslie, D. J. H.; Harrington, L. E.; Jenkins, H. A.; Robertson, C. M.; Britten, J. F. Group 10 Transition-Metal Complexes of an Ambiphilic PSB-Ligand: Investigations into η3(BCC)-Triarylborane Coordination. Organometallics 2008, 27, 5317– 5325,  DOI: 10.1021/om800670e
      29
      Group 10 Transition-Metal Complexes of an Ambiphilic PSB-Ligand: Investigations into η3(BCC)-Triarylborane Coordination
      Emslie, David J. H.; Harrington, Laura E.; Jenkins, Hilary A.; Robertson, Craig M.; Britten, James F.
      Organometallics (2008), 27 (20), 5317-5325CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
      Reaction of 2,7-di-tert-butyl-5-diphenylboryl-4-diphenylphosphino-9,9-dimethylthioxanthene (TXPB) with [PdCl2(COD)] (COD = 1,5-cyclooctadiene) gave [PdCl(μ-Cl)(TXPB)] (3, 87% yield), which can be reduced in a stepwise fashion, forming [Pd(TXPB)] (2, 63%) via [{PdI(μ-Cl)(TXPB)}2] (4). Dinuclear 4 could also be prepd. through a comproportionation reaction of Pd(II) complex [PdCl(μ-Cl)(TXPB)] (3) with either [Pd(TXPB)] (2) or [Pd(dba)(TXPB)] (5, dba = dibenzylideneacetone). In complexes 3 and 4, the TXPB ligand is bound to Pd via the phosphine and thioether donors, with a chloride anion bridging between the metal and the borane unit of TXPB. By contrast, the TXPB ligand in 2 is bound to Pd not only via the phosphine and thioether donors but also through a Pd-(η3-BAr3) linkage involving B and the ipso- and ortho-C atoms of one B-Ph ring. The analogous Ni complex, [Ni(TXPB)] (6, 70%) also proved accessible by direct reaction of [Ni(COD)2] with TXPB. In both 2 and 6, short distances (2.02-2.33 Å) between the metal and the B-Cipso-Cortho unit of TXPB and 11B NMR signals shifted 38-39 ppm to lower frequency of free TXPB confirm the presence of a strong M-{η3(BCC)-BAr3} interaction. Reaction of either [Pd2(dvds)3] (dvds = 1,3-divinyltetramethyldisiloxane) with TXPB or complex 2 with dvds resulted in rapid formation of [(κ1-TXPB)Pd(η2:η2-dvds)] (7). The Pt analog of complex 7, [(κ1-TXPB)Pt(η2:η2-dvds)] (8, 59%), was also prepd. by reaction of [Pt(COD)2] with dvds, followed by TXPB. In both 7 and 8, the metal is trigonal planar as a result of η2:η2-coordination to dvds and bonding only to the phosphine group of TXPB. To assess the potential for a ligand with the same structural characteristics as TXPB to coordinate via three η1-interactions, the phosphine analog of TXPB; 2,7-di-tert-butyl-4,5-bis(diphenylphosphino)-9,9-dimethylthioxanthene (Thioxantphos) was prepd., and reaction with [PtX2(COD)] (X = Cl, I) resulted in the clean formation of [PtX(Thioxantphos)]X where X = Cl (9, 66%) and I (10, 72%). These complexes are square planar with the Thioxantphos ligand coordinated through three η1-interactions, confirming the steric accessibility of more traditional κ3-coordination in 4,5-disubstituted thioxanthene ligands such as Thioxantphos and TXPB.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtFaitLrF&md5=2e79a463d7ad27b8e01acf7215cf98a7
    30. 30
      For examples including Ni-complexes, see:Harman, W. H.; Peters, J. C. Reversible H2 Addition across a Nickel-Borane Unit as a Promising Strategy for Catalysis. J. Am. Chem. Soc. 2012, 134, 5080– 5082,  DOI: 10.1021/ja211419t
      30
      Reversible H2 Addition across a Nickel-Borane Unit as a Promising Strategy for Catalysis
      Harman, W. Hill; Peters, Jonas C.
      Journal of the American Chemical Society (2012), 134 (11), 5080-5082CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The synthesis and characterization of Ni complexes of the chelating diphosphine-borane ligands ArB(o-Ph2PC6H4)2 ([ArDPBPh]; Ar = Ph, Mes) is reported. The [ArDPBPh] framework supports pseudo-tetrahedral Ni complexes featuring η2-B,C coordination from the ligand backbone. For the B-Ph deriv., the THF adduct [PhDPBPh]Ni(THF) was characterized by x-ray diffraction and features a very short interaction between Ni and the η2-B,C ligand. For the B-mesityl deriv., the reduced Ni complex [MesDPBPh]Ni is isolated as a pseudo-three-coordinate naked species that undergoes reversible, nearly thermoneutral oxidative addn. of dihydrogen to give a borohydrido-hydride complex of Ni(II) which was characterized in soln. by multinuclear NMR. Also, [MesDPBPh]Ni is an efficient catalyst for the hydrogenation of olefin substrates under mild conditions.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XjtVCqt74%253D&md5=d450313692cf4ae0640e27f9ef688fa1
    31. 31
      Stephan, D. W.; Erker, G. Frustrated Lewis Pair Chemistry: Development and Perspectives. Angew. Chem., Int. Ed. 2015, 54, 6400– 6441,  DOI: 10.1002/anie.201409800
      31
      Frustrated Lewis Pair Chemistry: Development and Perspectives
      Stephan, Douglas W.; Erker, Gerhard
      Angewandte Chemie, International Edition (2015), 54 (22), 6400-6441CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. Frustrated Lewis pairs (FLPs) are combinations of Lewis acids and Lewis bases in soln. that are deterred from strong adduct formation by steric and/or electronic factors. This opens pathways to novel cooperative reactions with added substrates. Small-mol. binding and activation by FLPs has led to the discovery of a variety of new reactions through unprecedented pathways. Hydrogen activation and subsequent manipulation in metal-free catalytic hydrogenations is a frequently obsd. feature of many FLPs. The current state of this young but rapidly expanding field is outlined in this Review and the future directions for its broadening sphere of impact are considered.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXotlGks7g%253D&md5=41885ca09b81140d5c5fc2b6a75f2fe7
    32. 32
      Jupp, A. R.; Stephan, D. W. New Directions for Frustrated Lewis Pair Chemistry. Trends Chem. 2019, 1, 35– 48,  DOI: 10.1016/j.trechm.2019.01.006
      32
      New Directions for Frustrated Lewis Pair Chemistry
      Jupp, Andrew R.; Stephan, Douglas W.
      Trends in Chemistry (2019), 1 (1), 35-48CODEN: TCRHBQ; ISSN:2589-5974. (Cell Press)
      A review. The concerted action of a Lewis acid and base can activate H2 and other small mols. Such frustrated Lewis pairs (FLPs) have garnered much attention and prompted many investigations into the activation of small mols. and catalysis. Although the nature, mechanism of action, and range of FLP systems continues to expand, this concept has also inspired ever-widening chem. Applications in hydrogenation and polymn. catalysis, as well as in synthetic chem., have provided selective processes and metal-free protocols. Heterogeneous FLP catalysts are emerging, and polymeric FLPs offer avenues to unique materials and strategies for sensing and carbon capture. The prospects for further impact of this remarkably simple reaction paradigm are considered.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXit1CqtL%252FP&md5=76c0325cb884a2be4d09dd97a64c8acd
    33. 33
      Yamauchi, Y.; Mondori, Y.; Uetake, Y.; Takeichi, Y.; Kawakita, T.; Sakurai, H.; Ogoshi, S.; Hoshimoto, Y. Reversible Modulation of the Electronic and Spatial Environment around Ni(0) Centers Bearing Multifunctional Carbene Ligands with Triarylaluminum. J. Am. Chem. Soc. 2023, 145, 16938– 16947,  DOI: 10.1021/jacs.3c06267
      33
      Reversible Modulation of the Electronic and Spatial Environment around Ni(0) Centers Bearing Multifunctional Carbene Ligands with Triarylaluminum
      Yamauchi, Yasuhiro; Mondori, Yutaka; Uetake, Yuta; Takeichi, Yasuo; Kawakita, Takahiro; Sakurai, Hidehiro; Ogoshi, Sensuke; Hoshimoto, Yoichi
      Journal of the American Chemical Society (2023), 145 (30), 16938-16947CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Designing and modulating the electronic and spatial environments surrounding metal centers is a crucial issue in a wide range of chem. fields that use organometallic compds. Herein, the authors demonstrate a Lewis-acid-mediated reversible expansion, contraction, and transformation of the spatial environment surrounding Ni(0) centers that bear N-phosphine oxide-substituted N-heterocyclic carbenes (henceforth referred to as (S)PoxIms). Reaction between tetrahedral (syn-κ-C,O-(S)PoxIm)Ni(CO)2 and Al(C6F5)3 smoothly afforded heterobimetallic Ni/Al species such as trigonal-planar {κ-C-Ni(CO)2}(μ-anti-(S)PoxIm){κ-O-Al(C6F5)3} via a complexation-induced rotation of the N-phosphine oxide moieties, while the addn. of 4-dimethylaminopyridine resulted in the quant. regeneration of the former Ni complexes. The corresponding interconversion also occurred between (SPoxIm)Ni(η2:η2-diphenyldivinylsilane) and {κ-C-Ni(η2:η2-diene)}(μ-anti-SPoxIm){κ-O-Al(C6F5)3} via the coordination and dissocn. of Al(C6F5)3. The shape and size of the space around the Ni(0) center was drastically changed through this Lewis-acid-mediated interconversion. Also, the multinuclear NMR, IR, and XAS analyses of the aforementioned carbonyl complexes clarified the details of the changes in the electronic states on the Ni centers; i.e., the electron delocalization was effectively enhanced among the Ni atom and CO ligands in the heterobimetallic Ni/Al species. The results presented in this work thus provide a strategy for reversibly modulating both the electronic and spatial environment of organometallic complexes, in addn. to the well-accepted Lewis-base-mediated ligand-substitution methods.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhsV2itb%252FJ&md5=8bc1e4a313876cb15439e92ddac5a413
    34. 34
      Carden, J. L.; Dasgupta, A.; Melen, R. L. Halogenated triarylboranes: synthesis, properties and applications in catalysis. Chem. Soc. Rev. 2020, 49, 1706– 1725,  DOI: 10.1039/C9CS00769E
      34
      Halogenated triarylboranes: synthesis, properties and applications in catalysis
      Carden, Jamie L.; Dasgupta, Ayan; Melen, Rebecca L.
      Chemical Society Reviews (2020), 49 (6), 1706-1725CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      A review discusses Lewis acidity detn. of boranes and the synthesis of these boranes and examples of how they are being used for catalysis and frustrated Lewis pair (FLP) chem. are explained. Halogenated triarylboranes (BAr3) were known for decades, however it has only been since the surge of interest in main group catalysis that their application as strong Lewis acid catalysts was recognized. This review aims to look past the popular tris(pentafluorophenyl)borane [B(C6F5)3] to the other halogenated triarylboranes, to give a greater breadth of understanding as to how tuning the Lewis acidity of BAr3 by modifications of the aryl rings can lead to improved reactivity.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXjvVKmtbg%253D&md5=1c835b98453c686738c42bd3f67f405f
    35. 35
      Ashley, A. E.; Herrington, T. J.; Wildgoose, G. G.; Zaher, H.; Thompson, A. L.; Rees, N. H.; Krämer, T.; O’hare, D. Separating Electrophilicity and Lewis Acidity: The Synthesis, Characterization, and Electrochemistry of the Electron Deficient Tris(aryl)boranes B(C6F5)3-n(C6Cl5)n (n = 1–3). J. Am. Chem. Soc. 2011, 133, 14727– 14740,  DOI: 10.1021/ja205037t
      35
      Separating electrophilicity and lewis acidity: the synthesis, characterization, and electrochemistry of the electron deficient tris(aryl)boranes B(C6F5)3-n(C6Cl5)n (n = 1-3)
      Ashley, Andrew E.; Herrington, Thomas J.; Wildgoose, Gregory G.; Zaher, Hasna; Thompson, Amber L.; Rees, Nicholas H.; Kramer, Tobias; O'Hare, Dermot
      Journal of the American Chemical Society (2011), 133 (37), 14727-14740CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      A new family of electron-deficient triarylboranes, B(C6F5)3-n(C6Cl5)n (n = 1-3), has been synthesized, permitting an investigation into the steric and electronic effects resulting from the gradual replacement of C6F5 with C6Cl5 ligands. B(C6F5)2(C6Cl5) (3) is accessed via C6Cl5BBr2, itself prepd. from donor-free Zn(C6Cl5)2 and BBr3. Reaction of C6Cl5Li with BCl3 in a Et2O/hexane slurry selectively produced B(C6Cl5)2Cl, which undergoes B-Cl exchange with CuC6F5 to afford B(C6F5)(C6Cl5)2 (5). While 3 forms a complex with H2O, which can be rapidly removed under vacuum or in the presence of mol. sieves, B(C6Cl5)3 (6) is completely stable to refluxing toluene/H2O for several days. Compds. 3, 5, and 6 have been structurally characterized using single crystal x-ray diffraction and represent the first structure detns. for compds. featuring B-C6Cl5 bonds; each exhibits a trigonal planar geometry about B, despite having different ligand sets. The spectroscopic characterization using 11B, 19F, and 13C NMR indicates that the boron center becomes more electron-deficient as n increases. Optimized structures of B(C6F5)3-n(C6Cl5)n (n = 0-3) using d. functional theory (B3LYP/TZVP) are all fully consistent with the exptl. structural data. Computed 11B shielding consts. also replicate the exptl. trend almost quant., and the computed natural charges on the boron center increase in the order n = 0 (0.81) < n = 1 (0.89) < n = 2 (1.02) < n = 3 (1.16), supporting the hypothesis that electrophilicity increases concomitantly with substitution of C6F5 for C6Cl5. The direct soln. cyclic voltammetry of B(C6F5)3 has been obtained for the first time and electrochem. measurements upon the entire series B(C6F5)3-n(C6Cl5)n (n = 0-3) corroborate the spectroscopic data, revealing C6Cl5 to be a more electron-withdrawing group than C6F5, with a ca. +200 mV shift obsd. in the redn. potential per C6F5 group replaced. Conversely, use of the Gutmann-Beckett and Childs' methods to det. Lewis acidity on B(C6F5)3, 3, and 5 showed this property to diminish with increasing C6Cl5 content, which is attributed to the steric effects of the bulky C6Cl5 substituents. This conflict is ascribed to the minimal structural reorganization in the radical anions upon redn. during cyclic voltammetric expts. Redn. of 6 using sodium soln. in THF results in a vivid blue paramagnetic soln. of Na+ [6]·-; the EPR signal of Na+[6]·- is centered at g = 2.002 with a(11B) 10G. Measurements of the exponential decay of the EPR signal (298 K) reveal [6]·- to be considerably more stable than its perfluoro analog.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtVOnsr7J&md5=3e265507590896cdeefef794ad9877aa
    36. 36
      Sakuraba, M.; Hoshimoto, Y. Recent Trends in Triarylborane Chemistry: Diversification of Structures and Reactivity via meta-Substitution of the Aryl Groups. Synthesis 2024, 56, 3421,  DOI: 10.1055/s-0043-1775394
      There is no corresponding record for this reference.
    37. 37
      Braunschweig, H.; Dewhurst, R. D.; Gessner, V. H. Transition metal borylene complexes. Chem. Soc. Rev. 2013, 42, 3197– 3208,  DOI: 10.1039/c3cs35510a
      37
      Transition metal borylene complexes
      Braunschweig, Holger; Dewhurst, Rian D.; Gessner, Viktoria H.
      Chemical Society Reviews (2013), 42 (8), 3197-3208CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      A review. Borylene ligands (:BR) are isolobal to CO and other iconic organometallic ligands. As such, borylene ligands enjoy some parallels to these ligands, but in many ways, their chem. is distinct. This tutorial review gives an introduction to the synthesis, properties and reactivity of the major classes of transition metal borylene complexes, including terminal and bridging examples, pseudoborylenes, and metalloborylenes (borido complexes).
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXksFemsLs%253D&md5=d93a2e913656a836f584b5d88b7c19d8
    38. 38
      Kong, L.; Lu, W.; Yongxin, Y.; Ganguly, R.; Kinjo, R. Formation of Boron–Main-Group Element Bonds by Reactions with a Tricoordinate Organoboron L2PhB: (L = Oxazol-2-ylidene). Inorg. Chem. 2017, 56, 5586– 5593,  DOI: 10.1021/acs.inorgchem.6b02993
      38
      Formation of Boron-Main-Group Element Bonds by Reactions with a Tricoordinate Organoboron L2PhB: (L = Oxazol-2-ylidene)
      Kong, Lingbing; Lu, Wei; Yongxin, Li; Ganguly, Rakesh; Kinjo, Rei
      Inorganic Chemistry (2017), 56 (10), 5586-5593CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      Reactivity of L2PhB: (1; L = 3,4,4-trimethyl-2-oxazolidinylidene) as well as its transition metal (Cr, Fe) complexes toward main group substrates have been systematically examd., which led construction of B-E (E = C, Ga, Cl, H, F, N) bonds. The combination of 1 and triethylborane (Et3B) smoothly captured carbon dioxide (CO2) concomitant with the formation of B-C and B-O bonds. The soft basic boron center in 1 readily reacted with soft acidic gallium trichloride (GaCl3) to afford extremely stable adduct [L2PhBGaCl3] (4) involving a B-Ga bond. Alkylation of neutral tricoordinate organoboron was first achieved by treatment of 1 with dichloromethane (DCM) and Me trifluoromethanesulfonate (MeOTf), both of which afforded ionic species [L2PhBCH2Cl]Cl (5) and [L2PhBMe][OTf] (6), featuring an addnl. B-C bond. Comparatively, redox reactions took place when halides of heavier elements such as germanium dichloride (GeCl2), dichlorophenylphosphine (PhPCl2) and chlorodiphenylbismuth (Ph2BiCl) were employed as substrates, from which cationic species [L2PhBCl]Cl (7) bearing a B-Cl bond was obtained. In addn., reactions of metal complexes [L2PhBM(CO)n] (2, M = Cr, n = 5; 8, M = Fe, n = 4) with cationic electrophiles were investigated. With HOTf and FN(SO2Ph)2, the corresponding ionic species featuring a B-H bond [L2PhBH][OTf] (9), a B-F bond [L2PhBF][N(SO2Ph)2] (10) were formed via a formal electrophilic substitution reaction whereas the reaction of 1 with F•Py-BF4 resulted in the formation of a dicationic boron species [L2PhB(py)][BF4]2 (11) with a B-N bond.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhs1Ois78%253D&md5=4e0ed60dd9d3462b675ecb6e86eee612
    39. 39
      Reineke, M. H.; Sampson, M. D.; Rheingold, A. L.; Kubiak, C. P. Synthesis and Structural Studies of Nickel(0) Tetracarbene Complexes with the Introduction of a New Four-Coordinate Geometric Index, τδ. Inorg. Chem. 2015, 54, 3211– 3217,  DOI: 10.1021/ic502792q
      39
      Synthesis and Structural Studies of Nickel(0) Tetracarbene Complexes with the Introduction of a New Four-Coordinate Geometric Index, τδ
      Reineke, Mark H.; Sampson, Matthew D.; Rheingold, Arnold L.; Kubiak, Clifford P.
      Inorganic Chemistry (2015), 54 (7), 3211-3217CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      The synthesis and characterization of two homoleptic chelating Ni(0) tetracarbene complexes are reported. These are the 1st Group 10 M(0) (M = Ni, Pd, Pt) tetracarbene complexes. These species have geometries intermediate between C2v sawhorse and tetrahedral and show high UV-visible absorption in the 350-600 nm range, with extinction coeffs. (ε) between 5600 and 9400 M-1 cm-1. D. functional theory anal. indicates that this high absorptivity is due to metal-to-ligand charge transfer. To better describe the unusual geometries encountered in these complexes, an adjustment to the popular τ4 index for four-coordinate geometries is introduced to better delineate between sawhorse and distorted tetrahedral geometries.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXkt1Ojsb0%253D&md5=7b81523cd3d0587c779d150ce88825cb
    40. 40
      Holschumacher, D.; Bannenberg, T.; Hrib, C. G.; Jones, P. G.; Tamm, M. Heterolytic Dihydrogen Activation by a Frustrated Carbene-Borane Lewis Pair. Angew. Chem., Int. Ed. 2008, 47, 7428– 7432,  DOI: 10.1002/anie.200802705
      40
      Heterolytic dihydrogen activation by a frustrated carbene-borane Lewis pair
      Holschumacher, Dirk; Bannenberg, Thomas; Hrib, Cristian G.; Jones, Peter G.; Tamm, Matthias
      Angewandte Chemie, International Edition (2008), 47 (39), 7428-7432CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The sterically demanding carbene 1,3-di-tert-butyl-1,3-dihydro-2H-imidazol-2-ylidene and B(C6F5)3, a frustrated Lewis pair, is a viable system for the activation of C-O, H-H, and C-H bonds. However, slow rearrangement to an abnormal carbene-borane adduct allows the irreversible formation of a strong B-C bond and enables this system to circumvent frustration at the expense of its activity. The crystal and mol. structures of imidazoliumyl- and (imidazoliumylbutoxy)boron zwitterions and imidazolium hydrotriarylborate were detd. by x-ray crystallog. Optimized structures and potential energy profiles were calcd. using B3LYP DFT.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXht1Shu7jN&md5=7aab94e9873941ad26d5c28cc1cbf4d7
    41. 41
      Chase, P. A.; Stephan, D. W. Hydrogen and Amine Activation by a Frustrated Lewis Pair of a Bulky N-Heterocyclic Carbene and B(C6F5)3. Angew. Chem., Int. Ed. 2008, 47, 7433– 7437,  DOI: 10.1002/anie.200802596
      41
      Hydrogen and amine activation by a frustrated Lewis pair of a bulky N-heterocyclic carbene and B(C6F5)3
      Chase, Preston A.; Stephan, Douglas W.
      Angewandte Chemie, International Edition (2008), 47 (39), 7433-7437CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The frustrated Lewis pair derived from B(C6F5)3 and the sterically encumbered N-heterocyclic carbene N,N'-tBu2C3H2N2 cleaves dihydrogen heterolytically to give a imidazolium borate, and cleaves amine N-H bonds to form aminoborate salts or aminoboranes.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXht1Shu7jO&md5=2387bf7931cb443e91156ada5c99ffa7
    42. 42
      Choukroun, R.; Lorber, C.; Lepetit, C.; Donnadieu, B. Reactivity of [Cp2Ti(CO)2] and B(C6F5)3: Formation of the Acylborane Complexes [Cp2Ti(CO)(η2-OCB(C6F5)3)] and [Cp2Ti(THF)(η2-OCB(C6F5)3)]. Organometallics 2003, 22, 1995– 1997,  DOI: 10.1021/om030185t
      42
      Reactivity of [Cp2Ti(CO)2] and B(C6F5)3: Formation of the Acylborane Complexes [Cp2Ti(CO)(η2-OCB(C6F5)3)] and [Cp2Ti(THF)(η2-OCB(C6F5)3)]
      Choukroun, Robert; Lorber, Christian; Lepetit, Christine; Donnadieu, Bruno
      Organometallics (2003), 22 (10), 1995-1997CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
      The reaction of [Cp2Ti(CO)2] with B(C6F5)3 leads, surprisingly, as revealed by x-ray structure detn. to the unexpected titana acylborane [Cp2Ti(L)(η2-OCB(C6F5)3)] (1, L = CO, "O-outside" configuration; 2, L = THF, "O-inside" configuration) with the tris(perfluorophenyl)borane, as a Lewis acid, attached to the carbonyl carbon atom. The acylborane picture is strengthened by a theor. calcn. (ELF).
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXis1Ohu7c%253D&md5=a044128936d91ce446ab60a860895069
    43. 43
      Lyngdoh, R. H. D.; Schaefer, H. F.; King, R. B. Metal-Metal (MM) Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc. Chem. Rev. 2018, 118, 11626– 11706,  DOI: 10.1021/acs.chemrev.8b00297
      There is no corresponding record for this reference.
    44. 44
      Shriver, D. F. BASCITY AND REACTIVITY OF METAL CARBONYLS. J. Organomet. Chem. 1975, 94, 259– 271,  DOI: 10.1016/S0022-328X(00)88721-5
      44
      Basicity and reactivity of metal carbonyls
      Shriver, D. F.
      Journal of Organometallic Chemistry (1975), 94 (2), 259-71CODEN: JORCAI; ISSN:0022-328X.
      A review with 45 refs.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE2MXkvFGkt7s%253D&md5=00d222e3f0312df326eb24a531194086
    45. 45
      Gong, J.-K.; Kubiak, C. P. A New Route to the Ni(0) ‘Cradle’ Complex Ni2(μ-CO)(CO)2(PPh2CH2PPh2)2: μ-CO Ligand and Metal-centered Reactivity. Inorg. Chim. Acta 1989, 162, 19– 21,  DOI: 10.1016/S0020-1693(00)83112-6
      45
      A new route to the nickel(0) 'cradle' complex bis[bis(diphenylphosphino)methane](μ-carbonyl)dicarbonyldinickel: μ-carbonyl ligand and metal-centered reactivity
      Gong, Jin Kang; Kubiak, Clifford P.
      Inorganica Chimica Acta (1989), 162 (1), 19-21CODEN: ICHAA3; ISSN:0020-1693.
      Ni2(μ-CO)(CO)2(Ph2PCH2PPh2)2 (I) was prepd. by the reaction of Ni(COD)3 (COD = cyclooctadiene) with (Ph2P)2CH2 and CO in toluene. I reacted with AlR3 (R = Me, Et) to give Ni2(μ-CO)(AlR3)(CO)2(Ph2PCH2PPh2)2 (II). I reacted with HPF6 to give [Ni2(μ-CO)(μ-H)(CO)2(Ph2PCH2PPh2)2]PF6. In II AlR3 is coordinated to the μ-CO ligand. The reaction of I with H+ leads to metal-centered reactivity. The complexes were characterized by IR and 1H NMR spectra.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3cXhslSrtLk%253D&md5=dc976da7896b4573d44f342d0170b7b6
    46. 46
      Bernhardt, E.; Finze, M.; Willner, H.; Lehmann, C. W.; Aubke, F. Salts of the Cobalt(I) Complexes [Co(CO)5]+ and [Co(CO)2(NO)2]+ and the Lewis Acid-Base Adduct [Co2(CO)7CO-B(CF3)3]. Chem.─Eur. J. 2006, 12, 8276– 8283,  DOI: 10.1002/chem.200600210
      46
      Salts of the cobalt(I) complexes [Co(CO)5]+ and [Co(CO)2(NO)2]+ and the Lewis acid-base adduct [Co2(CO)7CO-B(CF3)3]
      Bernhardt, Eduard; Finze, Maik; Willner, Helge; Lehmann, Christian W.; Aubke, Friedhelm
      Chemistry - A European Journal (2006), 12 (32), 8276-8283CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The reaction of [Co2(CO)8] with (CF3)3BCO in hexane leads to the Lewis acid-base adduct [Co2(CO)7CO-B(CF3)3] in high yield. When the reaction was performed in anhyd. HF soln. [Co(CO)5][(CF3)3BF] is isolated. The product contains the 1st example of a homoleptic metal pentacarbonyl cation with 18 valence electrons and a trigonal-bipyramidal structure. Treatment of [Co2(CO)8] or [Co(CO)3NO] with NO+ salts of weakly coordinating anions results in mixed crystals contg. the [Co(CO)5]+/[Co(CO)2(NO)2]+ ions or pure novel [Co(CO)2(NO)2]+ salts, resp. This is a promising route to other new metal carbonyl nitrosyl cations or even homoleptic metal nitrosyl cations. All compds. were characterized by vibrational spectroscopy and by single-crystal x-ray diffraction.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28Xht1ektbjI&md5=b297a89957a5727d18aa421462832e12
    47. 47
      Wade, C. R.; Lin, T.-P.; Nelson, R. C.; Mader, E. A.; Miller, J. T.; Gabbaï, F. P. Synthesis, Structure, and Properties of a T-shaped 14-Electron Stiboranyl-Gold Complex. J. Am. Chem. Soc. 2011, 133, 8948– 8955,  DOI: 10.1021/ja201092g
      47
      Synthesis, Structure, and Properties of a T-Shaped 14-Electron Stiboranyl-Gold Complex
      Wade, Casey R.; Lin, Tzu-Pin; Nelson, Ryan C.; Mader, Elizabeth A.; Miller, Jeffrey T.; Gabbai, Francois P.
      Journal of the American Chemical Society (2011), 133 (23), 8948-8955CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      A cyclic stiboranyl-gold complex I supported by two 1,8-naphthalenediyl linkers has been synthesized and structurally characterized. The gold atom of this complex adopts a T-shaped geometry and is sepd. from the antimony center by only 2.76 Å. Surprisingly, the trivalent gold atom of this complex is involved in an aurophilic interaction, a phenomenon typically only obsd. for monovalent gold complexes. This phenomenon indicates that the stiboranyl ligand possesses strong σ-donating properties making the trivalent gold atom of I electron rich. This view is supported by DFT calcns. as well as Au L3- and Sb K-edge XANES spectra which reveal that I may also be described as an aurate-stibonium deriv. In agreement with this view, complex I shows no reactivity toward the halides Cl-, Br-, and I-. It does, however, rapidly react with F- to form an unprecedented anionic aurate fluorostiborane complex ([2]-) which has been isolated as the tetra-n-butylammonium salt. The increased coordination no. of the antimony center in this anionic complex ([2]-) does not notably affect the Au-Sb sepn. (2.77 Å) or the geometry at the gold atom which remains T-shaped.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXmsFymu7c%253D&md5=5ae295588aac3232d8f3230a0f887858
    48. 48
      Ansmann, N.; Münch, J.; Schorpp, M.; Greb, L. Neutral and Anionic Square Planar Palladium(0) Complexes Stabilized by a Silicon Z-Type Ligand. Angew. Chem., Int. Ed. 2023, 62, e202313636  DOI: 10.1002/anie.202313636
      There is no corresponding record for this reference.
    49. 49
      For examples including Pt-complexes, see:Kameo, H.; Tanaka, Y.; Shimoyama, Y.; Izumi, D.; Matsuzaka, H.; Nakajima, Y.; Lavedan, P.; Le Gac, A.; Bourissou, D. Square-Planar Anionic Pt0 Complexes. Angew. Chem., Int. Ed. 2023, 62, e202301509  DOI: 10.1002/anie.202301509
      There is no corresponding record for this reference.
    50. 50
      Wächtler, E.; Gericke, R.; Block, T.; Pöttgen, R.; Wagler, J. Trivalent Antimony as L-, X-, and Z-Type Ligand: The Full Set of Possible Coordination Modes in Pt-Sb Bonds. Inorg. Chem. 2020, 59, 15541– 15552,  DOI: 10.1021/acs.inorgchem.0c02615
      There is no corresponding record for this reference.
    51. 51
      For examples including Au-complexes, see:Sircoglou, M.; Bontemps, S.; Mercy, M.; Saffon, N.; Takahashi, M.; Bouhadir, G.; Maron, L.; Bourissou, D. Transition-Metal Complexes Featuring Z-Type Ligands: Agreement or Discrepancy between Geometry and dn Configuration?. Angew. Chem., Int. Ed. 2007, 46, 8583– 8586,  DOI: 10.1002/anie.200703518
      51
      Transition-metal complexes featuring Z-type ligands: agreement or discrepancy between geometry and dn configuration?
      Sircoglou, Marie; Bontemps, Sebastien; Mercy, Maxime; Saffon, Nathalie; Takahashi, Masashi; Bouhadir, Ghenwa; Maron, Laurent; Bourissou, Didier
      Angewandte Chemie, International Edition (2007), 46 (45), 8583-8586CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A combined exptl. and theor. study of [AuCl(diphosphanylborane)] complexes featuring short Au-B contacts is reported. The coordination of ambiphilic diphosphanylborane ligands to AuCl provides unusual square-planar Au(I) complexes. Insight is gained on the Au → borane interactions in these complexes through natural bond orbital (NBO) anal. and 197Au Mossbauer spectroscopy.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtl2rsrnK&md5=58e9ebf97b2d45632db20151b9a2b797
    52. 52
      Dimucci, I. M.; Lukens, J. T.; Chatterjee, S.; Carsch, K. M.; Titus, C. J.; Lee, S. J.; Nordlund, D.; Betley, T. A.; MacMillan, S. N.; Lancaster, K. M. The Myth of d8 Copper(III). J. Am. Chem. Soc. 2019, 141, 18508– 18520,  DOI: 10.1021/jacs.9b09016
      52
      The Myth of d8 Copper(III)
      DiMucci, Ida M.; Lukens, James T.; Chatterjee, Sudipta; Carsch, Kurtis M.; Titus, Charles J.; Lee, Sang Jun; Nordlund, Dennis; Betley, Theodore A.; MacMillan, Samantha N.; Lancaster, Kyle M.
      Journal of the American Chemical Society (2019), 141 (46), 18508-18520CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Seventeen Cu complexes with formal oxidn. states ranging from CuI to CuIII are investigated through the use of multiedge X-ray absorption spectroscopy (XAS) and d. functional theory (DFT) calcns. Anal. reveals that the metal-ligand bonding in high-valent, formally CuIII species is extremely covalent, resulting in Cu K-edge and L2,3-edge spectra whose features have energies that complicate phys. oxidn. state assignment. Covalency anal. of the Cu L2,3-edge data reveals that all formally CuIII species have significantly diminished Cu d character in their lowest unoccupied MOs (LUMOs). DFT calcns. provide further validation of the orbital compn. anal., and excellent agreement is found between the calcd. and exptl. results. The finding that Cu has limited capacity to be oxidized necessitates localization of electron hole character on the supporting ligands; consequently, the phys. d8 description for these formally CuIII species is inaccurate. This study provides an alternative explanation for the competence of formally CuIII species in transformations that are traditionally described as metal-centered, 2-electron CuI/CuIII redox processes.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXitFWlu7rJ&md5=a7bb0efcded5f6960961592f4c0a2757
    53. 53
      DiMucci, I. M.; Titus, C. J.; Nordlund, D.; Bour, J. R.; Chong, E.; Grigas, D. P.; Hu, C. H.; Kosobokov, M. D.; Martin, C. D.; Mirica, L. M.; Nebra, N.; Vicic, D. A.; Yorks, L. L.; Yruegas, S.; MacMillan, S. N.; Shearer, J.; Lancaster, K. M. Scrutinizing Formally NiIV centers through the lenses of core spectroscopy, molecular orbital theory, and valence bond theory. Chem. Sci. 2023, 14, 6915– 6929,  DOI: 10.1039/D3SC02001K
      There is no corresponding record for this reference.
    54. 54
      Tran, V. T.; Li, Z. Q.; Apolinar, O.; Derosa, J.; Joannou, M. V.; Wisniewski, S. R.; Eastgate, M. D.; Engle, K. M. Ni(COD)(DQ): An Air-Stable 18-Electron Nickel(0)-Olefin Precatalyst. Angew. Chem., Int. Ed. 2020, 59, 7409– 7413,  DOI: 10.1002/anie.202000124
      54
      Ni(COD)(DQ): An Air-Stable 18-Electron Nickel(0)-Olefin Precatalyst
      Tran, Van T.; Li, Zi-Qi; Apolinar, Omar; Derosa, Joseph; Joannou, Matthew V.; Wisniewski, Steven R.; Eastgate, Martin D.; Engle, Keary M.
      Angewandte Chemie, International Edition (2020), 59 (19), 7409-7413CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      We report that Ni(COD)(DQ) (COD = 1,5-cyclooctadiene, DQ = duroquinone), an air-stable 18-electron complex originally described by Schrauzer in 1962, is a competent precatalyst for a variety of nickel-catalyzed synthetic methods from the literature. Due to its apparent stability, use of Ni(COD)(DQ) as a precatalyst allows reactions to be conveniently performed without use of an inert-atm. glovebox, as demonstrated across several case studies.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXltlelsbo%253D&md5=f9c3b2de5250c2e8109164422aea1ac6
    55. 55
      Hatsui, T.; Kosugi, N. Metal-to-ligand charge transfer in polarized metal L-edge X-ray absorption of Ni and Cu Complexes. J. Electron Spectrosc. Relat. Phenom. 2004, 136, 67– 75,  DOI: 10.1016/j.elspec.2004.02.133
      55
      Metal-to-ligand charge transfer in polarized metal L-edge X-ray absorption of Ni and Cu complexes
      Hatsui, Takaki; Kosugi, Nobuhiro
      Journal of Electron Spectroscopy and Related Phenomena (2004), 136 (1-2), 67-75CODEN: JESRAW; ISSN:0368-2048. (Elsevier Science B.V.)
      Metal L-edge x-ray absorption spectra for Ni and Cu complexes are discussed by studying their linear polarization dependence. The origin of the characteristic bands is revealed to be 1-electron transitions to ligand-centered MOs carrying metal-to-ligand charge transfer (MLCT). These MLCT transitions are related to the electronic structure of the ground state, particularly, the back-donation. Polarized L-edge x-ray absorption spectroscopy is applied to reveal electronic structures of metal complexes with doped hole and Ni-Ni bonding.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXjsl2mtrw%253D&md5=2893907fad1060294c749dd780dc3a0a
    56. 56
      Solomon, E. I.; Hedman, B.; Hodgson, K. O.; Dey, A.; Szilagyi, R. K. Ligand K-Edge X-ray aabsorption spectroscopy: covalency of ligand-metal bonds. Coord. Chem. Rev. 2005, 249, 97– 129,  DOI: 10.1016/j.ccr.2004.03.020
      56
      Ligand K-edge X-ray absorption spectroscopy: covalency of ligand-metal bonds
      Solomon, Edward I.; Hedman, Britt; Hodgson, Keith O.; Dey, Abhishek; Szilagyi, Robert K.
      Coordination Chemistry Reviews (2005), 249 (1-2), 97-129CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
      A review. The ligand K-edge probes the ligand 1s → valence np transitions. These transitions acquire intensity when the ligand is bound to an open shell metal ion. This intensity quantifies the amt. of ligand character in the metal d orbitals, hence the covalency of the ligand-metal bond. In this review the methodol. is developed and applied to Cu proteins, Fe-S sites and Ni dithiolene complexes, as examples. These illustrate the power and impact of this method in evaluating covalency contributions to electron transfer pathways, redn. potentials, H-bond interactions, electron delocalization in mixed-valent systems and small mol. reactivity.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXhtFejs7zI&md5=e308ff93e025768f574c66267d1a680a
    57. 57
      Sarangi, R.; George, S. D. B.; Rudd, D. J.; Szilagyi, R. K.; Ribas, X.; Rovira, C.; Almeida, M.; Hodgson, K. O.; Hedman, B.; Solomon, E. I. Sulfur K-Edge X-ray Absorption Spectroscopy as a Probe of Ligand-Metal Bond Covalency: Metal vs Ligand Oxidation in Copper and Nickel Dithiolene Complexes. J. Am. Chem. Soc. 2007, 129, 2316– 2326,  DOI: 10.1021/ja0665949
      57
      Sulfur K-Edge X-ray Absorption Spectroscopy as a Probe of Ligand-Metal Bond Covalency: Metal vs Ligand Oxidation in Copper and Nickel Dithiolene Complexes
      Sarangi, Ritimukta; DeBeer George, Serena; Rudd, Deanne Jackson; Szilagyi, Robert K.; Ribas, Xavi; Rovira, Concepcio; Almeida, Manuel; Hodgson, Keith O.; Hedman, Britt; Solomon, Edward I.
      Journal of the American Chemical Society (2007), 129 (8), 2316-2326CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      A combination of Cu L-edge and S K-edge X-ray absorption data and d. functional theory (DFT) calcns. has been correlated with 33S ESR superhyperfine results to obtain the dipole integral (Is) for the S 1s→3p transition for the dithiolene ligand maleonitriledithiolate (MNT) in (TBA)2[Cu(MNT)2] (TBA= tetra-n-butylammonium). The results have been combined with the Is of sulfide derived from XPS studies to exptl. obtain a relation between the S 1s→4p transition energy (which reflects the charge on the S atom, QmolS) and the dipole integral over a large range of QmolS. The results show that, for high charges on S, Is can vary from the previously reported Is values, calcd. using data over a limited range of QmolS. A combination of S K-edge and Cu K- and L-edge X-ray absorption data and DFT calcns. has been used to investigate the one-electron oxidn. of [Cu(MNT)2]2- and [Ni(MNT)2]2-. The conversion of [Cu(MNT)2]2- to [Cu(MNT)2]- results in a large change in the charge on the Cu atom in the mol. (QmolCu) and is consistent with a metal-based oxidn. This is accompanied by extensive charge donation from the ligands to compensate the high charge on the Cu in [Cu(MNT)2]- based on the increased S K-edge and decreased Cu L-edge intensity, resp. In contrast, the oxidn. of [Ni(MNT)2]2- to [Ni(MNT)2]- results in a small change in QmolNi, indicating a ligand-based oxidn. consistent with oxidn. of a MO, ψ*SOMO (singly occupied MO), with predominant ligand character.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtlemtb0%253D&md5=77cd3a8074a6cf06f1ee0728ac766b3f

  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacs.4c15892.

    • Full details pertaining to the experimental methods, identification of the compounds, and DFT calculations (PDF)

    • AIM analysis (XLSX)

    • DFT coordinate (XLSX)

    Accession Codes

    Deposition Numbers 2384752–2384760 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.


    Terms & Conditions

    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.