Cu(<scp>i</scp>)–SNS complexes for outer-sphere hydroboration and hydrosilylation of carbonyls

Elsby, Matthew R.; Baker, R. Tom

doi:10.1039/c9cc07266g

Cited by 22 publications

(30 citation statements)

References 39 publications

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“…The replacement of PNP pincer ligands with SNS ligands that contain more weakly σ-donating thioether groups in place of the phosphine donors may be a useful approach to lowering the electron density at the metal. In fact, SNS pincer ligands have already been used to support base metal , and palladium , catalysts due to their relative air stability, facile synthesis, and potential hemilability compared to the PNP ligand platform. For example, palladium catalysts with either pyridyl or aliphatic SNS ligands can facilitate cross-coupling reactions that are proposed to involve homogeneous or heterogeneous active species.…”

Section: Introductionmentioning

confidence: 99%

Comparative Coordination Chemistry of PNP and SNS Pincer Ruthenium Complexes

et al. 2021

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Ruthenium carbonyl complexes supported by PNP pincer ligands are prominent catalysts for a range of hydrogenation and dehydrogenation reactions. Recently, Ru complexes with cheaper, more air stable SNS pincer ligands have emerged as attractive alternatives for the development of improved catalysts. However, there is currently a paucity of information on how the replacement of the phosphine donors in PNP ligands with the sulfur donors in SNS ligands influences the synthesis, structure, and electronic properties of the resulting metal complexes. Herein, the coordination chemistry of a series of Ru carbonyl complexes with SNS pincer ligands has been systematically compared with related PNP-ligated species. Three different SNS pincer ligands were explored including a pyridyl based NC 5 H 3 {CH 2 (S t Bu)} 2 ligand and two aliphatic ligands, HN{CH 2 CH 2 (S t Bu)} 2 and NCH 3 {CH 2 CH 2 (S t Bu)} 2 , along with different combinations of monodentate ancillary ligands. The geometric structures of the SNS and PNP Ru complexes were studied using NMR spectroscopy and X-ray crystallography. Additionally, the redox properties and electronic structures of these complexes were probed through a combination of cyclic voltammetry and DFT calculations. Overall, differences between SNS and PNP complexes extend well beyond simply modulating inductive donation to the metal and include changes in synthetic outcomes, as well as variations in geometry that impact redox behavior. Our study reveals fundamental information about the coordination chemistry of the SNS ligand, which may aid in interpreting catalytic results.

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Section: Introductionmentioning

confidence: 99%

Comparative Coordination Chemistry of PNP and SNS Pincer Ruthenium Complexes

et al. 2021

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“…To our knowledge, there are only two examples on the hydroboration of ketones catalyzed by molecular zinc hydrides (Figure D,E). , It should be noted that no zinc catalysts are available in literature, which performs for both hydrosilylation and hydroboration of many ketones (bifunctional), except D and E, which are limited to only one substrate. However, very recently, the Baker group reported a copper-based catalyst for hydroboration and hydrosilylation of carbonyls …”

Section: Introductionmentioning

confidence: 99%

Zinc Hydride-Catalyzed Hydrofuntionalization of Ketones

et al. 2020

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Three new dimeric bis-guanidinate zinc(II) alkyl, halide, and hydride complexes [LZnEt] 2 (1), [LZnI] 2 (2) and [LZnH] 2 (3) were prepared. Compound 3 was successfully employed for the hydrosilylation and hydroboration of a vast number of ketones. The catalytic performance of 3 in the hydroboration of acetophenone exhibits a turnover frequency, reaching up to 5800 h–1, outperforming that of reported zinc hydride catalysts. Notably, both intra- and intermolecular chemoselective hydrosilylation and hydroboration reactions have been investigated.

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“…14 In contrast, copper complexes with an N-heterocyclic carbene ancillary ligand showed κ 2 -SNS Me binding with the thiolate complex also serving as an efficient (0.5 mol %, RT) outer-sphere carbonyl hydroboration catalyst (Scheme 1C). 16 In another finding relevant to this work, we showed that electron-rich ancillary ligands led to selective C aryl −S bond cleavage with subsequent formation of a coordinated dianionic CNS pincer ligand (Scheme 2). 15,20 For nickel, there are three relevant previous reports.…”

Section: ■ Introductionmentioning

confidence: 68%

“…Transition metal complexes bearing “pincer” ligands tend to exhibit improved thermal stability, reactivity, and catalytic activity/selectivity when compared to their monodentate analogs. − Inspired by a plethora of multiple N,S coordination geometries in metallo-enzymes − and their synthetic models, , we have been preparing new first row metal SNS complexes (Figure ) − in order to assess and compare the roles of “hard” amido and “soft” thiolate donors as cooperative ligands in catalysis …”

Section: Introductionmentioning

confidence: 99%

“…The latter contains a redox-active ligand and proved to be an efficient and selective catalyst for hydroboration of aldehydes . In contrast, copper complexes with an N -heterocyclic carbene ancillary ligand showed κ 2 -SNS Me binding with the thiolate complex also serving as an efficient (0.5 mol %, RT) outer-sphere carbonyl hydroboration catalyst (Scheme C) …”

Section: Introductionmentioning

confidence: 99%

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Nickel(II)-SNS Thiolate Complexes: Reactivity and Solution Dynamics

et al. 2021

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Nickel coordination chemistry with a biomimetic thiolate-imine-thioether SNSMe ligand is accompanied by diverse reactivity and multidentate ligand dynamics. Reaction of Ni(acac)2 with 2 equiv of 2-(methylthio)-phenyl-benzothiazolidine (MPB) affords the bis(arylimino-phenylene-thiolate) complex Ni(κ2-SNSMe)2 (1; acac = acetylacetonate). Thermolysis of 1 in refluxing toluene is accompanied by imine C–C bond formation, yielding [Ni(N2S2)] (2) with a redox-active ligand. Protonation of 1 with NHTf2 at a low temperature released 1 equiv of MPB, yielding crystals of the dimeric dication {[Ni(μ-κ3-SNSMe)]2}(NTf2)2 (3; Tf = SO2CF3) in high yield. In contrast, the same reaction at room temperature gave also paramagnetic complexes {Ni[μ-Ni(κ3-SNSMe)2]2}(NTf2)2 (4) and {Ni[μ-Ni(κ3-SNSMe)2]3}(NTf2)2 (5) that feature coordination of two or three pseudo-octahedral, paramagnetic Ni(κ3-SNSMe)2 units to a central Ni(II) dication via thiolate bridges. Remarkably, dissolution of 3 in a variety of solvents, including weakly coordinating CH2Cl2, rapidly generates a mixture of 4 and Ni(NTf)2. Treatment of this mixture with Lewis bases L gave high yields of dimers {[Ni(μ-κ3-SNSMe)L]2}(NTf2)2 for L = CNXylyl (6a) and {[Ni(μ-κ3-SNSMe)]2(μ-dmpm)}(NTf2)2 (6b; dmpm = bis(dimethylphosphino)methane) or monomers [Ni(κ3-SNSMe)L](NTf2) for L = PMe3 (7a) and P(OMe)3 (7b). Addition of 2 equiv of the strong donor N-heterocyclic carbene ligand, IPr, to 3, however, led to thioether demethylation, affording neutral dithiolate complex Ni(κ3-SNS)(IPr) (8). Reaction products were characterized by NMR and mass spectrometry and complexes 1–5, 6a, 6b, 7a, and 8 by single-crystal X-ray diffraction.

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Cu(i)–SNS complexes for outer-sphere hydroboration and hydrosilylation of carbonyls

Abstract: Two new NHC–Cu(i)-[κ2-SNS] complexes were synthesized to directly compare the bifunctional catalytic activity of a hard amido vs. a soft thiolate donor.

Cited by 22 publications

References 39 publications

Comparative Coordination Chemistry of PNP and SNS Pincer Ruthenium Complexes

Comparative Coordination Chemistry of PNP and SNS Pincer Ruthenium Complexes

Zinc Hydride-Catalyzed Hydrofuntionalization of Ketones

Nickel(II)-SNS Thiolate Complexes: Reactivity and Solution Dynamics

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