Facile intramolecular silicon–carbon bond activation at Pt0 and PtII centers

Unexpected alkyl isomerization at the silicon ligand of an unsaturated Rh complex: combined experiment and theory

The formation of dimer [(μ-Cl)Rh-(κ3(P,Si,Si)PhP(o-C6H4CH2SiiPr2)(o-C6H4CH2SiiPrnPr))]2 (Rh-3) with an n-propyl group on one of the silicon atoms as a minor product was affected by the reaction of [RhCl(COD)]2 with proligand PhP(o-C6H4CH2SiHiPr2)2, L1. The major product of the reaction was monomeric 14-electron Rh(III) complex [ClRh(κ3(P,Si,Si)PhP(o-C6H4CH2SiiPr2)2)] (Rh-1). Computations revealed that the monomer-dimer equilibrium is shifted toward the monomer with four isopropyl substituents on the two Si atoms of the ligand as in Rh-1; conversely, the dimer is favored with only one n-propyl as in Rh-3, and with less bulky alkyl substituents such as in [ClRh(κ3(P,Si,Si)PhP(o-C6H4CH2SiMe2)2]2 (Rh-2). Computations on the mechanism of formation of Rh-3 directly from [RhCl(COD)]2 are in agreement with the experimental findings and it is found to be less energetic than if stemming from Rh-1. Additionally, a Si-O-Si complex, [μ-Cl-Rh{κ3(P,Si,C)PPh(o-C6H4CH2SiiPrO SiiPr2CH-o-C6H4)}]2, Rh-4, is generated from the reaction of Rh-1 with adventitious water as a result of intramolecular C-H activation.

Metathesis between E-C(spn ) and H-C(sp3 ) σ-Bonds (E=Si, Ge; n=2, 3) on an Osmium-Polyhydride

The silylation of a phosphine of OsH₆(PⁱPr₃)₂ is performed via net‐metathesis between Si−C(spⁿ) and H−C(sp³) σ‐bonds (n=2, 3). Complex OsH₆(PⁱPr₃)₂ activates the Si−H bond of Et₃SiH and Ph₃SiH to give OsH₅(SiR₃)(PⁱPr₃)₂, which yield OsH₄{κ¹‐P,η²‐SiH‐[ⁱPr₂PCH(Me)CH₂SiR₂H]}(PⁱPr₃) and R−H (R=Et, Ph), by displacement of a silyl substituent with a methyl group of a phosphine. Such displacement is a first‐order process, with activation entropy consistent with a rate determining step occurring via a highly ordered transition state. It displays selectivity, releasing the hydrocarbon resulting from the rupture of the weakest Si‐substituent bond, when the silyl ligand bears different substituents. Accordingly, reactions of OsH₆(PⁱPr₃)₂ with dimethylphenylsilane, and 1,1,1,3,5,5,5‐heptamethyltrisiloxane afford OsH₅(SiR₂R′)(PⁱPr₃)₂, which evolve into OsH₄{κ¹‐P,η²‐GeH‐[ⁱPr₂PCH(Me)CH₂SiR₂H]}(PⁱPr₃) (R=Me, OSiMe₃) and R′−H (R′=Ph, Me). Exchange reaction is extended to Et₃GeH. The latter reacts with OsH₆(PⁱPr₃)₂ to give OsH₅(GeEt₃)(PⁱPr₃)₂, which loses ethane to form OsH₄{κ¹‐P,η²‐GeH‐[ⁱPr₂PCH(Me)CH₂GeEt₂H]}(PⁱPr₃).

Facial-Meridional Isomerization and Reductive Elimination in [(R2P-o-C6H4)2N]PtMe3 (R = Ph, iPr)

Treatment of PtMe₃I in tetrahydrofuran with either in situ prepared [R-PNP]Li ([R-PNP]^- = [(R₂P-o-C₆H₄)₂N]^-; R = Ph, iPr) or H[R-PNP] in the presence of triethylamine at room temperature affords quantitatively fac-[R-PNP]PtMe₃. Thermolysis of fac-[R-PNP]PtMe₃ in benzene solutions generates mer-[R-PNP]PtMe₃ and ultimately [R-PNP]PtMe and ethane. Complexes mer-[R-PNP]PtMe₃ represent the first meridional trialkylplatinum(IV) derivatives to date.

Si-C(sp3) bond activation through oxidative addition at a Rh(i) centre

An easy, direct and room temperature silicon-carbon bond activation is reported. The reaction of [RhCl(coe)₂]₂ with the silane Si(Me)₂(o-C₆H₄SMe)₂ in the presence of an halide extractor provokes a Si-CH₃ bond cleavage yielding a cationic silyl-methyl-Rh(iii). In contrast, if the reaction is performed using the Rh(i) bis-alkene dimers, [RhCl(cod)]₂ or [RhCl(nbd)]₂, the Si-CH₃ bond activation does not occur.

Multidentate silyl ligands in transition metal chemistry

This review presents and discusses the use of multidentate silanide ligands in transition metal chemistry depending on their ligand architecture.

Examining the role of Rh/Si cooperation in alkene hydrogenation by a pincer-type [P2Si]Rh complex

A bis(phosphine)/triflatosilyl pincer-type Rh(i) complex can reversibly store one equivalent of H2 across the Si-Rh bond upon triflate migration from silicon to rhodium. The triflatosilyl complex serves as an effective precatalyst for norbornene hydrogenation, but Si-OTf bond cleavage is not implicated in the major catalytic pathway. The combined findings suggest possible strategies for M/Si cooperation in catalytic processes.