Synthesis of Sm−SiH₃ Complexes via σ-Bond Metathesis of the Si−C Bond of Phenylsilane

Reaction of PhSiH₃ with the samarium complexes Cp*₂SmCH(SiMe₃)₂ (1) and [Cp*₂Sm(μ-H)]₂ (8) (Cp* = C₅Me₅) leads to redistribution at silicon, yielding benzene, silane, Ph₂SiH₂, Ph₃SiH, and dehydrocoupling products. Cleavage of the Si−C bond of PhSiH₃ is accompanied by formation of the lanthanide hydrosilyl complex [Cp*₂SmSiH₃]₃ (2). Complex 2 activates the S−O bond of dimethyl sulfoxide (DMSO) to form the bridged species Cp*₂Sm(DMSO)OSiH₂OSm(DMSO)Cp*₂ (3). The hard Lewis bases Ph₃PO and HMPA (HMPA = (Me₂N)₃PO) react with 2 to produce the base adducts Cp*₂SmSiH₃(OPPh₃) (4) and Cp*₂SmSiH₃(HMPA) (5), respectively. Complex 5 thermally decomposes, although not cleanly, to produce Cp*₂Sm[OP(NMe₂)₂](HMPA) (6) in low yield. Compound 4 thermally decomposes via liberation of silane to produce (7). In toluene solution, 4 acts as a source of SiH₃^- in reactions with MeI and benzophenone, producing Cp*₂SmI(OPPh₃) (9) and Cp*₂SmOCPh₂(SiH₃) (10), respectively. The high reactivity of 8 toward a stable Si−C bond is discussed in terms of possible mechanisms for this σ-bond metathesis.