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*Sm-2-(mu -H)](2) (8) (Cp* = C5Me5) leads to redistribution at silicon, yielding benzene, silane, Ph-2-SiH2, 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*(2); Sm(DMSO)OSiH2OSm(DMSO)Cp*(2) (3). The hard Lewis bases Ph3PO and HMPA (HMPA= (Me2N)(3)PO) 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*Sm-2[OP(NMe2)(2)](HMPA) (6) in low yield. Compound 4 thermally decomposes via liberation of silane to produce Cp*2SmC6H4P(O)Ph-2 (7). In toluene solution, 4 acts as a source of SiH3- in reactions with Mel 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 a-bond metathesis.