Dimeric rhodium μ-silylene and μ-η2-silyl complexes:: Catalytic silicon-silicon bond formation and x-ray structures of [{Pr(i)2PCH2CH2PPr(i)2}Rh]2(μ-SiRR′)2 (R = R′ = Ph and R = Me, R′ = Ph) and [{Pr(i)2PCH2CH2PPr(i)2}Rh(H)]2(μ-η2-H-SiMe2)2

The stoichiometric and catalytic reactions of secondary silanes with the rhodium hydride bridged dimer [(dippe)Rh](2)(mu-H)(2) (1; dippe = 1,2-bis(diisopropylphosphino)ethane) are described. The reaction of 1 with Ph2SiH2 results in the formation of the bis(mu-silylene) complex [(dippe)Rh](2)(mu-SiPh2)(2) (2a); a similar reaction ensues upon addition of MePhSiH2 or Me(p)TolSiH(2) ((P)Tol =p-tolyl) to 1 except that the bis(silylene) complexes exist as a mixture of cis and trans stereoisomers. Dimethylsilane reacts with 1 to generate the dinuclear complex [(dippe)Rh(H)](2)(mu-eta(2)-SiMe2)(2) (4d). The hydride dimer acts as a catalyst precursor for the dimerization of excess Ph2SiH2 to tetraphenyldisilane (Ph2SiHSiHPh2). A catalytic cycle is proposed that consists of dinuclear intermediates.