Dehydrogenative Coupling of a Tertiary Silane Using Wilkinson's Catalyst

Wilkinson's catalyst [Rh(PPh3)3Cl] results active in the dehydrogenative coupling of the tertiary silane SiMeH(o-C6H4SMe)2 (L1) to give (o-C6H4SMe)2MeSi–SiMe(o-C6H4SMe)2 (L2). The stoichiometric reaction of [Rh(PPh3)3Cl] with L1 affords a new silyl-hydrido-RhIII complex [Rh(H){SiMe(o-C6H4SMe)2}Cl(PPh3)] (1), which results also active in the dehydrocoupling of L1. The unsaturated RhIII compound [Rh(H){SiMe(o-C6H4SMe)2}(PPh3)][BArF4] (2) was synthesized by reaction of 1 with NaBArF4 and shows lower catalytic activity in this process. Compound 2 reacts with a second equivalent of L1 to form [Rh{SiMe(o-C6H4SMe)2}2][BArF4] (3), which is inactive in catalysis. Our results allow proposing 1 as an active species in the catalytic reaction and suggesting the formation of 3 as a deactivation process when the unsaturated compound 2 is used as catalyst.