Reactions of Hydrosilanes and Olefins in the Presence of Cp₂MCl₂/nBuLi

The Cp₂MCl₂/nBuLi (M = Ti, Zr, Hf) catalyzed reactions of PhMeSiH₂ in the presence of near-stoichiometric quantities of cyclic and acyclic olefins have demonstrated a range of reactions including hydrosilylation of the olefin, isomerization/hydrosilation of internal olefins, dehydrocoupling of the silane to silicon oligomers, and dehydrocoupling of the silane with the olefin to form vinylsilanes. The product which dominates is a function of the metal and the nature of the olefin. Hydrosilation of terminal acyclic olefins and isomerization/hydrosilylation of internal olefins occur with M = Zr. Cyclic olefins promote the formation of silicon oligomers, and cyclooctene and norbornene with M = Ti provide the highest conversion and highest rates, respectively. Dehydrocoupling of the vinyl hydrogen in cyclooctene and the hydrosilane occurs when M = Zr or Hf. The variations in chemistry can be rationalized through the silylmetal, Cp₂M(H)SiPhMeH, and plausible mechanisms for formation of the various products are discussed.