Intermediates in nickel(0)–phosphine complex catalyzed dehydrogenative silylation of olefins

Nickel(0) complexes 1–4 containing π-coordinated olefin and triphenylphosphine (tricyclohexylphosphine) (starting from Ni(cod)2) were prepared and the X-ray structures of 1 and 2 were resolved. The complexes appeared as efficient catalysts in dehydrogenative silylation of styrene and vinyltris(trimethylsiloxy)silane, but only after prior oxygenation of phosphine ligand. Stoichiometric studies of Ni(0) complexes with substrates showed that the bis(silyl)nickel(II) complex was a key intermediate in both reactions examined. A scheme of catalysis by Ni(0) complex involving olefin insertion into Ni–Si bond, as a crucial step, is presented.