Catalytic Hydrosilylation of Alkenes by a Ruthenium Silylene Complex. Evidence for a New Hydrosilylation Mechanism

Novel ruthenium and osmium silylene species containing Si-H bonds have been synthesized and characterized by NMR spectroscopy. The ruthenium complex [Cp*(iPr3P)(H)2Ru=Si(H)Ph.Et2O][B(C6F5)4] catalyzes the hydrosilyation of alkenes with excellent substrate selectivity for primary silanes and exclusive anti-Markovnikov regiochemistry. Evidence for a novel mechanism involving direct addition of an alkene to the silylene Si-H bond is presented.