A theoretical investigation of ruthenium-catalyzed alkene hydrosilation: Evidence to support an exciting new mechanistic proposal

The mechanism of ethylene hydrosilation catalyzed by the ruthenium silylene cation [Cp*(P(i-Pr)3)Ru(H)2(SiH2)-OEt2]+ has been investigated with B3LYP density functional theory. Calculations using the model cation [Cp(PH3)Ru(H)2(SiH2)-OMe2]+ indicate that the most favorable catalytic cycle is the new mechanism proposed by Glaser and Tilley that involves ethylene insertion into a silicon-hydrogen bond remote from the ruthenium center. All other pathways, including those based on Chalk-Harrod and modified Chalk-Harrod mechanisms that include ethylene coordination to ruthenium, are energetically disfavored. Copyright © 2004 American Chemical Society.