Mechanism of olefin hydrosilylation catalyzed by ruCI2(CO)2(PPh3)2

Density functional theory (DFT) was used to explore the different mechanistic possibilities for the hydrosilylation reaction between methyldimethoxysilane and methylvinyldimethoxysilane catalyzed by the Ru(II) complex dicarbonyldichlorobis(triphenylphosphine)ruthenium(II) (A1). Reaction enthalpy profiles of the Chalk−Harrod, modified Chalk−Harrod, and σ-bond metathesis mechanisms were computed for several different active forms of A1. A total of 10 different pathways with different catalytic cycles and different induction steps were compared. We predict that a σ-bond metathesis mechanism involving the formation of a hydride analogue of A1 is most favored, in contrast to the commonly accepted Chalk−Harrod mechanism of hydrosilylation. The B3LYP-calculated activation energy within the catalytic cycle (ΔHact = 21.8 kcal/mol) is small enough to make A1 a reasonable catalyst for this reaction under the normally applied experimental conditions