Theoretical investigation on copper hydrides catalyzed hydrosilylation reaction of 3-methylcyclohex-2-enone: mechanism and ligands' effect

Abstract

The mechanism of the hydrosilylation reactions of 3-methylcyclohex-2-enone with tetramethyldisiloxane (TMDS) catalyzed by (Ph₃P)CuH and (IPr)CuH has been investigated by DFT. The catalytic cycle is composed of two steps: the addition of the copper hydrides to the CC bond in the substrate, and the regeneration of the copper hydrides assisted by TMDS. The calculations indicate that the catalyst recovery step is the rate-determining step. The assistances of IPr and Ph₃P ligands to the CuH catalysts make the transition state structures compact and stable. The steric bulk of the ligands could help to stabilize the central Cu atom and promote the coordination of the central Cu atom with the substrate. The higher nucleophilicity of the catalysts and the stronger interaction of the ligands with the central Cu atom make the catalysts interact more easily with the substrate. The hydrosilylation reaction proceeds more favorably when catalyzed by (IPr)CuH as compared to (Ph₃P)CuH.