MECHANISM OF A COBALT(III)-CATALYZED OLEFIN HYDROSILATION REACTION - DIRECT EVIDENCE FOR A SILYL MIGRATION PATHWAY

The electrophilic Co(III) complex [Cp*(P(OMe)3)CoCH2CH2-mu-H]+ BAr'4- (1; BAr'4- = B[3,5-(CF3)2C6H3]4-) has been demonstrated to be an efficient catalyst for the regiospecific hydrosilation of 1-hexene. The spectroscopic detection of the catalyst resting state species [Cp*(P(OMe)3)CoCH(Bu)CH(SiEt3)-mu-H]+ (2) in solutions of working catalyst systems has provided direct evidence for a silyl migration pathway. The spectroscopic detection of [Cp*(P(OMe)3)CoCH2CH-{(CH2)4SiEt3}-mu-H]+ (6), along with supporting kinetics and deuterium labeling experiments, established the turnover-limiting step as the isomerization of 2 to 6.