Regiodivergent Hydrosilylation of Alkenes at Nickel: Tuning the Selectivity by Complex Stoichiometry and Silane Identity

Herein, we show that nickel silylphosphine complexes are efficient regioselective catalysts for the hydrosilylation of alkenes. Regiospecific or regioselective diphenylsilane hydrosilylation of aromatic and aliphatic alkenes to the linear isomer is catalyzed by complexes [HNi(κ 2 ( P,Si )-Ph 2 PC 6 H 4 -2-CH 2 SiMe 2 )(PPh 3 ) 2 ] ( 1 ), and [HNi(κ 2 ( P,Si )-Ph 2 P-2-C 6 H 4 CH 2 Si i Pr 2 )(PPh 3 )] ( 2 ), while regiospecific formation of the branched hydrosilylation product is obtained upon employment of the bisligated complex [Ni{κ 2 -( P,Si )-Ph 2 P–C 6 H 4 -2-CH 2 SiMe 2 } 2 ] ( 3 ) with phenylsilane. Turnover numbers of up to 10,000 for the linear and 400 for the branched isomers in this study, situate these base-metal catalysts among the best catalysts reported. Mechanistic insights are consistent with nonradical pathways involving nickel hydride intermediates.