Anti-Markovnikov terminal and gem-olefin hydrosilylation using a κ ⁴ -diimine nickel catalyst: selectivity for alkene hydrosilylation over ether C-O bond cleavage

The phosphine-substituted α-diimine Ni precursor, ( ^{Ph ₂ PPr} DI)Ni, has been found to catalyze alkene hydrosilylation in the presence of Ph ₂ SiH ₂ with turnover frequencies of up to 124 h ⁻¹ at 25 °C (990 h ⁻¹ at 60 °C). Moreover, the selective hydrosilylation of allylic and vinylic ethers has been demonstrated, even though ( ^{Ph ₂ PPr} DI)Ni is known to catalyze allyl ester C-O bond hydrosilylation. At 70 °C, this catalyst has been found to mediate the hydrosilylation of ten different gem-olefins, with turnover numbers of up to 740 under neat conditions. Prior and current mechanistic observations suggest that alkene hydrosilylation takes place though a Chalk-Harrod mechanism following phosphine donor dissociation.