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

The phosphine-substituted -diimine Ni precursor, ((2PPrDI)-P-Ph)Ni, has been found to catalyze alkene hydrosilylation in the presence of Ph2SiH2 with turnover frequencies of up to 124 h(-1) at 25 degrees C (990 h(-1) at 60 degrees C). Moreover, the selective hydrosilylation of allylic and vinylic ethers has been demonstrated, even though ((2PPrDI)-P-Ph)Ni is known to catalyze allyl ester C-O bond hydrosilylation. At 70 degrees 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.