Direct Hydrogenation of Sterically Hindered, Unactivated Alkenes Catalyzed by Phosphino(silyl)‐Nickel Complexes

Readily accessible (PSi)Ni(II)‐benzyl complexes supported by bidentate phosphino(silyl) ligation were found to be effective pre‐catalysts for the direct hydrogenation of a variety of highly sterically hindered, unfunctionalized alkenes under relatively mild conditions (2.5‐5 mol% Ni, 10 atm H2, 50 °C) and without the need for additional additives or activator species. A range of substrates, including di‐, tri‐, and tetra‐substituted alkenes were evaluated in this regard and afforded good to moderate yields. Substrates featuring α,β‐unsaturated carbonyl functionality were also readily hydrogenated with no evidence for reduction of carbonyl or ester C−O functionalities. Deuteration experiments highlight the occurrence of chain walking which occurs in the background of the reported catalytic chemistry. Readily accessible (PSi)Ni(II)‐benzyl complexes were found to be effective pre‐catalysts for the hydrogenation of a variety of highly sterically hindered, unfunctionalized alkenes without the need for additional additives or activator species. A range of substrates, including di‐, tri‐, and tetra‐substituted alkenes were evaluated in this regard, with good to moderate yields obtained.