Tuning Nickel with Lewis Acidic Group 13 Metalloligands for Catalytic Olefin Hydrogenation

A series of bimetallic complexes pairing zero-valent nickel with group 13 M(III) ions is reported. Stronger Ni -> M(III) dative bonds that render Ni more electron-deficient are seen for larger ions (In > Ga > Al). The larger Ga and In ions stabilize rare, nonclassical Ni-H-2 adducts that catalyze olefin hydrogenation. In contrast, neither the Ni-Al complex nor a single nickel center enables H-2 binding or olefin hydrogenation. By comparison of the structures, redox properties, and catalytic activities of the Ni-M series, the electronic and steric effects of the supporting metal ion are elucidated.