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–H2 adducts that catalyze olefin hydrogenation. In contrast, neither the Ni–Al complex nor a single nickel center enables H2 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.