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.