A single
homogeneous nickel(II) complex, supported by the tris(3,5-dimethylpyrazolyl)borate
ligand and 2-hydroxyquinoline ancillary ligand, is shown to catalyze
both acceptorless dehydrogenation of alcohols and hydrogenation of
carbonyl compounds under mild conditions. Products from the catalytic
reactions were isolated with good yields. A mechanistic investigation
highlights the critical role of the 2-hydroxyquinoline ligand in the
catalysis and argues against a stepwise dehydrogenation pathway.