Homoleptic Cobalt(II) Phenoxyimine Complexes for Hydrosilylation of Aldehydes and Ketones without Base Activation of Cobalt(II)

Air-stable, easy to prepare, homoleptic cobalt­(II) complexes bearing pendant-modified phenoxyimine ligands were synthesized and determined. The complexes exhibited high catalytic performance for reducing aldehydes and ketones via catalytic hydrosilylation, where a hydrosilane and a catalytic amount of the cobalt­(II) complex were added under base-free conditions. The reaction proceeded even in the presence of excess water, and excellent functional-group tolerance was observed. Subsequent hydrolysis gave the alcohol in high yields. Moreover, H2O had a critical role in activation of the Co­(II) catalyst with hydrosilane. Several additional results also indicated that the cobalt­(II) center acts as an active catalyst in the hydrosilylation of aldehydes and ketones.