Exclusively Ligand-Mediated Catalytic Dehydrogenation of Alcohols

Design of an efficient new catalyst that can mimic the enzymatic pathway for catalytic dehydrogenation of liquid fuels like alcohols is described in this report. The catalyst is a nickel­(II) complex of 2,6-bis­(phenylazo)­pyridine ligand (L), which possesses the above requisite with excellent catalytic efficiencies for controlled dehydrogenation of alcohols using ligand-based redox couple. Mechanistic studies supported by density functional theory calculations revealed that the catalytic cycle involves hydrogen atom transfer via quantum mechanical tunneling with significant <i>k</i>_H/<i>k</i>_D isotope effect of 12.2 ± 0.1 at 300 K. A hydrogenated intermediate compound, [Ni^IICl₂(H₂L)], is isolated and characterized. The results are promising in the context of design of cheap and efficient earth-abundant metal catalyst for alcohol oxidation and hydrogen storage