Ruthenium(II) Complex Catalysts Bearing a Pyridyl-Based Benzimidazolyl–Benzotriazolyl Ligand for Transfer Hydrogenation of Ketones

Abstract

Air- and moisture-stable ruthenium­(II) complexes bearing a unsymmetrical 2-(benzimidazol-2-yl)-6-(benzotriazol-1-yl)­pyridine ligand were synthesized and structurally characterized by NMR analysis and X-ray crystallographic determinations. These complexes have exhibited excellent catalytic activity in the transfer hydrogenation of ketones in refluxing 2-propanol, reaching final TOFs up to 176400 h^–1. The corresponding RuH complex was isolated and is proposed as the catalytically active species by controlled experiments. The high catalytic activity of the Ru­(II) the complex catalysts is attributed to the hemilabile unsymmetrical coordinating environment around the central metal atom in the complexes and presence of a convertible benzimidazolyl NH functionality in the ligand