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

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.