Ruthenium Complex Catalysts Supported by a Bis(trifluoromethyl)pyrazolyl–Pyridyl-Based NNN Ligand for Transfer Hydrogenation of Ketones

Ru­(III) and Ru­(II) complexes bearing a tridentate 2-(3′,5′-dimethylpyrazol-1′-yl)-6-(3″,5″-bis­(trifluoromethyl)­pyrazol-1″-yl)­pyridine or 2-(benzimidazol-2′-yl)-6-(3″,5″-bis­(trifluoromethyl)­pyrazol-1″-yl)­pyridine ligand were synthesized and applied to the transfer hydrogenation of ketones. The Ru­(II) complex was structurally confirmed by the X-ray crystallographic analysis and achieved up to 2150 turnover numbers and final TOFs up to 29700 h^–1 in the transfer hydrogenation of ketones. The benzimidazolyl moiety with an unprotected NH functionality in the ligand exhibited an enhancement effect on the catalytic activity of its RuCl₃ complex in the ketone reduction reactions, reaching a final TOF value up to 35640 h^–1. The controlled experiments have revealed that the compatibility of the trifluoromethylated pyrazolyl and unprotected benzimidazolyl is crucial for the establishment of the highly active catalytic system

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

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