Exceptionally Efficient Unsymmetrical Ruthenium(II) NNN Complex Catalysts Bearing a Pyridyl-Based Pyrazolyl−Imidazolyl Ligand for Transfer Hydrogenation of Ketones

Rare ruthenium(II) complexes bearing a pyridyl-based pyrazolyl−imidazolyl ligand were synthesized and exhibited exceptionally high catalytic activity in the transfer hydrogenation of ketones in 2-propanol at 82 °C or room temperature, reaching 100% conversion of the substrates and final TOFs up to 7.2 × 105 h−1 with 0.05 mol % catalyst at 82 °C and 55 800 h−1 with 0.1 mol % catalyst at room temperature.