| Three types of pyridyl-based 2,6-(mixed N-heterocycles) ligands and their ruthenium(Ⅱ) and nickel(Ⅱ) complexes were synthesized and structurally characterized.The ruthenium(Ⅱ) complexes were successfully applied in transfer hydrogenation of ketones and aldehydes, exhibiting good to excellent catalytic activity.Unsymmetrical 2-(1-arylimino)-6-(pyrazol-1-yl)pyridines and their ruthenium(Ⅱ) and nickel NNN complexes were synthesized.The Ru(Ⅱ) complex catalysts exhibited good to excellent catalytic activity in the transfer hydrogenation of ketones.At 82℃,99%conversion was achieved for ketones over aperiod of 5 minutes with final TOFs up to 5940 h-1.Ruthenium(Ⅱ) NNN complexes beating a pyridyl-supported pyrazolyl-imidazolyl ligand exhibited exceptionally high catalytic activity in transfer hydrogenation reaction in 2-propanol. At room temperature and in air,98%conversion of the ketone substrates was obtained with final TOFs up to 59400 h-1.At room temperature and in N2,98%conversion was also reached for aldehyde substrates with final TOFs up to 5940 h-1.At 82℃,99%conversion was obtained for the ketone and aldehyde substrates and the final TOFs up to 712800 h-1.Ruthenium(Ⅱ) NNN complexes bearing a pyridyl-supported oxazolinyl-imidazolyl ligand exhibited high catalytic activity in the asymmetric transfer hydrogenation of ketones in 2-propanol.At room temperature using a catalyst loading of 0.1 mol%,ketones were quantitativly convered to acohols with a high enantioselectivity.Within 10 minutes,a variety of aromatic ketoneswere reduced to the corresponding secondary alcohols with97%ee and final TOFs up to 14850 h-1.A ruthenium(Ⅱ) NNN complex bearing 2,6-bis[7,8,8-trimethyl-4,5,6,7-tetrahydro-4,7 -methanoindazol-2-yl]pyridine ligand also exhibited good catalytic activity in the asymmetric transfer hydrogenation of ketones in 2-propanol at 82℃,while the highest enantioselectivity of the corresponding secondary alcohols was only reached 34%ee over a period of 3 minutes. |
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