Dimeric Ruthenium(II)-NNN Complex Catalysts Bearing a Pyrazolyl-Pyridylamino-Pyridine Ligand for Transfer Hydrogenation of Ketones and Acceptorless Dehydrogenation of Alcohols

Dimeric pincer-type ruthenium(II)-NNN complexes bearing an unsymmetrical pyrazolyl-pyridylamino-pyridine ligand were prepared and characterized by NMR, elemental analysis, and X-ray single crystal structural determination. These complexes exhibited very high catalytic activity for both transfer hydrogenation of ketones and acceptorless dehydrogenation of secondary alcohols, achieving TOF values up to 1.9 × 10 6 h –1 in the transfer hydrogenation of ketones. The high catalytic activity of the Ru(II) complex catalysts is attributed to the presence of the unprotected NH functionality in the ligand and hemilabile unsymmetrical coordination environment around the central metal atoms in the complex.