Exceptionally Active Assembled Dinuclear Ruthenium(II)-NNN Complex Catalysts for Transfer Hydrogenation of Ketones

Dinuclear ruthenium(II)-NNN complexes were efficiently assembled by means of coordinatively unsaturated 16-electron mononuclear ruthenium(II)-pyrazolyl-imidazolyl-pyridine complex and 4,4′-linked bipyridine ligands. The diruthenium(II)-NNN complex assembled through 4,4′-(CH 2 ) 3 -bipyridine exhibited exceptionally high catalytic activity for the transfer hydrogenation (TH) of ketones in refluxing 2-propanol and reached TOF values up to 1.4 × 10 7 h –1, demonstrating a remarkable cooperative effect from the ruthenium(II)-NNN functionalities.