Synthesis of a series of new ruthenium organometallic complexes derived from pyridine-imine ligands and their catalytic activity in oxidation of secondary alcohols

Reactions of pyridine imines [C5H4N-2-C(H) = N-C6H4-R] [R = H (1), CH3 (2), OMe (3), CF3 (4), Cl (5), Br (6)] with Ru-3(CO)(12) in refluxing toluene gave the corresponding dinuclear ruthenium carbonyl complexes of the type {mu-eta(2)-CH[(2-C5H4N)(N-C6H4-R)]}(2)Ru-2(CO)(4)(mu-CO) [R = H (7); CH3 (8); OMe (9); CF3 (10); Cl (11); Br (12)]. All six novel complexes were separated by chromatography, and fully characterized by elemental analysis, IR, NMR spectroscopy. Molecular structures of 7, 10, 11, and 12 were determined by X-ray crystal diffraction. Further, the catalytic performance of these complexes was also tested. The combination of {mu-eta(2)-CH[(2-C5H4N)(N-C6H4-R)]}(2)Ru-2(CO)(4)(mu-CO) and NMO afforded an efficient catalytic system for the oxidation of a variety secondary alcohols.