Ruthenium carbonyl complexes supported by pyridine-alkoxide ligands: synthesis, structure and catalytic oxidation of secondary alcohols

Five novel trinuclear ruthenium complexes [[PyCHC(RC6H4)O]2Ru3(CO)8] [R = 4-OMe (6), 4-Br (7), 4-CF3 (8)] and [[PyCH2CH(RC6H4)O]2Ru3(CO)8] [R = 2-Br (9), 2-CF3 (10)], were synthesized by treating Ru3(CO)12 with two equivalents of the corresponding pyridine-alcohols PyCH2CH(RC6H4)OH [1–5, R = 4-OMe, 4-Br, 4-CF3, 2-Br and 2-CF3] in refluxing toluene. The structures of 6–10 were fully characterized by IR and NMR spectroscopy, elemental analysis and single-crystal X-ray diffraction. They were found to be efficient catalysts for the oxidation of secondary alcohols by NMO, giving the corresponding ketones in good to excellent yields within 15 min, of which [PyCHC(4-OCH3C6H4)O]2Ru3(CO)8 (6) is the best.