Ruthenium carbonyl complexes of 3-(2-(methylthio)phenylazo)-4-hydroxy-3-penten-2-one: Synthesis, spectral characterization, electronic structure and catalytic activity

The complexes with general formula cis-(CO)-trans-(X)-[Ru(CO)2(HL)X2] (where X = Cl (1) and I (2)) have been synthesized by the reaction of 3-(2-(methylthio) phenylazo)-4-hydroxy-3-penten-2-one (HL) with ruthenium carbonyls, [Ru(CO)2Cl2]n/[Ru(CO)4I2]. The proposed geometry of the complexes has been supported by elemental and mass analysis abetted with several spectroscopic techniques. The complexes exhibit a quasi-reversible one electron Ru(II)/Ru(III) oxidation couple at 0.88–1.12 V along with ligand based reduction in cyclic voltammetric study. The electronic structure of the complexes has been explained by quantum mechanical calculations by DFT/B3LYP method. Catalytic activities of the compounds are investigated by the oxidation of primary and secondary alcohols to the respective aldehydes and ketones with moderate to high conversions in presence of N-methylmorpholine-N-oxide (NMO) as co-oxidant.