Ruthenium(III) complexes with tetradentate NSNO donor ligand: Synthesis, electronic structure, catalytic activity and DFT calculation

The ruthenium(III) complexes, cis-(Cl,Cl)-[Ru(L)Cl2] (1) and trans-(Cl,Cl)-[Ru(L)Cl2] (2) with NSNO donor azo functionalized ligand (HL) have been synthesized and characterized by several spectroscopic techniques. Geometry of cis-(Cl,Cl)-[Ru(L)Cl2] (1) has been confirmed by single crystal X-ray study. X-ray structure of 1 suggests pseudo octahedral geometry around Ru with cis-(Cl,Cl) arrangement. Reversible Ru(III)/Ru(II) reduction couple along with irreversible Ru(III)/Ru(IV) oxidation has been observed for the complexes. The complexes catalyze the oxidation of alcohols to aldehydes and ketones in presence of NMO as co-oxidant with moderate to high yields. The electronic structure and solution spectra of the complexes have been supported by DFT and TDDFT calculations.