Ru(II)–halide–carbonyl complexes of naphthylazoimidazoles: Synthesis, spectra, electrochemistry, catalytic activity and electronic structure

[Ru(CO)2Cl2(α/β-NaiR)] (1, 2) and [Ru(CO)2I2(α/β-NaiR)] (3, 4) are synthesized by the reaction of [Ru(CO)2Cl2]n or [Ru(CO)4I2] with α/β-NaiR (1-alkyl-2-(naphthyl-α/β-azo)imidazole (α-NaiR/β-NaiR, where, R = Me, CH2CH3 and CH2Ph)) and have been characterized by spectroscopic data. The geometry of the representative complexes [Ru(CO)2Cl2(β-NaiMe)] (2a) and [Ru(CO)2I2(β-NaiEt)] (4b) have been structurally confirmed by X-ray diffraction study. The redox property is examined by electrochemistry. Catalytic activity of these compounds is investigated to the oxidation of PhCH2OH to PhCHO, 2-butanol (C4H9OH) to 2-butanone, 1-phenylethanol (PhC2H4OH) to acetophenone, cyclopentanol (C5H9OH) to cyclopentanone and cyclohexanol to cyclohexanone by N-methylmorpholine-N-oxide (NMO), H2O2 or ButOOH in CH2Cl2 and NMO shows highest yield. The catalytic efficiency is again dependent on Ru–X (X = Cl or I) bond and higher yield is observed for [Ru(CO)2Cl2(α/β-NaiR)] (1, 2). Electronic structure, spectral and redox properties are explained based on DFT and TD-DFT calculations on the representative complexes.