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

Abstract [Ru(CO) 2 Cl 2 (α/β-NaiR)] ( 1 , 2 ) and [Ru(CO) 2 I 2 (α/β-NaiR)] ( 3 , 4 ) are synthesized by the reaction of [Ru(CO) 2 Cl 2 ] n or [Ru(CO) 4 I 2 ] with α/β-NaiR (1-alkyl-2-(naphthyl-α/β-azo)imidazole (α-NaiR/β-NaiR, where, R = Me, CH 2 CH 3 and CH 2 Ph)) and have been characterized by spectroscopic data. The geometry of the representative complexes [Ru(CO) 2 Cl 2 (β-NaiMe)] ( 2a ) and [Ru(CO) 2 I 2 (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 PhCH 2 OH to PhCHO, 2-butanol (C 4 H 9 OH) to 2-butanone, 1-phenylethanol (PhC 2 H 4 OH) to acetophenone, cyclopentanol (C 5 H 9 OH) to cyclopentanone and cyclohexanol to cyclohexanone by N-methylmorpholine-N-oxide (NMO), H 2 O 2 or Bu t OOH in CH 2 Cl 2 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) 2 Cl 2 (α/β-NaiR)] ( 1 , 2 ). Electronic structure, spectral and redox properties are explained based on DFT and TD-DFT calculations on the representative complexes.