Dinuclear oxidovanadium complexes with dihydrazone ligands derived from diethyl 2,6-dimethylpyridine-3,5-dicarboxylate obtained from Hantzsch reaction; crystal structure and catalytic activity

Abstract

Two new dihydrazone ligands (H₄L¹ and H₄L²) have been prepared from Hantzsch pyridine ester and after characterization by analytical methods, they have been used in the synthesis of oxidovanadium complexes through their reaction with NH₄VO₃ in methanol. The oxidovanadium complexes have been characterized by single crystal X-ray analysis, which revealed that both of them are anionic dinuclear complexes with the general formula of (NH₄)₂[(VO₂)₂L¹]·(CH₃OH)₂(H₂O)_0.33 (1) and (NH₄)₂[(VO₂)₂L²]·(H₂O) (2). These complexes have been used in the oxidation of sulfides by H₂O₂ and the results showed that they can efficiently oxidize sulfides. Temperature, solvent and the ratio of oxidant to sulfide are effective parameters in the selective oxidation of sulfides by 1 and 2 and they can also influence the catalytic activity of these compounds.