New oxovanadium and dioxomolybdenum complexes as catalysts for sulfoxidation: experimental and theoretical investigations of E and Z isomers of ONO tridentate Schiff base ligand

A new ONO-tridentate Schiff base ligand (H2L) derived by the condensation of nicotinic hydrazide with 5-chlorosalicylaldehyde has been prepared and characterized by combustion analysis (CHN), FT-IR and multinuclear (H-1 and C-13) NMR spectroscopy. The crystalline nature and molecular structure of the ligand were confirmed by single-crystal X-ray diffraction analysis. Furthermore, the optimized structural parameters of the four possible configurations of the ligand including Z and E stereoisomers each containing two tautomeric forms (enol and keto) have also been investigated. The theoretical parameters were calculated by performing the DFT method using the B3LYP/Def2-TZVP level of theory. In addition to this, dioxomolybdenum(VI) (MoO2L) and oxovanadium(V) (VOL) complexes with the entitled Schiff base ligand have also been prepared and characterized by different techniques. Then, the catalytic efficiencies of synthesized VOL and MoO2L complexes were also explored for the oxidation of sulfides using 30% aqueous H2O2 as a source of oxygen. These homogeneous catalysts showed excellent catalytic activities in the oxidation of both aromatic and aliphatic sulfides.

Automated summary

A new ONO-tridentate Schiff base ligand was synthesized and characterized, with its molecular structure further investigated. Additionally, the catalytic efficiencies of the ligand's complexes with dioxomolybdenum(VI) and oxovanadium(V) were explored for sulfide oxidation. The homogeneous catalysts exhibited excellent catalytic activities for both aromatic and aliphatic sulfides oxidation using aqueous H2O2 as the oxygen source.