A new oxidovanadium(IV) complex containing an O, N-bidentate Schiff base ligand: Synthesis, characterization, crystal structure determination, thermal study and catalytic activity for an oxidative bromination reaction

A new oxidovanadium(IV) schiff base complex (1) containing an ethyl bromide pendant group was synthesized by the reaction of the related bidentate O, N-Schiff base ligand and VO(acac)2 in a 2:1 ratio in methanol, under reflux conditions. The Schiff base ligand and its vanadyl Schiff base complex were characterized by 1H NMR and FT-IR spectra, and CHN analysis. The crystal structure of 1 was also determined by single crystal X-ray analysis. The vanadium center in this structure has a distorted tetragonal pyramidal N2O3 coordination sphere. The Schiff base ligand HL acts as a bidentate ligand by coordinating via the nitrogen atom of the imine group and the oxygen atom of the phenolic group, thereby forming a six-membered chelating ring. There are some non-classical inter- and intra-molecular hydrogen bonds of the type C–H⋯O and C–H⋯Br in 1. The catalytic activity of 1 was studied for the oxidative bromination of 2-nitrophenol as a model substrate. Different reaction parameters were studied in this reaction and the oxidative bromination of some organic compounds by a catalytic amount of 1 showed that it was an effective and selective catalyst under optimal conditions. Thermogravimeric analysis of 1 showed that it decomposed in two stages. In addition, complex 1 thermally decomposed in air at 660 °C and the XRD pattern of the obtained solid showed the formation of V2O5 nanoparticles with an average size of 57 nm.

Graphical abstractA new oxidovanadium(IV) Schiff base complex, VIVOL2, was prepared and characterized by FT-IR spectroscopy, C,H,N and single crystal X-ray analyses. The vanadium(IV) center in this structure has a distorted tetragonal pyramidal N2O3 coordination sphere. The complex was used in the oxidative bromination of organic compounds. The reaction conditions were optimized and the results showed that the complex was a highly active and selective catalyst in this reaction. TGA and thermal decomposition of VOL2 were studied and the latter resulted in the formation of V2O5 nanoparticles.Figure optionsDownload full-size imageDownload as PowerPoint slide