Synthesis and Crystal Structure of an Oxovanadium(IV) Complex with a Pyrazolone Ligand and Its Use as a Heterogeneous Catalyst for the Oxidation of Styrene under Mild Conditions

1-Phenyl-3-methyl-4-touloyl-5-pyrazolone (ligand) was synthesized and used to prepare an oxovanadium-(IV) complex. The complex was characterized by single-crystal X-ray analysis and various spectroscopic techniques. The single-crystal X-ray analysis of the complex shows that the ligands are coordinated in a syn configuration to each other and create a distorted octahedral environment around the metal ion. A heterogeneous catalyst comprising an oxovanadium(IV) complex and hydrous zirconia was synthesized, characterized by various physicochemical techniques, and successfully used for the solvent-free oxidation of styrene. The influence of the reaction parameters (percent loading, molar ratio of the substrate to H2O2, amount of catalyst, and reaction time) was studied. The catalyst was reused three times without any significant loss in the catalytic activity.