Chapter 7: Vanadium-aroylhydrazone Catalysed Oxidations

Metal–ligand cooperation can be an important feature for a metal complex to act as a catalyst. Vanadium complexes in high oxidation sates (IV or V) in the presence of a suitable oxidant (such as, H₂O₂, ^tBuOOH or O₂) can play a significant role in oxidation catalysis under mild conditions. Aroylhydrazone ligands can stabilise vanadium in high oxidation states and adopt different coordination modes. In some cases, they can exhibit redox non-innocent behaviour in the complexes. In this chapter, vanadium compounds based on such ligands and their role in various catalytic oxidation reactions (oxidation of alkanes and alcohols, epoxidations, oxidative brominations, etc.) are discussed. The effects of other parameters, e.g., catalyst amount, time and additive (as promoter) are also discussed. The proposed mechanisms in various oxidation processes are illustrated as well.