Kinetics of ligand substitution reactions in the oxovanadium(IV)–maltol system

The kinetics of the complex formation between oxovanadium(IV) and maltol was studied by the stopped-flow method at 25 °C in 0.2 M KCl. The formation of the bis-complex is about an order of magnitude faster than that of the mono-complex under the same conditions. The results confirm that parallel paths are operative in these reactions via the acid (HA) and base (A−) forms of the ligand. The relevant rate constants were determined and mechanistic implications of the results are also discussed. It is concluded that the oxovanadium(IV) ion can easily form the thermodynamically most favorable complexes in ligand rich environments such as biological liquids.