OXOVANADIUM(IV) COMPLEXES OF DIPHOSPHATE AND TRIPHOSPHATE

The interaction of oxovanadium(IV) ion with diphosphoric and triphosph oric acids in aqueous solution was investigated over the measurable pH range by means of potentiometry, electronic absorption and EPR measur ements. The results show that both diphosphate and triphosphate, parti ally or fully deprotonated depending on pH, are able to chelate the me tal ion to yield several mononuclear species. With triphosphate, there is no evidence for the formation of a species analogous to the alread y reported and well-characterized trinuclear complex formed by diphosp hate acting as a chelating and bridging ligand through the four unshar ed oxygen atoms.