Published online by Cambridge University Press: 18 March 2011
Tetramethylammonium (TMA) polyoxovanadates have been precipitated from aqueous solutions aroundpH 7. Decavanadate clusters (TMA)4[H2V10O28]•4H2O are formed at room temperature whereas a layered (TMA)[V4O10] mixed valence compound is formed under hydrothermal conditions. 51V NMR spectra recorded on the solution at different temperatures show that upon heating decavanadate clusters are progressively transformed into cyclic [V4O12]4− metavanadates. This suggests that the mixed valence polyoxovanadates are formed via the ring opening polymerization of metavanadate precursors.