Aqueous tungstovanadate equilibria

A combined equilibrium study of tungstovanadates involving potentiometry and V-51, W-183 and O-17 NMR spectroscopy has been able to identify 11 main species, giving their formation Constants and pK(a) values where relevant. Tentative identification was also made of two other non-equilibrium species at lower pH values, in addition to those with a V-centred Keggin structure. The V-51 shifts of the unprotonated hexametalate anions fall into a rational pattern, and the formation constants are all higher than those of the corresponding molybdovanadate species, where comparisons are possible.