Identification of mixed vanadium-tungsten polyoxocomplexes in aqueous solutions by17O and51V NMR

1. In aqueous solutions containing vanadium(V) and tungsten (VI) isopolyanions V3W30195− are formed at pH 7–9 which are isostructural with the isopolyanions VW5O193− and V2W4,O194−. 2. The51V NMR spectra of the salt K6V4W9O40· 24H2O have confirmed the identity of the polyanions in solution and in crystal form and shown the presence of vanadium atoms in tetrahedral and octahedral coordination. 3. All the17O and51V NMR data obtained have confirmed the composition V4W9O406− for the anion of the purple salt and its correspondence to Keggin's structure with vanadium atoms in the central tetrahedral cavity.