Effect of positional isomerism and vanadium substitution on 51 V magic angle spinning NMR Spectra Of Wells-Dawson polyoxotungstates.

We examined the positional isomerism and vanadium substitution on the 51 V magic angle spinning NMR spectra of potassium salts of vanadium-substituted polyoxotungstates of the Wells-Dawson series. NMR parameters of this class of catalytically active polyoxotungstates effect of are reported. Multiple species, indicative of differences in the local environment at the substitution sites, are observed in solid-state NMR spectra of the di- and tri- substituted complexes in contrast to solution NMR spectra, where single average chemical shift was observed. The quadrupolar and chemical shift anisotropy parameters depend strongly on the position and the degree of the vanadium substitution into the oxoanion core establishing 51 V SATRAS NMR spectroscopy as a sensitive probe of the local electronic environment in these catalytically active solids.