Vanadium-51 and oxygen-17 nuclear magnetic resonance study of vanadate(V) equilibria and kinetics

Fifteen Years of Dancing with Vanadium

“…Information on these anions is within the area of polyoxometalates and the areas of materials science interested in vanadium oxides. Information is available on the structures of the simple oxovanadates existing in solution [18,26,96]; more than 100 X-ray structures have now been reported for different cation-anion combinations involving some form of the V 10 O 28 6-anion. Information in this area impacting reactions of oxovanadates with ligands has been summarized recently [17], but more structural information is available directly from the Cambridge Crystallographic Data Centre.…”

“…Two decades ago, the nature of the oxovanadates forming in aqueous solution were not well characterized [18,19], and each species reactivity was relatively unexplored under any conditions of interest to life scientists. Spectroscopic studies using 51 V NMR showed that the colorless solutions of oxovanadates above millimolar concentrations at neutral and alkaline pH contain monomer (V 1 ), dimer (V 2 ), tetramer (V 4 ), and pentamer (V 5 ) formed from pure vanadate salts [18].…”

“…The spectroscopic characterization of the oxovanadates by Howarth and coworkers [18,19] and that of alkylated oxovanadates, i.e., vanadate esters, as reported by the Gresser and Tracey team [20][21][22] were key studies in the area of vanadium(V) solution chemistry. The first study showed that both ethylvanadate and vanadate diethyl ester form when vanadate is in the presence of high levels of ethanol at pH 7.5 ( Fig.…”

“…Most kinetic studies have been carried out in acidic aqueous solutions, where the major vanadium(V) species is the VO 2 + (presumably [VO 2 (H 2 O) 4 ] + ) cation [117,118]. Ligand-exchange reactions have also been investigated using NMR spectroscopy [18,119], and for this class of compounds, NMR-based methods have been more informative than absorption spectroscopy as illustrated in Fig. 11 [44,54,60,80].…”

“…Spectroscopic studies using 51 V NMR showed that the colorless solutions of oxovanadates above millimolar concentrations at neutral and alkaline pH contain monomer (V 1 ), dimer (V 2 ), tetramer (V 4 ), and pentamer (V 5 ) formed from pure vanadate salts [18]. At that time, the speciation was less understood and the signal now assigned to V 4 , was believed by some to be a trimer because in some concentration ranges the distinction is not readily made [26][27][28].…”