OXYGEN AND VANADIUM EXCHANGE PROCESSES IN LINEAR VANADATE OLIGOMERS

The existence of the linear tri- and tetra-vanadate anions in aqueous solutionhas been confirmed by V-51 and O-17 NMR and potentiometry, yie lding the formation constants. Their resonances are mostly broadened b y an exchange process which is shown by the linewidths and by magnetis ation-transfer experiments to be independent of the monomeric or the d imeric vanadates also present, and also of the solvent oxygens. The br oadenings are not consistent with a simple process of exchange, but in stead reveal the presence of an intermediate, probably cyclic, having a short but not insignificant lifetime. Also, simple proton transfer b etween the oxygens in the aqueous monoprotonated monovanadate anion is sufficiently slow to be detectable by NMR spectroscopy.