EQUILIBRIA OF VANADYL(IV) TARTRATES IN AQUEOUS SOLUTION ABOVE pH 7

Abstract

Abstract In aqueous solution at pH ∼8, the reaction of binuclear vanadyl(IV) tartrate(4–), (VO)2 (C4 H2 O6)2 4−, with excess tartrate(2–) ligand gives the mononuclear complex, VO(C4 H3 O6)2 4−. Spectral evidence indicates that the product has a trans coordination by two ionized hydroxyl oxygen atoms and structures are proposed. At ionic strengths of 1.00 M (3.00 M) at 298°K, stoichiometric equilibrium constants of 0.34 ± 0.02 M−1 (0.8 ± 0.2 M−1) and 0.054 ± 0.002 M−1 (0.07 ± 0.01 M−1) have been determined for the binuclear-mononuclear reactions in, respectively, the active system, (VO)2 (d-C4 H2 O6)2 4− + 2d-C4 H4 O6 2− ⇆ 2VO(d-C4 H3 O6)2 4−, and the racemic system, (VO)2 (d-C4 H2 O6)(l-C4 H2 O6)4− + 2dl-C3 H4 O6 2− ⇆ 2VO(dl-C4 H3 O6)2 4−. From these experimentally determined equilibrium constants, the equilibrium constant for the interconversion of the active and racemic binuclear complexes has been derived for two different assumptions of the monomeric isomer distribution in the racemic system. Assuming...