Molecular structure, characterization and reactivity of dioxo complexes formed by vanadium(V) with α-hydroxycarboxylate ligands

The structure of the dioxovanadium(V) complexes of glycolic, lactic and malic acids Rb2[{VO2(glyc)}2] [glyc=glycolato(2−)] (1), Cs2[{VO2(mal)}2] [mal=malato(2−)] (2), and Cs2[{VO2(lact)}2]·2H2O [lact=lactato(2−)] (3) has been studied by single-crystal X-ray diffraction. In order to assign the features of the peculiar arrangement adopted by these kinds of complexes, the metrical details of these compounds have been examined and compared to the data available in literature for analogous complexes. The reactivity of the compounds has also been studied. In particular, the reduction of the metal ion by a biological reductant like cysteine, relevant to the role of these complexes in the constitution of the cofactor of the active site of vanadium nitrogenase, has been followed by EPR spectroscopy in an aqueous solution. In addition, the effect of peroxo complex formation on the structure of the dinuclear V2O2 cage has been analyzed by comparison with previously published results.