NEUTRON AND X-RAY STRUCTURAL CHARACTERIZATION OF THE HEXAAQUAVANADIUM(II) COMPOUND VSO4.7H2O

The title compound, for which crystals are more reactive toward oxygen than the chemically similar compound VSO4.6H(2)O, has been prepared a s large single crystals and characterized by both X-ray diffraction at room temperature and neutron diffraction at 11-16 K. VSO4.7H(2)O crys tallizes in the monoclinic space group P2(1)/c, Z = 4, with the follow ing cell dimensions, where in each case the room temperature X-ray val ue is given first followed by the 11-16 K neutron value: a = 14.130(3) , 14.013(2) Angstrom; b = 6.501(1), 6.481(1) Angstrom; c = 11.017(2), 10.981(2) Angstrom; beta = 105.64(2), 105.39(1)degrees; V = 974.5(3), 961.5(3) Angstrom(3). The structure was refined to residuals of R = 0. 0289 and 0.0766 and quality of fit = 1.047 and 1.427 for X-ray and neu tron data, respectively. It consists of two independent centrosymmetri c V(H2O)(6)(2+) ions connected to a sulfate ion and an interstitial wa ter molecule by an extensive network of hydrogen bonds. The room tempe rature and low-temperature structures are qualitatively identical. Eac h hydrogen atom is involved in a hydrogen bond. The network of hydroge n bonds is implicated in the stability of VSO4.7H(2)O in the solid sta te in dry surroundings.