Room-temperature structures of oxocopper(II) vanadate(V) hydrates, Cu3V2O8(H2O) and CuV2O6(H2O)2

Cu3V2O8(H2O), Mr=438.51, monoclinic, P21/m, a=7.444 (1), b=6.658 (1), c=7.759 (1) A, β=93.57 (1)deg, V=383.8(2) A3, Z=2, Dx=3.20 Mg m-3, Mo Kα, λ=0.71069 A, μ=10.5 mm-1, F(000)=414.0, R=0.047 for 1307 unique reflections. CuV2O6(H2O)2, Mr=297.47, monoclinic, P2/c, a=5.617 (1), b=5.595 (1), c=11.333 (2)A, β=91.04 (1)deg, V=356.1 (2) A3, Z=2, Dx=2.77 Mg m-3, Mo Kα, λ=0.71069 A, μ=5.4 mm-1, F(000)=286, R=0.045 for 1355 unique reflections. Crystal hydrothermal growth was from Cu2O and NH4VO3 in a 2.5 M NH4HF2 solution. In Cu3V2O8(H2O), copper atoms adopt either a square planar or a fivefold prismatic coordination. Dimeric entities are formed by edge sharing CuO5 and CuO4(H2O) polyhedra. These groups are linked by CuO4 square planes and by pyrovanadate (V2O7)4- di-tetrahedra. The structure of CuV2O6(H2O) consists of infinite chains of [VO3/2O]2n tetrahedra connected by isolated CuO2/2(H2O)2 square planes. In both structures, the location of the oxygen of water molecules can be predicted by valence bond analyisis. (orig.)