Crystal growth and structure of V2VSe2IVO9;: comparison with V2Te2O9

High quality single crystals of V2Se2O9 have been obtained as a side compound during a study of the CuCl2-V2O5-SeO2 system. V2Se2O9 crystallises in the monoclinic system, space group P2(1)/n with a = 8.0560(2), b = 10.3650(2), c = 8.4500(2) Angstrom, beta = 102.893(2)degrees, Z = 4 and, rho(x) = 3.90 g/cm(3). Full matrix least-squares refinement gave an R = 0.0347 and R-w = 0.0802 using 2232 independent reflections. The structure is built up by very distorted octahedra occupied by V5+ sharing one edge and one apex to form [V4O18](16-). entities interconnected by SeO3E tetrahedra (E designs the 4s(2) lone pair of the Se (IV) cation). V2Se2O9 is not isostructural with V2Te2O9, in which the V5+O6 octahedra share edges to form along [011] infinite chains linked together via Te2O5E2 groups.