Structures of two new polymorphic forms of hexavalent tungsten oxide phosphates

Two new modifications of tungsten oxide phosphates, WOP2O7(o) and W2O3(PO4) (2)(o), were prepared, and their structures were determined by single cryst al X-ray techniques. WOP2O7(o) crystallizes in the orthorhombic system, spa ce group Pnma (No. 62) with a = 16.662(2), b = 5.147(2), 6.612(4) Angstrom. The structure was refined to an R factor of 0.028 (R-w = 0.022). The compo und has a layered structure, where the layers are not bridged. Diphosphate group has a terminal oxygen atom bonded only with a phosphorus atom. W2O3(P O4)(2)(o) also crystallizes in the orthorhombic system, space group Pnma (N o, 62) with a = 15,683(1), b = 6,249(1), c = 7.934(1) Angstrom. The refinem ent yielded R = 0.019 (R-w = 0.016). The structure is composed of dioctahed ral W2O11 groups and PO4 groups to form a three-dimensional network. (C) 19 99 Academic Press.