Crystal structure of a new sodium vanadyl(IV) fluoride phosphate Na3{V2O2F[PO4]2}

The title compound has been prepared by hydrothermal synthesis and its crystal structure was determined by single crystal X-ray diffraction: space group I4/mmm, a = 6.3856(2), c = 10.6119(9) Angstrom, wR(2) = 0.039, R = 0.016. The crystal structure of Na-3{V2O2F[PO4](2)} is formed by layers of alternating [VO5F] octahedra and [PO4] tetrahedra sharing 0 vertices parallel to the ab plane. Along the c direction the V octahedra are joined pairwise through common F vertices in the inversion centres. The sixth O vertex of the V octahedron is the terminal oxo ligand of a vanadyl group. Thus, the structure is described by a mixed paraframework of octahedra and tetrahedra {V2O2F[PO4](2)}infinityinfinityinfinity with disordered Na atoms in the interstices. The new phase is discussed as a member in the row of compounds structurally related to the mineral natisite and VOPO4.2H(2)O. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.