A novel phosphomolybdate structure: crystal structure of [NH4]5[(MoO3)5(PO4)(HPO4)],3H2O

Abstract

The crystal structure of the title compound has been studied by X-ray diffraction methods from counter data. Crystals are orthorhombic, space group P2₁2₁2₁, with parameters a= 14·699(2), b= 9·725(1), c= 18·201(2)Å. The structure was solved by direct methods and refined by full-matrix least squares to R 0·029 for 4·808 observed reflections. The anion consists of a ring of five distorted MoO₆ octahedra. Of the five links in the ring, four involve shared edges, and the fifth a shared apex of MoO₆ octahedra. The crown thus formed is capped on one face by PO₄^3– and on the other by HPO₄^2–. The three phosphate oxygen atoms shared by the MoO₆ octahedra are of two types : one type (two on each phosphate) consists of oxygen atoms bridging two molybdenum atoms, and the other, the third phosphate oxygen, is shared by only one molybdenum atom. The phosphomolybdate anions are held together by a network of strong hydrogen bonds.