The title compound, (NH4)(5)Na-7[Mo5P2O23](2)center dot 21H(2)O, was prepared under atmospheric conditions in aqueous solution at room temperature. The structure contains the [Mo5P2O23](6-) heteropolyoxometallate anion, which has been previously reported a number of times with a variety of differing countercations. Each anion is built up of five MoO6 octahedra sharing an edge and forming a ring which is closed by common corners of the terminal octahedra. The rings are closed on both sides by two asymmetric PO4 tetrahedra, sharing three corners with three MoO6 octahedra. The anions are chiral and the two independent anions in the asymmetric unit were arbitarily chosen with the same chirality, but the centrosymmetric crystal contains both enantiomers. The structure can alternatively be described as a succession of layers parallel to (101), formed by the [Mo5P2O23](6-) anions and linked by sodium chains. Water molecules and ammonium ions fill the remaining space and ensure the cohesion through extensive N-H center dot center dot center dot O and O-H center dot center dot center dot O hydrogen bonding.
2010. Vol. E66, 20-21 p.