Redetermination of the hexa­gonal struvite analogue Cs[Mg(OH2)6](PO4)

The structure of the hexa-gonal modification of caesium hexa-aqua-magnesium phosphate has been redetermined from single-crystal X-ray data. The previous refinement from photographic data [Ferrari, Calvaca & Nardelli (1955 ▶). Gazz. Chim. Ital.85, 1232-1238] was basically confirmed, but with all H atoms located and with all non H-atoms refined with anisotropic displacement parameters. The structure can be derived from the NiAs structure type: the PO(4) tetra-hedra (3m. symmetry) are on the Ni positions and the complex [Mg(OH(2))(6)] octa-hedra (3m. symmetry) are on the As positions. The building units are connected to each other by hydrogen bonds. The Cs(+) cations (3m. symmetry) are located in the voids of this arrangement and exhibit a distorted cubocta-hedral 12-coordination by the O atoms of the water mol-ecules.