Redetermination of the cubic struvite analogue Cs[Mg(OH(2))(6)](AsO(4)).

In contrast to the previous refinement from photographic data [Ferrari et al. (1955 ▶). Gazz. Chim. Ital.84, 169-174], the present redetermination of the title compound, caesium hexa-aqua-magnesium arsenate(V), revealed the Cs atom to be on Wyckoff position 4d instead of Wyckoff position 4b of space group F3m. The structure can be derived from the halite structure. The centres of the complex [Mg(OH(2))(6)] octa-hedra and the AsO(4) tetra-hedra (both with 3m symmetry) are on the respective Na and Cl positions. The building units are connected to each other by O-H⋯O hydrogen bonds. The Cs(+) cations (3m symmetry) are located in the voids of this arrangement and exhibit a regular cubocta-hedral 12-coordination to the O atoms of the water mol-ecules. The O atom bonded to As has 2mm site symmetry (Wyckoff position 24f) and the water-mol-ecule O atom has m site symmetry (Wyckoff position 48h).