Redetermination of the cubic struvite analogue Cs[Mg(OH2)6](AsO4)

Matthias Weil

doi:10.1107/s1600536808043171

Abstract

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 hexaaquamagnesium arsenate(V), revealed the Cs atom to be on Wyckoff position 4d instead of Wyckoff position 4b of space group F 3m. The structure can be derived from the halite structure. The centres of the complex [Mg(OH2)6] octahedra and the AsO4 tetrahedra (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 cuboctahedral 12-coordination to the O atoms of the water molecules. The O atom bonded to As has 2mm site symmetry (Wyckoff position 24f) and the water-molecule O atom has m site symmetry (Wyckoff position 48h).

Highlights

Ital. 84, 169–174], the present redetermination of the title compound, caesium hexaaquamagnesium arsenate(V), revealed the Cs atom to be on Wyckoff position 4d instead of Wyckoff position 4b of space group F43m
Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software; data reduction: HELENA implemented in PLATON (Spek, 2003); method used to solve structure: coordinates taken from an isotypic compound; program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ATOMS (Dowty, 2004); software used to prepare material for publication: SHELXL97
Symmetry codes: (i) −y+1, z+1, −x+1; (ii) z+1, −x+1, −y+1; (iii) −x+1, −y+1, z+1; (iv) −y+1/2, z+1/2, −x+1; (v) z+1/2, −x+1, −y+1/2; (vi) −x+1, −y+1/2, z+1/2; (vii) y+1/2, z+1, x+1/2; (viii) y+1, z+1/2, x+1/2; (ix) x+1/2, y+1/2, z+1; (x) z+1, x+1/2, y+1/2; (xi) z+1/2, x+1/2, y+1; (xii) x+1/2, y+1, z+1/2; (xiii)

Summary

Friedel pairs

In contrast to the previous refinement from photographic data [Ferrari et al (1955). The Cs+ cations (43m symmetry) are located in the voids of this arrangement and exhibit a regular cuboctahedral 12coordination to the O atoms of the water molecules. The O atom bonded to As has 2mm site symmetry 24f) and the water-molecule O atom has m site symmetry (Wyckoff position 48h). Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software; data reduction: HELENA implemented in PLATON (Spek, 2003); method used to solve structure: coordinates taken from an isotypic compound; program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ATOMS (Dowty, 2004); software used to prepare material for publication: SHELXL97

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