Received 2 July 2013
The CCD-data based redetermination of the crystal structure of the title compound, magnesium chromate(VI) pentahydrate, confirms in principle the previous study based on precession film data [Bertrand et al. (1971). C. R. Hebd. Seances Acad. Sci. Serie C, 272, 530-533.], but with all atoms refined with anisotropic displacement parameters and with all H atoms localized. This allowed an unambiguous assignment of the hydrogen-bonding pattern. MgCrO4·5H2O adopts the MgSO4·5H2O structure type. It contains two Mg2+ sites on special positions with site symmetry -1, one tetrahedral CrO4 group and five water molecules. Four of them coordinate to the Mg2+ cation, and one is an uncoordinating lattice water molecule. The octahedral environment of the Mg2+ cation is completed by two axial O atoms of CrO4 tetrahedra. This arrangement leads to the formation of chains parallel to . Adjacent chains are linked through O-HO hydrogen bonds (one of them bifurcated), involving both the coordinating and lattice water molecules, into a three-dimensional network.
For the original structure determination of the title compound, see: Bertrand et al. (1971). For hydrogen-bonding pattern in the structures of MXO4·5H2O compounds (M = Mg, Cu; X = S, Cr), see: Baur & Rolin (1972). For Cr-O bond length distributions in chromates(VI), see: Pressprich et al. (1988). For bond lengths and angles in the related structure of MgCrO4·11H2O, see: Fortes et al. (2013). For standardization of structure data, see: Gelato & Parthé (1987).
Data collection: APEX2 (Bruker, 2011); cell refinement: SAINT (Bruker, 2011); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ATOMS for Windows (Dowty, 2008); software used to prepare material for publication: publCIF (Westrip, 2010).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BR2229 ).
The X-ray centre of the Vienna University of Technology is acknowledged for financial support and for providing access to the single-crystal diffractometer.
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