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Acta Cryst. (2013). E69, i48-i49  [ doi:10.1107/S1600536813018588 ]

Redetermination of MgCrO4·5H2O

M. Weil

Abstract: 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 [011]. Adjacent chains are linked through O-H...O hydrogen bonds (one of them bifurcated), involving both the coordinating and lattice water molecules, into a three-dimensional network.

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