Magnesium perchlorate anhydrate, Mg(ClO₄)₂, from laboratory X-ray powder data

The previously unknown crystal structure of magnesium perchlorate anhydrate, determined and refined from laboratory X-ray powder diffraction data, represents a new structure type. The title compound was obtained by heating magnesium perchlorate hexa-hydrate at 523 K for 2 h under vacuum and it crystallizes in the monoclinic space group P21/c. The asymmetric unit contains one Mg (site symmetry on special position 2a), one Cl and four O sites (on general positions 4e). The structure consists of a three-dimensional network resulting from the corner-sharing of MgO₆ octa-hedra and ClO ₄ tetra-hedra. Each MgO₆ octa-hedron share corners with six ClO₄ tetra-hedra. Each ClO₄ tetra-hedron shares corners with three MgO6 octa-hedra, with one O-atom corner dangling. The ClO₄ tetra-hedra are oriented in such a way that one-dimensional channels parallel to [100] are formed between the dangling O atoms.