Magnesium chloride tetrahydrate, MgCl2•4H2O

The title compound, MgCl2 center dot 4H(2)O, was crystallized at 403 K and its structure determined at 200 K. The structure is built up from MgCl2(H2O)(4) octahedra with a trans configuration. Each complex is situated on a crystallographic twofold axis, with the rotation axis aligned along one H2O-Mg-OH2 axis. They are connected by a complex network of O-H center dot center dot center dot Cl hydrogen bonds. The structure contains two-dimensional sections that are essentially identical to those in the reported tetrahydrates of CrCl2, FeCl2, FeBr2 and CoBr2, but they are stacked in a different manner in MgCl2 center dot 4H(2)O compared with the transition metal structures.