Crystal Structures of K2MgCl4 and Cs2MgCl4
Supporting evidence for complex ion formation in MgCl2 alkali chloride melts was sought from a single crystal X-ray analysis of the title compounds. Crystals of K2MgCl4 are tetragonal, a = 4.94, c = 15.58 Å, Z = 2, space group I 4/mmm. The compound is isostructural with K2NiF4, and was determined with MoK α diffractometer data and refined by full-matrix least-squares to R = 0.046 for 180 reflections.Crystals of Cs2MgCl4 are orthorhombic, a = 9.777, b = 7.514, c = 13.234 Å,Z = 4, space group Pnma. The compound is isostructural with β-K2SO4, and was determined with MoKα diffractometer data and refined by full-matrix least-squares to R = 0.074 for 1084 reflections. The K2MgCl4 structure contains an infinite two-dimensional array of MgCl6 octahedra sharing edges. The Cs2MgCl4 structure contains discrete MgCl42− anions which likely continue to exist in the melt close to the melting point.