Crystal Structures of K2MgC14 and CszMgC14

CYRIL S. GIBBONS, VINCENT C. REINSBOROUGH, and W. ALEXANDER WHITLA. Can. J. Chem. 53, 114(1975). Supportingevidence for complex ion formation in MgC12 alkali chloride melts was sought from a single crystal X-ray analysis of the title compounds. Crystals of K2MgC14 are tetragonal, a = 4.94, c = 15.58 A,z = 2, space groupI 4lmmm. The compound is isostructural with K2NiF4, and was determined with MoKa diffractometer data and refined by full-matrix least-squares to R = 0.046 for 180 reflections. Crystals ofCszMgC14are orthorhombic, a = 9.777, b = 7.514, c = 13.234 A , z =4, spacegroup Pnma. The compound is isostructural with P-KzS04, and was determined with MoKa diffractometer data and refined by full-matrix least-squares to R = 0.074 for 1084 reflections. The KzMgC14 structure contains an infinite two-dimensional array of MgC16 octahedra sharingedges. The CszMgCla structure contains discrete MgC142anions which likely continue to exist in the melt close to the melting point.