X-RAY STRUCTURES OF - BIS(TETRAAQUA MAGNESIUM DIMETHYLARSINATE) TETRAAQUA MAGNESIUM TETRACHLORIDE MONOHYDRATE AND TETRAHYDRATE

The structures of (As2Mg3O16C4H36)4+.4Cl-.H2O [salt(1)] and (As2Mg3O16 C4H36)4+. 4Cl-.4H2O [salt(2)] have been determined. The magnesium atom s in the structures are coordinated by four water molecules and two ox ygen atoms of dimethylarsinate (cacodylate) group. All oxygen atoms, w ater molecules and chlorine anions in both structures form complicated networks of H-bonds. There are considerable differences in the struct ures of salt(1) and salt(2), which differ in composition only in conte nts of crystal water. The main difference is the conformation of the c hains: zigzag chain in salt(1) and linear one in salt(2).