A new hexa-gonal polymorph of magnesium perchlorate hexa-hydrate obtained from an acetamide medium.

A new magnesium perchlorate hexa-hydrate phase, Mg(ClO4)2·6H2O, was obtained from the mixed solvents of water and acetamide. The structure crystallizes in the hexa-gonal space group P63mc and is isostructural with previously reported M(ClO4)2·6H2O (M = Zn, Ni, Fe) phases. The Mg site is half occupied, indicating positional disorder of the metal cation. Prolonged crystallization leads to the formation of larger crystals consistent with an expanded unit cell, suggesting the formation of a disorder-related superstructure. The Mg, Cl and one of the O atoms have 3m. site symmetry.