Die Zwillings-Kristallstruktur von Mg(BrO3)2 · 6H2O / The Crystal Structure of Twinned Mg(BrO3)2 · 6H2O

Abstract

The crystal structure of Mg(BrO3)2·6H2O twinned crystals has been determined by X-ray single crystal diffraction (Pa3̅, a = 1039.56(9) pm). The structure is isomorphic to that of M(BrO3)2·6H2O(M = Co, Ni, Cu, Zn) and Ni(ClO3)2·6H2O. The Mg(BrO3)2·6H2O structure is related to fluorite, with Mg(H2O)6 2+ replacing Ca2+ and BrO3 - replacing F-. The water molecules are involved in nearly linear hydrogen bonds to adjacent bromate ions (νOD of matrix isolated HDO: 2458 and 2453 cm-1). The intramolecular O-H distances 96.84 and 96.90 pm have been derived from the wavenumbers of the respective OD stretches using a recently established vOD vs. rOH correlation curve. The infrared and Raman spectra show accidental degeneracy of the symmetric and the asymmetric BrO stretching modes, which is common for bromate ions with local C3v symmetry.