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

Abstract

The crystal structure of Mg(BrO 3 ) 2 ·6H 2 O 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(BrO 3 ) 2 ·6H 2 O(M = Co, Ni, Cu, Zn) and Ni(ClO 3 ) 2 ·6H 2 O. The Mg(BrO 3 ) 2 ·6H 2 O structure is related to fluorite, with Mg(H 2 O) 6 2+ replacing Ca 2+ and BrO 3 - 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. r OH 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 C 3v symmetry.