The Complex Symmetry Relationships of Methylammonium Hexafluoroantimonates [(CH3)XNH4-X]SbF6 (X=1-4) with CsCl-Type High-Temperature Structures

The methylammonium hexafluoroantimonates [(CH3)(X)NH4-X]SbF6 (X = 1-4)were synthesized from the corresponding antimonates by heating in 40 wt % aqueous HF and characterized by single-crystal diffraction. At elevated temperatures, the compounds crystallize in aristotype structures of the CsCl type with practically unrestricted rotational freedom of the ions. Upon cooling, ordered hettotype structures are formed with up to a 144-fold symmetry descent with respect to the parent structure. A detailed account of the complex structural relationships and of the twinning is given.

Automated summary

Methylammonium hexafluorantimonates [(CH3)(X)NH4-X]SbF6 (X = 1-4) were synthesized via heating in 40 wt% aqueous HF and characterized using single-crystal diffraction. The compounds exhibit aristotype structures of the CsCl type with unrestricted rotational freedom of the ions at elevated temperatures. Cooling leads to the formation of ordered hettotype structures with a symmetry descent of up to 144-fold compared to the parent structure. Detailed accounts of the complex structural relationships and twinning are provided.