The compounds KAs4O6 X (X=Cl, Br, I) and NH4As4O6 X (X=Br, I): Hydrothermal syntheses and structure determinations

Abstract

The crystal structures of five isotypic hexagonal compounds with general formulaMAs4O6X [M=K, NH4;X=Cl, Br, I; space group: P622;Z=1] were determined from ∼ 370 single crystal X-ray data and refined toR values <0.05. The structure type is characterized by neutral charged\(\mathop \infty \limits^2\) [As2O3] sheets arranged parallel (00.1). The As atoms of neighbouring two sheets point to each other and the sheets are combined by interlayeredM andX atoms, respectively. TheM atoms are coordinated to twelve oxygen atoms, theX atoms are coordinated to twelve arsenic atoms. In both cases the coordination polyhedron is a hexagonal prism. The compounds were synthesized by thermal treatments of cubic As2O3 and potassium or ammonium haloids in a saturated aqueous solution of potassium acetate resp. ammonia [500 K, saturation vapour pressure].