Fehlordnung von Kationen und Kristallwasser bei kubischen Alkalitetrabromo- und -iodothallaten(III)/Disorder of Cations and Water Molecules in Cubic Tetrabromo- and -iodothallates

Abstract

<jats:title>Abstract</jats:title><jats:p> Tetrabromo- and -iodothallates(III) of the alkali cations crystallise from aqueous solutions as cubic hydrates MTlX<jats:sub>4</jats:sub>·nH<jats:sub>2</jats:sub>O (M = Li, Na, K, Rb, Cs, NH<jats:sub>4</jats:sub>; X = Br, I; n = 1-2). The tetraiodothallates retain their cubic structure on dehydratisation, while the tetrabromothallates undergo structural changes. The X-ray structure analyses of RbTlBr<jats:sub>4</jats:sub> · H<jats:sub>2</jats:sub>O, NH<jats:sub>4</jats:sub>TlBr<jats:sub>4</jats:sub> · 2H<jats:sub>2</jats:sub>O and KTlBr<jats:sub>4</jats:sub> · 2H<jats:sub>2</jats:sub>O (-50 °C) showed that these compounds consist of a three-dimensional framework of TlBr<jats:sub>4</jats:sub> tetrahedra and MBr<jats:sub>12</jats:sub> ikosahedra which reminds of zeolites. In cavities of this framework 2/3 of the alkali cations and the crystal water molecules are accommodated in a disordered manner.</jats:p>