Antiprismatische und dodekaedrische Oktaaquokationen von Calcium und Strontium in den Kristallstrukturen von Tetrahalogenocadmaten und -mercuraten / Antiprismatic and Dodecahedral Oktaaquo Cations of Calcium and Strontium in the Crystal Structures of Tetrahalogeno Cadmates and Mercurates

Abstract

<jats:title>Abstract</jats:title><jats:p> The tetrahalogenometallates CaHgBr<jats:sub>4</jats:sub>·8H<jats:sub>2</jats:sub>O, CaCdI<jats:sub>4</jats:sub>·8H<jats:sub>2</jats:sub>O and SrCdI<jats:sub>4</jats:sub>·8H<jats:sub>2</jats:sub>O which have been obtained by crystallization from aqueous solutions form different structures. The orthorhombic compounds CaHgBr<jats:sub>4</jats:sub>·8H<jats:sub>2</jats:sub>O (Cmca, a = 1720.1(6) pm, b = 1329.2(4) pm. c = 1369.5(7) pm, Z = 8, R =0.041) and SrCdI<jats:sub>4</jats:sub>·8H<jats:sub>2</jats:sub>O (Pnma, a = 1404.6(2) pm, b = 1841.1(5) pm. c = 1420.6(3) pm, Z = 8, R = 0.037) are built up from dodecahedral [A(H<jats:sub>2</jats:sub>O)<jats:sub>8</jats:sub> ] cations (A = Ca, Sr) and tetrahedral MX<jats:sub>4</jats:sub> anions (M = Hg, Cd) which are cubic closed packed in a CuAu type structure. The tetragonal structure of CaCdI<jats:sub>4</jats:sub>·8H<jats:sub>2</jats:sub>O (P4/nbm, a = 1268.14(13) pm, c = 536.96(35) pm. Z = 2, R = 0.034) contains antiprismatic [Ca(H<jats:sub>2</jats:sub>O)<jats:sub>8</jats:sub>]<jats:sup>2+</jats:sup> cations and tetrahedral Cdl<jats:sub>4</jats:sub> anions, which form together a tetragonal primitive rod package.</jats:p>