Hydrothermal Descriptive Chemistry and Single Crystal Structure Determination of Cesium and Rubidium Thorium Fluorides

Two new cesium thorium fluorides and three new rubidium thorium fluorides have been synthesized hydrothermally and structurally characterized. The structures of two polymorphs of CsTh<sub>3</sub>F<sub>13</sub> are described in space group <i>P</i>6/<i>mmm</i> with <i>a</i> = 8.2608(14) and <i>c</i> = 8.6519(17) and space group <i>Pmc</i>2<sub>1</sub> with <i>a</i> = 8.1830(16), <i>b</i> = 7.5780(15), and <i>c</i> = 8.6244(17). The analogous orthorhombic compound RbTh<sub>3</sub>F<sub>13</sub>, with <i>a</i> = 8.1805(16), <i>b</i> = 7.4378(15), and <i>c</i> = 8.6594(17) in space group <i>Pmc</i>2<sub>1</sub>, is also reported. Two other rubidium thorium fluorides are also described: RbTh<sub>2</sub>F<sub>9</sub> crystallizes in the space group <i>Pnma</i> where <i>a</i> = 8.9101(18), <i>b</i> = 11.829(2), and <i>c</i> = 7.4048(15), and Rb<sub>7</sub>Th<sub>6</sub>F<sub>31</sub> crystallizes in the space group <i>R</i>3̅ where <i>a</i> = 15.609(2) and <i>c</i> = 10.823(2). Comparison of these materials was made on the basis of their structures and synthesis conditions. The formation of these species in hydrothermal fluids appears to be dependent upon the concentration of the alkali fluoride mineralizer solution and, thus, the ratio of alkali ions to thorium in the system.