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 CsTh3F13 are described in space group P6/mmm with a = 8.2608(14) and c = 8.6519(17) and space group Pmc21 with a = 8.1830(16), b = 7.5780(15), and c = 8.6244(17). The analogous orthorhombic compound RbTh3F13, with a = 8.1805(16), b = 7.4378(15), and c = 8.6594(17) in space group Pmc21, is also reported. Two other rubidium thorium fluorides are also described: RbTh2F9 crystallizes in the space group Pnma where a = 8.9101(18), b = 11.829(2), and c = 7.4048(15), and Rb7Th6F31 crystallizes in the space group R3̅ where a = 15.609(2) and c = 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.