Synthesis and structural characterization of a hydrated sodium-caesium tetra-cosa-tungstate(VI), Na(5)Cs(19)[W(24)O(84)]·21H(2)O.

Crystal formation of penta-sodium nona-deca-cesium tetra-cosa-tungstate(VI) heneikosahydrate, Na(5)Cs(19)[W(24)O(84)]·21H(2)O, was successfully achieved by the conversion of [H(2)W(12)O(42)](10-) through the addition of excess Cs(+). The crystal structure comprising the toroidal isopolyoxidometalate is presented, as well as its Raman spectrum. Na(5)Cs(19)(H(2)O)(21)W(24)O(84) crystallizes in the rhombohedral space group R with an obverse centering. The title compound represents the addition of a new member to the isopolytungstate family with mixed alkali counter-ions and contains rarely observed five-coordinate tungsten(VI) atoms in the [W(24)O(84)](24-) anion (site symmetry C (3i) ) arising from the conversion mediated by Cs(+) counter-ions.