Synthesis and structural characterization of a hydrated sodium–caesium tetracosatungstate(VI), Na₅Cs₁₉[W₂₄O₈₄]·21H₂O

Crystal formation of pentasodium nonadecacesium tetracosatungstate(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 3̄ 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 3 i ) arising from the conversion mediated by Cs + counter-ions.