Syntheses and structures determination of new polytungstoarsenates [Na2As2W18U2O72]12− and [MAs2W18U2O72]13− (M=NH4+andK+)

The isomerically pure title complexes are formed by the reaction of a neutralized (pH 7–7.5) solution of WO42- and HAsO42- with an UO22+ solution in a stoichiometric ratio. Sodium salt [Na2As2W18U2O72]12−, ammonium and potassium salts [MAs2W18U2O72]13−(M=NH4+,K+) are synthesized and characterized by elemental analysis, IR, Raman, As and W NMR spectroscopies and single crystal structure analysis. Single-line 75As, five-line 183W NMR and Raman spectra show that the sodium salt (1) contains an anion of Ci symmetry. The ammonium (2) and potassium (3) salts contain anions in which the two UO22+ and one ammonium or potassium cation are unsymmetrically sandwiched between two A-AsW9O349-groups. Each uranium atom adopts a pentagonal-bipyramidal coordination, achieved by three equatorial bonds to one AsW9O349- and two bonds to the other. The anions are converted to H6As2W18O62 in strongly acidic medium.

Graphical abstractNew sandwiched type tungstoarsenates of [Na2As2W18U2O72]12− and [MAs2W18U2O72]13− (M=NH4+,K+) have been synthesized by the self-assembly reaction of tungstate, arsenate and uranyl ions in a stoichiometric ratio and characterized by spectroscopy tools and single crystal structure analysis.Figure optionsDownload full-size imageDownload as PowerPoint slide