A Supramolecular Star-like Tungstoarsenate(V) with Uranyl Cations: [(NH4)12(UO2(H2O))6(UO2(μ2-H2O))6(α-AsW9O34)6]18-

A supramolecular tungstoarsenate(V) containing UO22+ cations has been isolated by reaction of the ammonium salt of lacunary sandwich-type anion [As2W18(UO2)(2)O-68](14-) in aqueous solution of Ce-IV (pH 3.5). The product prepared as NH4+ salt, (NH4)(18)[(NH4)(12)(UO2(H2O))(6)(UO2(mu(2)-H2O)(6)(alpha-AsW9O34)(6)]center dot 74H(2)O (I), have been characterized by single crystal X-ray diffraction, elemental analysis, IR, and UV/vis spectroscopy. The anion consists on six lacunary alpha-AsW9O349- anions linked by twelve UO22+ cations which resembles a star (six-member). The single crystal structure of I reveals two types uranium atoms; six uranium atoms in the central of anion form two U3O3 trigonal bridging groups in which each uranium atom bounds to three oxygen atoms of one AsW9 and two bridging water ligands. The other uranium atoms form two equatorial bonds to one AsW9 and two equatorial bonds to two other AsW9 fragments. The UV/vis spectroscopy confirms the strong coordination of oxygen atoms of alpha-AsW9O349- anions to uranyl cations in the equatorial plane.