STRUCTURE OF K3NA4H2[TBW10O36].20H2O

Tripotassium tetrasodium dihydrogen decatungstoterbate icosahydrate, K3Na4H2[TbW10O36].-20H2O M(r) = 3209, monoclinic, P2(1)/n, a = 29.772 (8), b = 16.164 (2), c = 11.443 (1) angstrom, beta = 96.01 (2)-degrees, V = 5476 (2) angstrom3, Z = 4, D(x) = 3.81 g cm-3, lambda(Mo K-alpha) = 0.71069 angstrom, mu = 230 cm-1, F(000) = 5584, T = 298 K, R = 0.053 for 8398 unique reflections. The D4d [TbW10O36]9- anion consists of two [W5O18]6- groups chelating to the central Tb3+ ion. The Tb3+ cation exhibits a tetragonal antiprismatic coordination with Tb-O distances of 2.40-2.44 angstrom. The average Tb-W distance is 3.83 angstrom. Two K+ cations play a prominent role in linking the two highly negatively charged [W5O18]6- units of the polyanion. While the three K+ cations have direct contacts to the polyanion O atoms, forming bridges to the neighboring polyanions, only one O atom of the polyanion is observed in the coordination spheres of the four Na+ cations.