Die Kristallstruktur des Dinatrium-oktammonium-parawolframat-dodekahydrats, Na2(NH4)8[H2W12O42] · 12H2O*

Abstract

AbstractNa2(NH4)8[H2W12O42] · 12H2O crystallizes in space groupPbca,a= 15.78,b= 22.93,c= 14.13 Å,Z= 4,Dm= 4.12,Dx= 4.27 g · cm−3. The W atoms were located by a Patterson map, the lighter atoms (21 O, 1 Na, 4 NH4, 6 H2O) by aΔFmap. Using anisotropic temperature factors for W and isotropic ones for the other atoms, the structure was refined toR= 9.0% for 3069 reflections, 772 of which were unobserved (122 of these hadFo>Fmin). The anion [H2W12O42]10−is built up by four groups of three edge-sharing octahedra each. It exhibits 2/mpseudosymmetry (W–O = 1.96 Å). The Na atom is octahedrally surrounded by two O and 4 H2O (Na–O = 2.39 Å). The cations are bound to the polyanion at about the same sites as in ammonium paratungstate decahydrate and tetrahydrate.