Abstract The sandwich-type [Na(UO2)2(H2O)4(BiW9O33)2]13− uranium (VI) has been synthesized by reacting the trivacant species of B-α-[BiW9O33]9− with and investigated by IR and UV–Vis spectroscopy, and elemental analysis. The X-ray single crystal analysis was carried out on Na13[Na(UO2)2(H2O)4(BiW9O33)2] · 33H2O (I) which crystallizes in the orthorhombic system, space group Pna21 with a = 33.8454(19) Å, b = 21.1484(12) Å, c = 13.2403(7) Å, α = 90°, β = 90°, γ = 90°, and Z = 4. The polyanion consists of two lacunary B-α-[BiW9O33]9− groups which sandwich two uranyl cations and one sodium cation. The uranium atoms adopt distorted pentagonal–bipyramidal coordination, achieved by two equatorial bonds to each BiW9O33 unit and one external water ligand. The coordination of each uranium atom is evident by the shift of νas(W–Ob–W) and νas(Bi–O) stretching vibrational bonds. Electronic supplementary material The online version of this article (doi:10.1007/s10876-008-0184-7) contains supplementary material, which is available to authorized users

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