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CTURE OF ORGANIC COMPOUNDS

Crystal Structure of PbUO2(CH3COO)4(H2O)3 L. B. Serezhkinaa, A. V. Vologzhaninab, V. V. Klepova, and V. N. Serezhkina a

Samara State University, Samara, 443011 Russia Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, 119991 Russia email: [email protected]

b

Received May 19, 2010

Abstract—Single crystals of PbUO2(CH3COO)4(H2O)3 have been investigated by Xray diffraction (R = 0.029 for 3175 reflections). The structure of this compound is formed by [Pb(CH3COO)(H2O)3]+ chains, which are oriented along the [100] axis and limited by onecore complexes [UO2(CH3COO)3]–. The coor dination numbers of the Pb(II) and U(VI) atoms are 8, and the coordination polyhedron of uranium is a hex agonal bipyramid whose vertices contain oxygen atoms of three bidentate cyclic acetate groups and the uranyl group. Taking into account the different crystallographic roles of acetate ions, the crystalchemical formula 1 2+ of [PbUO2(CH3COO)4(H2O)3] chains can be written as AA'B21B11(B01)2 M 3 , where A = Pb; A' = UO 2 ; M1 = H2O; and B21, B11 , and B01 are CH3COO– groups. DOI: 10.1134/S1063774510061100

In all structurally studied uranyl acetates, the 2+ CH3COO–: UO 2 ratio is 3 : 1, which is consistent with the presence of [UO2(CH3COO)3]– complexes in the structure. There are data in the literature on the synthesis of uranyl acetate complexes and divalent cat ions with the general composition MUO2(CH3COO)4 · nH2O (M = Pb, Be, or Cd) with four acetate groups per uranyl group [1]; however, there are no data on the crystal structure of these compounds. The purpose of this study was to analyze the structure of PbUO2(CH3COO)4 · 3H2O (I), which we obtained according to [2] by the slow evaporation of an aqueous solution containing equimolar amounts of uranyl and lead acetates in the presence of acetic acid at room temperature.

There are four crystallographically different acetate ions in structure I: three of them (containing C1, C3, and C5 atoms, respectively) are involved in a bidentate cyclic bond with the uranyl ion to form the [UO2(CH3COO)3]– complex, and the fourth ion (with a C7 atom) is coordinated only by lead atoms. With 2+

allowance for the oxygen atoms of the UO 2 cation, the coordination polyhedron of the uranium atom is in the shape of a hexagonal bipyramid, which is charac 2+

teristic of uranyl triacetate complexes. The UO 2 cat

The parameters of the Xray experiment and the final reliability factors are listed in Table 1. The struc ture was resolved by the direct method; all nonhydro gen atoms were located from the difference electron density syntheses and refined in the anisotropic approximation. The coordinates of hydrogen atoms were found geometrically and refined in the isotropic approximation within the rigidbody model with Uiso(H) = 1.5Ueq(Xi), where Ueq(X) are the equivalent thermal parameters of the atoms to which the hydro gen atom is bonded. The main geometric parameters are listed in Table 2. The atomic coordinates and ther mal parameters