Abstract
Reaction of uranium salts with several lacunary polyoxotungstate anions yields four new heteropolyanion assemblies in which the uranium atoms occupy pentagonal bipyramidal coordination polyhedra. Treatment of A,α-[SiW9O34]10− with UO2(NO3)2 leads to Na14[Na2(UO2)2(SiW9O34)2]⋅38H2O (1, Monoclinic, P21/c, a=16.5719(8) Å, b=14.1689(7) Å, c=21.2528(10) Å, β=111.6670(10)°, V=4786.6(4) Å3, Z=2) which proves to be isostructural with the analogous derivative of [PW9O34]9− reported previously. Solutions of 1 exhibit the 5-line W-NMR spectrum expected for the structure of C i point symmetry. The salt (NH4)17[(UO2)3(H2O)4As3W26O94]⋅16H2O (2, Orthorhombic, Pnma, a=40.1747(2) Å, b=18.25840(10) Å, c=18.0817(2) Å, V=13263.4(2) Å3, Z=4) was isolated in 64% yield from a reaction of UO2(NO3)2 with B,α-[AsW9O33]9−. The structure of the anion in 2 has C s symmetry and contains one α-AsW9O33 and two novel β-AsW8O30 units linked by the UO2+ 2 groups; an additional WO6 links the two AsW8 fragments. Spectrophotometric titration of UCl4 with the sodium salt of [As4W40O140]28− indicated the formation of a 4:1 U:As4W40 complex. During attempts to isolate a crystalline product from this reaction the uranium became oxidized and a guanidinium salt of [Na(UO2)3(OH)(H2O)6As4W40O140(WO)]18− (3, Orthorhombic, Fdd2, a=54.848(3) Å, b=80.809(4) Å, c=20.2874(2) Å, V=89919(7), Z=16) was isolated. The partially disordered structure of 3 shows the S2 and adjacent sites of the lacunary As4W40 anion to be occupied by three UO5 and one WO5 polyhedra. A tetrameric assembly of γ-SiW10 units linked by UO2+ 2 groups occurs in [{M(OH2)}4(UO2)4(OH)2(SiW10O36)4]22− (lithium salt, M=Na, 4a, tetragonal, P42/nmc, a=b=26.5285(2) Å, c=15.0463(2) Å, V=10589.0(2) Å3, Z=2; sodium-potassium salt, M=K, 4b, orthorhombic, Fddd, a=24.180(5) Å, b=31.696(6) Å, c=58.012(12) Å, V=44460(15) Å3, Z=8). Tungsten-183 NMR spectra show the slow transformation of the expected 5-line (1:1:1:1:1) spectrum of 4a to a new species giving a 6-line spectrum (2:2:2:1:2:1). The latter complex has not been successfully isolated.
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Kim, KC., Gaunt, A. & Pope, M.T. New Heteropolytungstates Incorporating Dioxouranium(VI). Derivatives of α-[SiW9O34]10−, α-[AsW9O33]9−, γ-[SiW10O36]8−, and [As4W40O140]28− . Journal of Cluster Science 13, 423–436 (2002). https://doi.org/10.1023/A:1020507201056
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DOI: https://doi.org/10.1023/A:1020507201056