Abstract

The reaction of UO3 with SeO2 in the presence of SrCl2• 6H2O and Sr(OH)2• 8H2O in supercritical water at 425 °C for 3 d results in the formation of the new strontium uranyl selenites, Sr[(UO2)3(SeO3)2O2]•4H2O (1) and Sr[UO2(SeO3)2] (2). The single crystal X-ray structures of type 1 and type 2 were solved by direct methods and refined by full-matrix least-squares methods. Crystallographic data (193 K): (1), monoclinic, space group C2/m, a = 17.014(2), b = 7.0637(7), and c = 7.1084(7) Å, β = 100.544(2)°, Z = 2, R(F) = 0.0361 for 79 parameters with 1132 reflections with I > 2σ(I), wR2 = 0.0998 for all data; (2), triclinic, space group P1̅, a = 5.6722(4), b = 6.7627(5), and c = 11.2622(8) Å, α = 104.698(1)°, β = 93.708(1)°, γ = 109.489(1)°, Z = 2, R(F) = 0.0373 for 110 parameters with 1902 reflections with I > 2σ(I), wR2 = 0.0856 for all data. The structure of type 1 contains two-dimensional

\(^{2}_{{\infty}}{[}(UO_{2})_{3}(SeO_{3})_{2}O_{2}{]}^{2{-}}\)
sheets with the same topology as those found in guilleminite, Ba[(UO2)3(SeO3)2O2]•3H2O, and marthozite, Cu[(UO2)3(SeO3)2O2](H2O)8. Sr2+ cations and H2O groups occur between the layers. In contrast, the structure of type 2 contains one-dimensional
\(^{1}_{{\infty}}{[}UO_{2}(SeO_{3})_{2}{]}^{2{-}}\)
ribbons with Sr2+ cations residing between them. This compound is isostructural with its Ca2+-containing analog.

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