Specific Features of the Crystal Chemistry of Layered Uranyl Compounds with the Ratio UO2: TO4 = 5 : 8 (T = S6+, Cr6+, Se6+, Mo6+)

Abstract

Two new U(VI) compounds templated with organic molecules, [(CH₆N)₃(H₂O)][(CH₆N)₂(C₃H₁₀N)· (H₂O)][(UO₂)₅(CrO₄)₈(H₂O)] (1) and [(C₆H₁₀N₃O₃)(H₅O₂)₂(H₂O)][(H₅O₂)₃(H₂O)][(UO₂)₅(SO₄)₈(H₂O)] (2), were prepared by combination of hydrothermal synthesis and isothermal evaporation methods. Compounds 1 and 2 crystallize in the monoclinic system, space group P2₁/n, a = 21.921(5), b = 11.016(2), c = 22.021(5) Å, β = 90.571(5)° for 1 and P₂/c, a = 18.1693(17), b = 10.0732(10), c = 30.098(3) Å, β = 103.427(2)° for 2. The reflections from the single crystals were collected at 100 K. The structures were solved by the direct methods and refined to R₁ = 0.053 and 0.070 for 1 and 2, respectively. The crystal structures of 1 and 2 are based on [(UO₂)₅(TO₄)₈(H₂O)]^6– modular layers (T = S⁶⁺, Cr⁶⁺) between which protonated organic molecules, water molecules, and hydroxonium ions are located. Specific features of the crystal chemistry of U(VI) compounds with tetrahedral oxoanions with the ratio UO₂: TO₄ = 5: 8 (T = S⁶⁺, Cr⁶⁺, Se⁶⁺, Mo⁶⁺) are considered.