Synthesis and crystal-chemical features of two new uranyl chromates with the structures derived from [(UO2)(T6+O4)(H2O)n]0 (T = Cr6+, S6+, Se6+, n = 0–2)

Аннотация

Two new chromates of hexavalent uranium, [C₃H₁₀N][(UO₂)(CrO₄)(NO₃)] (1) and [C₂H₈N]₂[(UO₂)₂· (CrO₄)₂(Cr₂O₇)](H₂O)₂ (2), were prepared by a combination of hydrothermal synthesis and isothermal evaporation. Compounds 1 and 2 crystallize in the triclinic system, space group \(P\overline 1 \); a = 7.245(3), b = 7.329(3), c = 11.359(4) Å; α = 85.549(6)°, β = 82.547(6)°, γ = 80.174(6)° for 1; a = 7.2063(4), b = 11.5107(7), c = 16.0980(11) Å; α = 70.736(4)°, β = 80.246(4)°, γ = 71.759(4)° for 2. The structures were solved by the direct methods and refined to R₁ = 0.064 [for 1495 reflections with Fo > 4σ(Fo)] and 0.047 [for 4529 reflections with Fo > 4σ(Fo)] for 1 and 2, respectively. The crystal structure of 1 is based on [(UO₂)(CrO₄)(NO₃)]^– chains between which the isopropylamine molecules are arranged. In the structure of 2, the amine and H₂O molecules are localized between the [(UO₂)₂(CrO₄)₂(Cr₂O₇)]^2– layers. The uranyl chromate complexes described are derived from [(UO₂)(TO₄)(H₂O)_n]⁰ chains (T = Cr⁶⁺, S⁶⁺, Se6+, n = 0–2). A brief review of uranyl compounds with tetrahedral TO₄^2– anions (T = Cr⁶⁺, S⁶⁺, Se⁶⁺) and similar structural organization is given.