Crystal-Chemical Features of U(VI) Compounds with Inorganic Complexes Derived from [(UO2)(TO4)(H2O)n], T = S, Cr, Se: Synthesis and Crystal Structures of Two New Uranyl Sulfates

Abstract

Two new U(VI) sulfates, [CH₆N₃]₂(NO₃)₂[(UO₂)(SO₄)(H₂O)₂]·H₂O (1) and [C₅H₈N₂]₂[(UO₂)· (SO₄)₂] (2), were prepared by isothermal evaporation from aqueous solutions. Compound 1 crystallizes in the monoclinic system, space group P2₁/n, a = 12.3824(7), b = 7.0329(4), c = 21.5362(12) Å, β = 99.598(2)°, and compound 2, in the triclinic system, space group P1̅, a = 7.0126(9), b = 10.3352(13), c = 13.8027(19) Å, α = 68.187(5)°, β = 78.940(5)°, γ = 71.339(3)°. The crystal structure of the compounds was studied at 100 K. The structures were solved by direct methods and refined to R₁ = 0.059 and 0.032 for 1 and 2, respectively. The structure of 1 is based on electrically neutral [(UO₂)(SO₄)(H₂O)₂]⁰ chains between which protonated guanidine molecules, NO₃^– anions, and water molecules are located. In compound 2, protonated molecules of 4-aminopyridine bind [(UO₂)(SO₄)₂]^2– chains in a three-dimensional structure. Specific crystal-chemical features of chain U(VI) compounds with tetrahedral oxoanions, derived from [(UO₂)(TO₄)(H₂O)_n], T = S, Cr, Se, are considered.