High temperature redox reactions with uranium: Synthesis and characterization of Cs(UO2)Cl(SeO3), Rb2(UO2)3O2(SeO3)2, and RbNa5U2(SO4)7

Cs(UO2)Cl(SeO3) (1), Rb2(UO2)3O2(SeO3)3 (2), and RbNa5U2(SO4)7 (3) single crystals were synthesized using CsCl, RbCl, and a CuCl/NaCl eutectic mixture as fluxes, respectively. Their lattice parameters and space groups are as follows: P21/n (a=6.548(1) A, b=11.052(2) A, c=10.666(2) A and β=93.897(3)°), P 1 ¯ (a=7.051(2) A, b=7.198(2) A, c=8.314(2) A, α=107.897(3)°, β=102.687(3)° and γ=100.564(3)°) and C2/c (a=17.862(4) A, b=6.931(1) A, c=20.133(4) A and β=109.737(6)°. The small anionic building units found in these compounds are SeO32− and SO42− tetrahedra, oxide, and chloride. The crystal structure of the first compound is composed of [(UO2)2Cl2(SeO3)2]2− chains separated by Cs+ cations. The structure of (2) is constructed from [(UO2)3O11]16− chains further connected through selenite units into layers stacked perpendicularly to the [0 1 0] direction, with Rb+ cations intercalating between them. The structure of compound (3) is made of uranyl sulfate layers formed by edge and vertex connections between dimeric [U2O16] and [SO4] polyhedra. These layers contain unusual sulfate–metal connectivity as well as large voids.