Abstract: | The synthesis and X-ray diffraction analysis of K2(H5O2)[UO2(C2O4)2(HSeO3)] single crystals have been performed. This compound crystallizes in the triclinic system with the unit-cell parameters a = 6.7665(4) ?, b = 8.8850(4) ?, c = 12.3147(7) ?, α = 94.73°, β = 90.16°, γ = 92.11°, sp. gr. P[`1]Pbar 1, Z = 2, and R = 0.019. The basic structural units are island [UO2(C2O4)2(HSeO3)]3− groups, which belong to the AB 201 M 1 crystallochemical group of uranyl complexes (A = UO22+, B 01 = C2O42−, and M 1 = HSeO3−). Uraniumcontaining complexes are linked through K+ and H5O2+ ions and via a system of hydrogen bonds with the participation of oxonium hydrogen atoms in this structure. |