Synthesis and Structure of the [(UO₂)S₄]^6– Anion: A Cation-Stabilized Uranyl Sulfide

The new uranyl sulfide anion [(UO2)­S4]6– has been synthesized and characterized as a cation-stabilized anion in the compound Na2Ba2(UO2)­S4. This compound was synthesized at 873 K from the solid-state reaction of uranium, Na2O2, BaS, and sulfur. The coordination about the U6+ center in [(UO2)­S4]6– is square bipyramidal with the uranyl O atoms 180° apart and four equatorial S atoms. The Na+ and Ba2+ cations form interactions with the uranyl O atoms. Despite the inherent difficulties involved in the synthesis of complex uranium oxysulfides, it is demonstrated that under the right reaction conditions the UO22+ species can be produced in situ and result in totally new chalcogen derivatives.