Structures of Binuclear Fluorooxalatouranylates Rb5[(UO2)2(C2O4)4F]⋅2H2O and Ba5[(UO2)2(C2O4)4F]2⋅22H2O

Abstract

The structures of novel crystals of Rb₅[(UO₂)₂(C₂O₄)₄F]·2H₂O (I) and Ba₅[(UO₂)₂(C₂O₄)₄F]₂⋅22H₂O (II) (CIF files CCDC nos. 2392480 (I) and 2392481 (II)) are studied by X‑ray diffraction (XRD). The uranyl-containing structural units are the binuclear complexes of the same composition [(UO₂)₂(C₂O₄)₄F]^5– but with different structures, which are described by the crystallochemical formulas \({{{\text{A}}}_{{\text{2}}}}{{{\text{T}}}^{{11}}}{\text{B}}_{{\text{3}}}^{{{\text{01}}}}{{{\text{M}}}^{{\text{1}}}}\) (I) and \({{{\text{A}}}_{{\text{2}}}}{\text{B}}_{{\text{4}}}^{{{\text{01}}}}{{{\text{M}}}^{{\text{2}}}}\) (II) (A = \({\text{UO}}_{{\text{2}}}^{{{\text{2 + }}}}\), T¹¹ or B⁰¹ = \({{{\text{C}}}_{{\text{2}}}}{\text{O}}_{{\text{4}}}^{{{\text{2}} - }}\), M¹ or M² = F^–). The complexes contain crystallographically nonequivalent U(VI) atoms, which are components of the uranyl ions and implement the pentagonal bipyramidal coordination. In compound I, the U(VI) atoms form coordination polyhedra UO₂FO₄ and UO₂O₅, and only UO₂FO₄ are formed in compound II. In both structures, the binuclear [(UO₂)₂(C₂O₄)₄F]^5– complexes are linked into a 3D framework due to coordination bonds R–O and R–F (R = Rb or Ba). The water molecules involved in the formation of a set of hydrogen bonds are localized in voids of the 3D framework. The IR spectroscopy results for compounds I and II are consistent with the XRD data.