Synthesis and Structure of U(VI), Np(VI), and Pu(VI) 2-Fluorobenzoates

Abstract

The compounds NH₄[AnO₂(C₆H₄FCOO₃], where An = U (I), Np (II), or Pu (III), CgH₄COO⁻ is the 2-fluorobenzoate anion, were synthesized and studied by single crystal X-ray diffraction. Compounds I–III are isostructural and crystallize in the cubic system, space group P2₁3, Z = 4. The main structural units of I–III are mononuclear complexes [AnO₂(C₆H₄COO)₃]⁻ belonging to crystal-chemical group AB₃¹ (A = AnO₂²⁺, B⁰¹ = C₆H₄FCOO⁻). The actinide contraction in the structures of I–III is manifested in a regular decrease in the lengths of the An=0 bonds in the AnO₂²⁺ cations and in the volumes of the Voronoi-Dirichlet polyhedra (VDPs) of the An atoms in the series U-Np-Pu. The intermolecular interactions in crystal structures of I–III were analyzed by the method of molecular VDPs.