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

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.