Synthesis and X‑ray Crystallography of [Mg(H2O)6][AnO2(C2H5COO)3]2 (An = U, Np, or Pu)

Synthesis and X-ray crystallography of single crystals of [Mg­(H2O)6]­[AnO2(C2H5COO)3]2, where An = U (I), Np (II), or Pu (III), are reported. Compounds I–III are isostructural and crystallize in the trigonal crystal system. The structures of I–III are built of hydrated magnesium cations [Mg­(H2O)6]2+ and mononuclear [AnO2(C2H5COO)3]− complexes, which belong to the AB013 crystallochemical group of uranyl complexes (A = AnO22+, B01 = C2H5COO–). Peculiarities of intermolecular interactions in the structures of [Mg­(H2O)6]­[UO2(L)3]2 complexes depending on the carboxylate ion L (acetate, propionate, or n-butyrate) are investigated using the method of molecular Voronoi–Dirichlet polyhedra. Actinide contraction in the series of U­(VI)–Np­(VI)–Pu­(VI) in compounds I–III is reflected in a decrease in the mean AnO bond lengths and in the volume and sphericity degree of Voronoi–Dirichlet polyhedra of An atoms.