Synthesis and structure of crystalline complexes of Np(V) with isophthalic acid. Cation-cation interaction in the compounds [(NpO2)2(C6H4(COO)2)(H2O)]·H2O and M[(NpO2)(C6H4(COO)2)]·2.5H2O, M = [H3O], [NH4], and [C(NH2)3

Abstract

New Np(V) isophthalate complexes of the compositions [(NpO2)2(C6H4(COO)2)(H2O)]·H2O (I) and M[(NpO2)(C6H4(COO)2)]·nH2O, where M = [H3O] (IIa), [NH4] (IIb), and [C(NH2)3] (IIc), were synthesized and studied by single crystal X-ray diffraction. Cation-cation interaction was revealed in their structure. In the structure of I, each of three nonequivalent NpO2 groups is a bidentate ligand and simultaneously coordinates two adjacent neptunyl(V) ions to form “square” cationic networks. The cationic networks in the crystal are linked by bridging [C6H4(COO)2]2− anions exhibiting the coordination capacity equal to 5. Three independent Np atoms are characterized by different shapes of the coordination polyhedron (CP): hexagonal, pentagonal, and tetragonal bipyramids. Tetrameric cationic complexes in which each NpO2 group is a monodentate ligand and a coordination center for the adjacent group are formed in the structure of II. The cationic complexes are linked by the bridging [C6H4(COO)2]2− anions whose coordination capacity is 4; the CPs of the Np atoms are pentagonal bipyramids. In the structure of II, replacement of relatively small outer-sphere hydroxonium and ammonium cations by guanidinium cation does not alter the overall structural motif of the crystal.