Cation–cation interaction in mixed-element Th(IV)/Np(V) chlorides, [Th(NpO2)6(H2O)8(OH)Cl9]·H2O and [Th(NpO2)6(H2O)9Cl9]Cl

Abstract

The compounds [Th(NpO₂)₆(H₂O)₈(OH)Cl₉]·H₂O (I) and [Th(NpO₂)₆(H₂O)₉Cl₉]Cl (II), in which mixed-element Th(IV)/Np(V) cation–cation interaction is observed, were isolated in the form of single crystals and studied by X-ray diffraction. The NpO₂⁺···NpO₂⁺ cation–cation bonds link the dioxocations into six-unit rings, and the NpO₂⁺···Th⁴⁺ bonds link these rings into a three-dimensional network. The compounds also contain a hydroxide ion incorporated in the Th⁴⁺ coordination surrounding or a chloride ion located in the interlayer space, depending on the synthesis conditions. The Np(V) pentagonal bipyramids in I and II are characterized by equal, within the uncertainty, bond lengths. The equatorial planes of the bipyramids are formed by three Cl^– anions, oxygen atom of the adjacent NpO₂⁺ cation, and oxygen atom of the water molecule. The Th⁴⁺ cations in I and II have the coordination surrounding in the form of tricapped trigonal prisms (CN 9) whose quadrangular lateral faces are formed by the oxygen atoms of the NpO₂⁺ cations and are capped by three water molecules. The Th⁴⁺ cations in I and II are arranged in the interlayer space, binding three cyclic moieties from each of the two adjacent layers.