Synthesis and crystal structure of new Np(VII) compounds, M[NpO4(OH)]·nH2O (M = Ca, Sr, Ba)

Abstract

Previously unknown Np(VII) compounds with alkaline earth metal cations of the composition M[NpO4OH]·nH2O (M = Ca, Sr, Ba) were prepared in the crystalline form and studied by single crystal X-ray diffraction analysis. The main structural motif in the compounds is formed by infinite anionic chains [NpO4· (OH)]n2n– in which the NpO4 groups are linked via common ОН groups. In the structures of Ca[NpO4(OH)]· 3H2O and Ca[NpO4(OH)]·4H2O, each Ca2+ cation links two anionic chains [NpO4(OH)]n2n–, so that electrically neutral layers are formed. In the structures of Sr[NpO4(OH)]·H2O and Ba[NpO4(OH)]·H2O, each of the Sr2+ and Ba2+ cations binds three anionic chains [NpO4(OH)]n2n–, so that a 3D framework is formed in the crystals. The outer-sphere cations influence the structure of the anionic chains.