Crystal structure of Cs2GdNb6Cl15O3 in the structural evolution of niobium oxychlorides with octahedral Nb6-cluster units

Abstract

Cs2GdNb6Cl15O3, dicaesium gadolinium hexaniobium pentadecachloride trioxide, was synthesized by solid-state reactions starting from a stoichiometric mixture of CsCl, Gd2O3, Nb, NbCl5, and Nb2O5. The crystal structure is based on octahedral Nb6 cluster units (point group symmetry 3.2) with composition [(Nb6Cl i 9O i 3)Cl a 6]5– where i and a denote inner and outer ligands. Cs2GdNb6Cl15O3 exhibits 14 valence electrons per cluster unit. The cluster units are linked to each other by CsI and GdIII atoms, whereby CsI (site symmetry 3..) is 12-coordinated by six Cl i and six Cl a ligands belonging to six neighboring cluster units and GdIII (site symmetry 3.2) is 9-coordinated by three O i and six Cl i ligands belonging to three adjacent cluster units. The arrangement of cluster units corresponds to a stacking of …AA′A… layers along [001]. Cs2GdNb6Cl15O3 is isotypic with Cs2UNb6Cl15O3.