Crystal structure of Cs(2)GdNb(6)Cl(15)O(3) in the structural evolution of niobium oxychlorides with octa­hedral Nb(6)-cluster units

Cs(2)GdNb(6)Cl(15)O(3), dicaesium gadolinium hexa­niobium penta­deca­chloride trioxide, was synthesized by solid-state reactions starting from a stoichiometric mixture of CsCl, Gd(2)O(3), Nb, NbCl(5), and Nb(2)O(5). The crystal structure is based on octa­hedral Nb(6) cluster units (point group symmetry 3.2) with composition [(Nb(6)Cl( i ) (9)O( i ) (3))Cl( a ) (6)](5–) where i and a denote inner and outer ligands. Cs(2)GdNb(6)Cl(15)O(3) exhibits 14 valence electrons per cluster unit. The cluster units are linked to each other by Cs(I) and Gd(III) atoms, whereby Cs(I) (site symmetry 3..) is 12-coordinated by six Cl( i ) and six Cl( a ) ligands belonging to six neighboring cluster units and Gd(III) (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]. Cs(2)GdNb(6)Cl(15)O(3) is isotypic with Cs(2)UNb(6)Cl(15)O(3).