Syntesis and Crystal Structure of Cs2Nb6Br5F12: A Nb6 Cluster Compound with a One-Dimensional Nb6Bri5Fi7Fa6 Unit Connection

The synthesis and the crystal structure of Cs2Nb6Br5F12 containing octahedral niobium clusters are presented in this work. This bromofluoride is based on a Nb6Li12Fa6 (L=Br and F) unit and crystallizes in the orthorhombic system (space group, Cccm; Z= 4; a=9.2446(2) ?, b=13.6256(3) ?, and c=17.1665(4) ?; R=0.0241). Fluorine and bromine are randomly distributed on the inner ligand positions, Li, that edge-bridge the Nb6 cluster whereas fluorine fully occupies the apical positions (La). The units are linked to each other by apical ligands leading to an original one-dimensional unit connection. The cesium atoms are statistically distributed on several sites that describe parallel channels along the [1 0 0] direction. The influence of fluorine ligands upon the stabilization of this structure type as well as the structural relationships with Ba2Zr6Cl17(B), Nb6F15, and NaMo6Cl13 will be evidenced and discussed.