A new series of oxyhalides based on (Nb6Cl11iOi)Cl6a units with oxygen in statistical occupancy: M2renb6Cl17O. The crystal structure of Cs2LuNb6Cl17O

The new series of oxyhalides M2RENb6Cl17O (M = monovalent cation, RE = rare earths) with 16 valency electrons per Nb6 cluster is isotypic with MRENb6Cl18 (trigonal, space group R 3̄). The crystal structure of Cs2LuNb6Cl17O, a = 9.3863(6) Å, c = 25.664(5) Å, Z = 3, refined from single crystal X-ray diffraction data, indicates that it is based on [(Nb6Cl11iOi)Cl6a]5− units in which one oxygen is in statistical occupancy on the twelve inner positions. The observed interatomic distances are correlated with the VEC, the charge of the unit, and the matrix effect owing to both the oxygen and chlorine ligands surrounding the Nb6 cluster.