Inorganic Chemistry, Vol.42, No.25, 8320-8327, 2003
A novel layered niobium oxychloride compound based on Nb-2 pairs and Nb-6 octahedral clusters: Synthesis and crystal and electronic structures of Nb10Cl16O7
The synthesis, single crystal structure determination, and electronic structure of Nb10Cl16O7, the first Nb-6 oxychloride stabilized without countercation, are reported in this work. The crystal structure is very original since it consists of layers built up from both Nb-6 octahedral clusters and Nb-2 pairs. The (Nb6O6Cl6Cl6Cl6a)-Cl-i-Cl-i and Nb-2(mu(2)-Cl)(2)Cl4O4 units form [(Nb6Cl6O4O2/2i-iCl4/2a-aCl2a)-O-i-O-i](infinity) infinite chains and [{Nb-2(mu(2)-Cl)(2)O2/2Cl4/2O2}(2)](infinity) double chains, respectively, that are interconnected by shared oxygen and chlorine ligands leading to layers. The cohesion of the three-dimensional structure (3D) is ensured by van der Waals contacts between layers that are randomly stacked along the [011] direction. Structural correlations between Nb10Cl16O7 and related Nb-6 cluster oxyhalides, as well as NbOCl2 and NbCl4 containing Nb-2 pairs, are discussed. DFT results show that among the 20 valence electrons involved in the metal-metal bonding states, 14 electrons belong to the octahedral (Nb6Cl6O6Cl6a)-O-i-Cl-i unit whereas the 6 others (i.e., 1.5 per Nb atom) participate in the bonding in the distorted [{Nb-2(mu(2)-Cl)(2)O2/2Cl4/2O2}(2)](infinity) double chains.