A Novel Layered Niobium Oxychloride Compound Based on Nb₂ Pairs and Nb₆ Octahedral Clusters: Synthesis and Crystal and Electronic Structures of Nb₁₀Cl₁₆O₇

The synthesis, single crystal structure determination, and electronic structure of Nb10Cl16O7, the first Nb6 oxychloride stabilized without countercation, are reported in this work. The crystal structure is very original since it consists of layers built up from both Nb6 octahedral clusters and Nb2 pairs. The Nb6Oi6Cli6Cla6 and Nb2(μ2-Cl)2Cl4O4 units form [Nb6Cli6Oi4Oi-i2/2Cla-a4/2Cla2]∞ infinite chains and [{Nb2(μ2-Cl)2O2/2Cl4/2O2}2]∞ 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 Nb6 cluster oxyhalides, as well as NbOCl2 and NbCl4 containing Nb2 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 Nb6Cli6Oi6Cla6 unit whereas the 6 others (i.e., 1.5 per Nb atom) participate in the bonding in the distorted [{Nb2(μ2-Cl)2O2/2Cl4/2O2}2]∞ double chains.