Abstract

A new Nb₆ oxychloride, PbLu₃Nb₆Cl₁₅O₆, has been synthesized from stoichiometric amounts of PbO, Lu₂O₃, Nb₂O₅, NbCl₅ and Nb, heated at 680 °C. The crystal structure has been determined by single crystal X-ray diffraction (cubic, Pn, a = 13.8327(4) Å, V = 2646.8(1) Å³, Z = 4). The structure consists of a f.c.c. stacking of discrete edge-capped Nb₆Clⁱ₆Oⁱ₆Cl^a₆ units in which six oxygen and six chlorine atoms are ordered on the twelve inner positions, while the six apical ones are occupied by six chlorines. Additional chlorines, which do not belong to the former units, are bonded to the lutetium atoms to form Lu₂Cl₂ entities that occupy 3/4 of the tetrahedral cavities of the stacking units, while the lead ions are randomly distributed in the 1/4 remaining tetrahedral and in the octahedral cavities. The Nb₆Cl₁₂O₆ units are connected to each other by both the Lu₂Cl₂ entities and the lead ions to form a three-dimensional framework. This compound exhibits 14 valence electrons per cluster.