The Family of tetranuclear Nb4OI12-x Clusters (x = 0, 1, 2): From the molecular Nb4OI12 cluster to extended chains and layers

Abstract

Unconventional reduction reactions in the Nb-O-I system have produced a number of niobium oxyiodides containing the oxygen-centered [Nb4O] cluster. Crystalline Nb4OI12 and two modifications of Nb4OI11 were structurally characterized by means of single-crystal X-ray diffraction studies. The new compounds can be classified as members of the Nb4OI12-x family, together with the already known Nb4OI10. Nb4OI12 is represented by a molecular stucture, in which the two modifications of Nb4OI11 are forming structures with iodido-bridged strings, that can be assigned to represent one-dimensional structures. Measurements of b-Nb4OI11 single crystals reveal semiconducting behaviour, with an electrical conductivity in the order of 10-3 S/m at 300 K and an electrical band gap estimated with 0.4 eV. The presence of varying numbers of cluster electrons in the given compounds is discussed in the light of second-order Jahn-Teller distortion.