Niobium oxyiodide cluster compounds Li3Nb7O5I15 and Nb8O5I17(NbI5) with expanding cluster architectures and multicentre Nb–Nb bonding

Abstract

A series of niobium oxyiodide compounds has recently been identified using a non-conventional reduction method. The continuation of these studies of heterogeneous solid-state reactions in a closed system has led to the crystallization and structural analysis of two novel compounds Li₃Nb₇O₅I₁₅ and Nb₈O₅I₁₇(NbI₅). Both crystal structures are derived from the pentanuclear [Nb₅O₄] cluster core and are expanded through the incorporation of additional niobium atoms, forming new [Nb₇O₅] and [Nb₈O₅] cluster cores. Furthermore, it is shown that oxyiodide clusters containing between four and eight niobium atoms can form from the same mixture of reactants by simply adjusting the composition and temperature. A comprehensive assembly model for these clusters is presented, and electronic structure calculations provide insight into the nature of niobium–niobium bonding within the [Nb₇O₅] core.