Molecular Niobium Precursors in Various Oxidation States: An XAS Case Study

Although X-ray absorption spectroscopy (XAS) has become an indispensable tool in characterization of solid-state materials, it is less of a staple in molecular chemistry of niobium. Scattering X-ray techniques remain relatively unexplored for the systematic study of molecular niobium compounds. Here, we use XAS to probe the niobium environment in commonly used Nb precursors in +V, +IV and +III oxidation states. Apart from laying out the guidelines for identification of niobium oxidation states, we correlate our data with density functional theory (DFT) models to provide further structural insight. Of particular note, we are able to shed light on the nature of the commonly-used and catalytically competent NbCl3(DME), which had not been previously characterized structurally despite its prevalence in Nb chemistry.