Niobium and tantalum octahedral Halides: Vibrational properties and Intra-Cluster interactions

IR and Raman spectroscopies are important characterisation methods for Nb and Ta octahedral halide clusters [(M6X12X6a)-X-i](x) (M = Nb, Ta; X = Cl, Br; x = 4-, 3-, 2-; i - inner, bridging ligand belonging to the cluster core, a - ausser or apical terminal ligand) and the polymeric Ta6I14. The structural and spectroscopic data of these compounds (x = 4-) and their corresponding {M6X12}(2+) core clusters were systematically investigated and analysed by means of quantum chemical calculations. The intra-cluster interactions were studied in details by means of Natural Bond Orbital and Bader's Atoms-In-Molecules theory analyses, and the results were related to the spectroscopical features, in particular to the composition of the main vibrational normal modes in terms of the contribution of the internal coordinates.

Automated summary

IR and Raman spectroscopies are important for characterizing the structures and spectroscopic properties of Nb and Ta octahedral halide clusters and the polymeric Ta6I14. Quantum chemical calculations and analyses of intra-cluster interactions were performed to understand the relationship between the structural and spectroscopic data, particularly the main vibrational normal modes.