Theoretical ab initio study of Xenon pentafluoride anion. Mechanism of Xenon pseudorotation

Ab initio calculations have been performed on XeF5− anion at the MP2 and CCSD(T) levels with a large basis set. Four extrema have been optimized and characterized by frequencies analysis. We find the absolute minimum to be of D5h symmetry in accordance with the experimental data; the theoretical vibrational spectrum of this minimum is in good agreement with the experimental one. Three other extrema are found to be higher in energy depending on the angular separation of the Xenon lone pairs as predicted by the VSEPR theory. Finally the characterized transition state has been found to belong to the Xenon pseudorotation pathway.