Electron Ionization Mass Spectrum of Tellurium Hexafluoride

The electron ionization mass spectrum of tellurium hexafluoride (TeF₆) is reported for the first time. The starting material was produced by direct fluorination of Te metal or TeO₂ with nitrogen trifluoride. Formation of TeF₆ was confirmed through cryogenic capture of the tellurium fluorination product and analysis through Raman spectroscopy. The eight natural abundance isotopes were observed for each of the set of fragment ions: TeF₅⁺, TeF₄⁺ TeF₃⁺, TeF₂⁺, TeF₁⁺, and Te⁺, Te₂⁺. A trend in increasing abundance was observed for the odd fluoride bearing ions, TeF₁⁺ < TeF₃⁺ < TeF₅⁺, and a decreasing abundance was observed for the even fragment series, Te(F₀)⁺ > TeF₂⁺ > TeF₄⁺ > TeF₆⁺, with the molecular ion TeF₆⁺ not observed at all. Density functional theory based electronic structure calculations were used to calculate optimized ground state geometries of these gas phase species, and their relative stabilities explain the trends in the data and the lack of observed signal for TeF₆⁺. (Chemical Equation Presented).