The preparation of bis(perfluoroethyl) tellurium difluoride and dichloride, trans perfluoroethyl tellurium monochloride tetrafluoride, trans bis(perfluoroethyl) tellurium tetrafluoride; and the preparation and X-ray crystal structure of perfluoroethyl tellurium trifluoride

The reaction of (C₂F₅)₂Te and XeF₂ in a slurry of SO₂ClF yielded (C₂F₅)₂TeF₂ essentially quantitatively. Chlorine and (C₂F₅)₂Te gave (C₂F₅)₂TeCl₂. Both (C₂F₅)₂TeF₂ and (C₂F₅)₂TeCl₂ were assigned a trigonal bipyramidal geometry, on the basis of their ¹⁹F nmr and vibrational spectra, with the lone pair and C₂F₅ groups in equatorial, and the halogens in the axial positions. Perfluoroethyl tellurium trifluoride was prepared essentially quantitatively by the reaction of C₂F₅TeTeC₂F₅ and XeF₂ in liquid SO₂F₂. The generally inert SO₂ClF was found to react with C₂F₅TeTeC₂F₅ to give C₂F₅TeCl_xF_3−x, and sulphur dioxide. The structure of C₂F₅TeF₃ was determined by X-ray diffraction. The crystals are tetragonal with a = 10.129(4), c = 25.561(6) Å, and Z = 16. The structure was refined in space group I4₁/a to a conventional R factor of 0.051 for 901 observed reflections with I ≥ 3σ(I). Each tellurium atom is surrounded by two terminal fluorine atoms and two bridging fluorine atoms and a C₂F₅ group in an axial position around the apex of a distorted square pyramid. The square-pyramidal units are linked by symmetrical cis bridging atoms into endless chains with bridging angles of 180° and 177°. The geometry of the (C₂F₅TeF₄) group is consistent with steric activity of the non-bonded electron pair. The ¹⁹F nmr and Raman spectra of C₂F₅TeF₃ were recorded and the Raman spectrum assigned. Trans-C₂F₅TeClF₄ was prepared by the reaction of C₂F₅TeTeC₂F₅, and an excess of ClF. The trans octahedral geometry of C₂F₅TeClF₄ was unambiguously assigned from its ¹⁹F nmr and vibrational spectra. A mixture of trans-(C₂F₅)₂TeF₄ and trans-C₂F₅TeClF₄ was obtained from the reaction of (C₂F₅)₂Te and an excess of ClF. Trans geometry of (C₂F₅)₂TeF₄ was unambiguously assigned from its ¹⁹F nmr spectrum.