Trifluorotelluroacetyl fluoride, its cyclic dimer and precursors: preparation, characterisation and reactivity

Abstract

With the synthesis of CF₃(F)CTe, the second, non-resonance stabilised perfluorinated telluracarbonyl has been isolated and characterised by gas-phase IR and mass spectrometry. It was prepared via pyrolysis of the novel compound Me₃SnTeC₂F₅ at 500 °C, 10^–3 Torr in 40–50% yield. The compound CF₃(F)CTe is only stable at –196 °C and dimerises quantitatively a few degrees above this temperature to the corresponding mixture of cis/trans-2,4-bis(trifluoromethyl)-2,4-difluoro-1,3-ditelluranes which cannot be separated by physical nor chemical procedures. Their reaction with BX₃(X = Cl or Br) yielded chlorinated and brominated cis/trans-1,3-ditelluretanes. Additionally the telluracarbonyl undergoes a cycloaddition reaction with 2,3-dimethylbutadiene forming 2-fluoro-3,6-dihydro-4,5-dimethyl-2-trifluoromethyltellurin. The required precusors for the synthesis of the perfluorinated telluracarbonyls TeR₂ and Te₂R₂ were prepared by three different methods. The compounds Me₃SnTeR [R = C₂F₅ or (CF₃)₂CF] were obtained from Te_x(C₂F₅)₂(x= 1 or 2) or Te[(CF₃)₂CF]₂ and Me₃SnH in good yield.