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)C
Te 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 Tex(C2F5)2(x= 1 or 2) or Te[(CF3)2CF]2 and Me3SnH in good yield.