Perfluoroalkyltellurocarbonyl fluorides, their cyclic dimers and perfluoroalkanetellurenyl iodides: preparation and reactivity

Abstract

With the synthesis of new perfluoroalkyltellurocarbonyls, their precursors and cyclic dimers additional valuable information about these classes of compounds has become available. They were prepared via pyrolysis of Me₃SnTeCF(CF₃)₂ and the novel compounds Me₃SnTeR (R = n-C₃F₇, n-C₄F₉). The monomer (CF₃)₂CTe could not be detected as it dimerises quantitatively to the corresponding 1,3-ditelluretane. It was possible to isolate R(F)CTe (R = C₂F₅, n-C₃F₇) at −196 °C, but slightly above this temperature, these compounds cyclise to mixtures of cis/trans 1,3-ditelluretanes. The tellurocarbonyls undergo [4 + 2]-cycloaddition reactions with 2,3- dimethylbutadiene providing the corresponding tellurins. The reaction between RTeTeR and mercury yielded Hg(TeR)₂ which have been converted with iodine in CH₂Cl₂ solution to RTeI. With AgCN the in situ prepared iodides form RTeCN (R = CF(CF₃)₂, n-C₃F₇, n-C₄F₉) in good yields. A new type of compound has been synthesized by chlorination of tetrafluoro-1,3-ditelluretane: 1,3-dichloro-2,2,4,4-tetrafluoro-1λ⁴,3λ⁴-ditellurabicyclo[1.1.0]butane. It is only stable below −20 °C and rearranges almost quantitatively at room temperature to ClF₂CTeTeCF₂Cl.