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

With the synthesis of new perfluoroalkyltellurocarbonyls, their precursors and cyclic dimers additional valuable information about these classes of co mpounds 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)(2)C=Te could not be detected as it dimerises quantitatively to the cor responding 1,3-ditelluretane. It was possible to isolate R(F)C=Te (R=C2F5, n-C3F7) at -196 degrees C, but slightly above this temperature, these compo unds cyclise to mixtures of cis/trans 1,3-ditelluretanes. The tellurocarbon yls undergo [4+2]-cycloaddition reactions with 2,3-dimethylbutadiene provid ing the corresponding tellurins. The reaction between RTeTeR and mercury yi elded Hg(TeR)(2) which have been converted with iodine in CH2Cl2 solution t o 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 b y chlorination of tetrafluoro-1,3-ditelluretane: 1,3-dichloro-2,2,4,4-tetra fluoro-1 lambda(4),3 lambda(4)-ditellurabicyclo[1.1.0]butane. It is only st able below -20 degrees C and rearranges almost quantitatively at room tempe rature to ClF2CTeTeCF2Cl.