By Transalkylation or Transarylation

Neat dimethyl tellurium and trifluoromethyl iodide or pentafluoroethyl iodide reacted under UV irradiation to give bis[perfluoroalkyl] telluriums and methyl perfluoroalkyl telluriums. The bis[perfluoroalkyl] telluriums could not be completely separated from the unsymmetrical tellurium compounds by trap-to-trap distillation. The yields are strongly influenced by the molar ratios of the reactants. The products were isolated as yellow, odorless liquids.  

The presence of an approximately equimolar amount of triethylamine in the reaction mixture binds the methyl iodide formed in the reaction, shifts the equilibrium of the reaction toward the products, and prevents the quatemization of diorgano tellurium products. Whereas pentafluoroethyl iodide requires photochemical stimulation, hep-tafluoroisopropyl iodide does not.  

Methyl Pentafluoroethyl Tellurium A mixture of 9.0 g (57.1 mmol) dimethyl tellurium and 17.9 g (72.8 mmol) pentafluoroethyl iodide is treated with 2.3 g (22.8 mmol) triethylamine at — 78° in a flask equipped with a low-temperature reflux condenser. The mixture is allowed to warm to 20 and then irradiated for 3 h with the reflux condenser kept at — 35°. The mixture is fractionally distilled to give methyl pentafluoroethyl tellurium as a light-yellow liquid that is stable toward water but easily oxidized yield 63% b.p. 42°. 

Heptafluoroisopropyl methyl tellurium (b.p. 86°) was similarly obtained in 79% yield however, the reactants were mixed at 0° and then kept at 70° for 18 hours without irradiation.  

For the preparation of methylpentafluorophenyl tellurium, the irradiation of an equimolar mixture of dimethyl tellurium, pentafluorophenyl iodide, and triethylamine at 20° in trichlorofluoromethane is recommended. The methyl pentafluorophenyl tellurium can be separated by vacuum distillation from bis pentafluorophenyl tellurium. Bis[pentafluoro-phenyl] tellurium is best obtained by heating the stoichiometrically required amounts of the reagents slowly (2°/min) to 130°. After six hours the mixture is distilled and the residue sublimed.  

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