From Tellurium Tetrachloride and Organometallic Compounds

Organo magnesium halides and organo lithium compounds are readily accessible alkylation and arylation reagents. However, they have little practical importance for the preparation of diorgano tellurium derivatives. Tellurium tetrachloride cannot be alkylated or arylated stepwise to give, for instance, diorgano tellurium dihalides, which could 

FjCs-Mgar (Li ) bis pentafluorophenyl] tellurium 2-F5C6-F4C5-Li bis[nonafluoro-2-biphenylyl] tellurium l-c, H,-MgBr bis[I-naphthyl tellurium  

For example, di-tert.-butyl tellurium was isolated in 76% yield by vacuum distillation as the product of the reaction between 20.2 g (50 mmol) tellurium tetrachloride in lOOw/ tetrahydrofuran at —78° and 187 m/ of a 1.6 molar solution of rcr/.-butyl lithium (300 mmol) in pentane. The reaction was carried out with standard Schlenk techniques in the dark . 

The reactions between Grignard reagents and tellurium dihalides frequently reported in the older literature (Vol. IX, p. 1051) produced mixtures of diaryl tellurium products and other organic tellurium compounds that were difficult to separate. Tellurium dihahdes are rather unstable compounds with a strong tendency to disproportionate to tellurium and tellurium tetrahalides. The Grignard reagents, which had to be used in excess of the stoichiometri-cally required amounts, then reacted with the tellurium (p. 172) and the tellurium tetrahalide and probably not with the tellurium dihalide. 

The selective alkylation of tellurium tetrachloride and tetrabromide to a diorgano tellurium compound was achieved with bis[trifluoromethyl] mercury and the bipyridyl adduct of bis[pentafluoroethyl] mercury.  

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