Tellurium Dicarboxylates

Diorgano tellurium dicarboxylates were prepared from dialkyl and diaryl tellurium derivatives. Aliphatic carboxylic acids, aromatic carboxylic acids, their sodium or silver salts, and carboxylic acid anhydrides were used as reagents. Dicarboxylic acids such as succinic acid and phthalic acid were reported to give monomeric carboxylates when 

The diorgano tellurium dicarboxylates are white, crystalline materials that are soluble in organic solvents and stable towards atmospheric agents. Diaryl tellurium diacetates can be boiled in water without decomposition. However, bis[trifluoromethyl] tellurium bis trifluoroacetate] was reported to be moisture-sensitive. Aqueous sodium hydroxide converts diaryl tellurium dicarboxylates to diaryl tellurium oxides or dihydroxides . Thermal gravimetric analysis of diaryl tellurium dicarboxylates indicated that these compounds lose carbon dioxide at 240-260° and form the tetraaryl tellurium derivatives. The tetraorgano tellurium compounds decompose slowly to the diaryl tellurium compounds and hydrocarbons.  

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A convenient single-step method for the preparation of diaryl tellurium dicarboxylates in 82 to 92% yields involves the reactions of the diaryl tellurium with hydrogen peroxide and carboxylic acids2,3. The reaction probably proceeds via diaryl tellurium oxides as intermediates. Carboxylic acid anhydrides can be used instead of the carboxylic acids. 

No pure tellurium derivatives were obtained when the sodium salts of maleic, fumaric, formic, isophthalic, or terephthalic acids were shaken with diaryl tellurium dichlorides2. Diorgano tellurium dichlorides stirred with silver carboxylates in dioxane, acetone, chloroform, benzene, or toluene precipitated silver chloride. Evaporation of the filtrate yielded diorgano tellurium dicarboxylates. 

The isolation of the silver carboxylates can be avoided. Stirring and refluxing a mixture of a diorgano tellurium dichloride, a carboxylic acid, and silver oxide in benzene or acetone gives diorgano tellurium dicarboxylates in good yields. Silver carboxylates were proposed as intermediates4. 

Diaryl tellurium dicarboxylates were prepared in good yields from diaryl tellurium dichlorides and anion exchange resins such as Amberlite IR45 and Amberlite IR400 in their carboxylate form. The carboxylate resins were obtained by treating the resins in the OHe-form with carboxylic acids or the resins in the Cle-form with sodium carboxylates4. 

Diaryl tellurium oxides react with two molar equivalents of carboxylic acids in carbon tetrachloride, chloroform, or isopropanol to form diaryl tellurium dicarboxylates in almost quantitative yields. 

Diorgano tellurium oxides react with an equimolar amount or an excess of a carboxylic acid anhydride to produce diorgano tellurium dicarboxylates in quantitative yields. Chloroform or excess carboxylic acid anhydride served as reaction media. The excess anhydride can be destroyed by boiling in water1. 

Diaryl tellurium dicarboxylates refluxed in chloroform or toluene with carboxylic acid chlorides produced diaryl tellurium dichlorides and carboxylic acid anhydrides4-6. 

Heating diaryl tellurium dicarboxylates in acetonitrile with iodine or bromine in the presence of potassium fluoride produced aryl halides in low yields2. 

Bis[4-mcthoxyphenyl] tellurium dicarboxylates heated with copper(I) cyanide in DMF at 160J produced 4-methoxyphenyl cyanide in very low yields2. 

Bis[4-methylphenyl] tellurium hydroxide carboxylates were obtained when the diaryl tellurium dichloride was reacted with silver caprate or silver caproate in dioxane. It is likely that the diaryl tellurium dicarboxylates, the expected products of these reactions, were hydrolyzed during the reaction or on recrystallization2. 

Diorgano tellurium dichlorides and dibromides react with silver carboxylates " " or sodium carboxylates with formation of diorgano tellurium dicarboxylates. The same conversion was accomplished by shaking diaryl tellurium dichlorides with an Amberlite IR 45 resin in the carboxylate form or by treating bis[trifluoromethyl] tellurium dihalides with trifluoroacetic anhydride. ... 

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