Triorgano Telluronium Salts

Of the ten possible combinations of identical or different alkyl and aryl groups bonded to tellurium, only salts with three different aryl groups have not yet been prepared. Telluronium salts with the following anions have been isolated and characterized  

The telluronium salts behave as 1 1 electrolytes in DMF, DMSO acetone, acetonitrile, and nitrobenzene.  

Attempts were made to resolve triorgano telluronium iodides with three different organic groups bonded to the tellurium atom into optically active isomers Methyl 4-methylphenyl phenyl telluronium iodide was treated with optically active camphorsulfo-nates . The isolated telluronium camphorsulfonates showed mutarotation indicating that the telluroniiun cation had been at least partially resolved. Treatment of the telluronium camphorsulfonates with potassium iodide yielded the racemic telluronium iodides.  

Similar results were obtained with methyl ethyl 4-methoxyphenyl telluronium iodide and 2-(4-chlorophenyl-2-oxoethyl)-l,2,3,4-tetrahydro-2-benzotellurinium bromide . 

Cathodic reduction of tellurium in the presence of methyl iodide in a 1.0 M solution of sodium perchlorate in anhydrous dimethylformamide produced trimethyl telluronium iodide in 80% yield This reaction does not appear to proceed with other alkyl halides. 

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Dialkyl telluriums, diaryl telluriums, and alkyl aryl telluriums are converted to triorgano telluronium salts on reaction with alkyl halides. These alkylations proceed easily with methyl, ethyl, and propyl iodide4, allyl bromide5,6, cyclohexyl iodide7, ethyl bromoace-tate8, and even bromobenzene and iodobenzene4,8. 

Exchange reactions using triorgano telluronium halides as starting materials produced triorgano telluronium salts with the anions Y identified below. These telluronium salts precipitate when aqueous or ethanolic solutions of the reactants are combined. 

Triorgano telluronium salts may lose an organic group to form diorgano tellurium compounds. This reductive elimination is influenced by the nature of the organic groups and the nature of the anion. Methyl" ", benzyl and 2-oxo-2-phenylethyl groups" are especially easy to cleave. However, loss of phenyl iodide was observed when triphenyl telluronium iodide was heated with sodium sulfide nonahydrate . 

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