Tellurium-Oxygen Compounds

E. Se202Fg, Te202F8, and Other Tellurium-Oxygen-Fluorine Compounds... 

The Si=Si double bonds of the five-membered ring compounds 154-156 also exhibit a similar low reactivity and, for example, are not attacked by atmospheric oxygen. However, the tellurium compound 156 is photochemically labile and decomposes on exposure to daylight with deposition of tellurium142. 

The extreme sensitivity of tellurols to oxygen make the isolation of these tellurium compounds difficult. Therefore, tellurols are almost always used in situ. In the literature, tellurols are sometimes claimed to be the product of the reduction of diaryl ditelluriums in ethanol as the reaction medium. Tellurols are probably present under these conditions in equilibrium with the tellurolates. Whether the tellurols or the tellurolates are the reactive species, for instance, in addition reactions to carbon-carbon multiple bonds, cannot be decided without additional studies. Benzenetellurol, formed in situ by methanolysis of phenyl trimethylsilyl tellurium, was much less reactive towards acetylenes than the tellurium compound obtained by reduction of diphenyl ditellurium with sodium borohydride in ethanol5. 

Tellurolates were formed when bisfbenzoyl] tellurium compounds were reacted with primary amines, with secondary amines, or with potassium ethoxide in dichloromethane at — 30° under an atmosphere of argon. The tellurolates were oily substances that were too unstable thermally and towards oxygen for purification. They were alkylated to 7e-alkyl tellurolobenzoates or oxidized to ditellurium derivatives3. 

The extreme sensitivity of tellurolates to moisture and oxygen makes the isolation of these tellurium compounds difficult. Therefore, tellurolates are almost always prepared under an inert atmosphere and used in situ. 

Methoxyphenyl tellurium compounds with cyclic ether or lactone functionalities in the imposition to the carbon atom linked to tellurium were detellurated by tributyltin hydride in oxygen-free toluene with elimination of the aryltelluro group2. 

Diaryl tellurium dichlorides are also obtained when air or oxygen is bubbled through a suspension of the diaryl telluriums in aqueous hydrochloric acid (Vol. IX, p. 1064) or when the diaryl tellurium compounds are electrochemically oxidized in hydrohalic acid solutions6. 

Exposure of neat dialkyl tellurium compounds or their solutions to air or pure oxygen led to the formation of dialkyl tellurium oxides. Diphenyl tellurium dissolved in diethyl ether is only slowly oxidized by oxygen3. 

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