Diorgano Tellurium Dioxides

Diorgano tellurium oxides are reported to be slowly oxidized by atmospheric oxygen to high-melting diorgano tellurium dioxides . This oxidation can be carried out in a controlled manner with sodium periodate in aqueous methanoF ... 

The oxidation of diorgano tellurium oxides with sodium periodate appears to produce diorgano tellurium dioxides . ... 

Dialkyl, alkyl aryl, and diaryl tellurium dichlorides were reduced by thiourea dioxide in a 2 molar aqueous solution of sodium hydroxide to the corresponding diorgano tellurium compounds4,5. The tellurium species actually reduced are the diorgano tellurium oxides or dihydroxides that are formed from the dichlorides in the basic medium. 

Diorgano Tellurium5 (Thiourea Dioxide Method) A mixture of 2 mmol of the diorgano tellurium dichloride and 10 ml of 2 molar aqueous sodium hydroxide solution is stirred for 15 min at 20°. Then, 0.432 g (4 mmol) thiourea dioxide and 10 m/ petroleum ether (30-60°) are added. The mixture is stirred at 20° until it becomes clear. The phases are separated. The aqueous phase is extracted three times with diethyl ether. The combined organic phases are dried with anhydrous magnesium sulfate, the dried mixture is filtered, and the solvent evaporated from the filtrate. The residue is placed on a silica-gel column. The product is eluted with petroleum ether. 

The reduction of diorgano tellurium dichlorides by thiourea dioxide in aqueous sodium hydroxide solution proceeds via diorgano tellurium oxides or dihydroxides as intermediates (see page 432). 

Diorgano tellurium compounds can be easily converted to diorgano tellurium dihalides in reactions with sulfuryl chloride, bromide, and iodide. Carbon tetrachloride, dichlorometh-ane, diethyl ether, petroleum ether, or benzene have been used as reaction media. Chlorinations with sulfuryl chloride, a liquid reagent, avoid the use of gaseous chlorine. Required amounts of sulfuryl chloride can be more easily measured than those of chlorine. Sulfur dioxide formed during the reaction escapes the reaction mixture as a gas, thus facilitating the isolation of the product. For these reasons, sulfuryl chloride has been frequently used, whereas sulfuryl bromide and iodide5-6 have been only infrequently employed. 

Diorgano tellurium dihalides react with reducing agents (sodium sulfide, sulfites, hydrazine, thiourea dioxide, sodium borohydride) under mild conditions to give the corresponding diorgano tellurium derivatives in high yields. 

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. ... 

Diorgano tellurium oxides are reduced to diorgano telluriums by hydrazine hydrate sulfur dioxide", phenyl trimethylsilyl selenium, formamide , sodium borohydride, and thiourea dioxide . 

Oxidation of 4-methoxyphenyl dodecyl tellurium with /er/.-butyl hypochlorite in benzene gave a 1 2 1 mixture of the diorgano tellurium, its oxide, and its dioxide. ... 

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