Diorgano Tellurium Oxides

Diorgano tellurium dihalides stirred with silver selenocyanate or potassium selenocyanate in chloroform or acetone produce diorgano tellurium bis[selenocyanates]  

Diphenyl tellurium azide iodide and diphenyl tellurium cyanate iodide reacted with silver thiocyanate in chloroform with exchange of iodide for thiocyanate s. 

Dialkyl, diaryl, alkyl aryl, and heterocyclic tellurium oxides are known. Most of these compounds are white solids that are soluble in sodium hydroxide. Diorgano tellurium oxides appear to be oxidized by atmospheric oxygen. Their exposure to air should be minimized. The protonation constant of dimethyl tellurium oxide in water was found to be 6 (pKg) and of bis[4-methoxyphenyl] tellurium oxide in acetonitrile 14.9 . The barrier to inversion for dihydrogen tellurium oxide (H2Te = 0), the parent compound of diorgano tellurium oxides, was determined as 92.4 kJ/mol (22.0 kcal/mol) by extended Hiickel calculations . 

Diorgano tellurium oxides are closely related to diorgano tellurium dihydroxides. The reaction of diorgano tellurium oxides with water produces diorgano tellurium dihydroxi- 

Irgolic Organo Tellurium Compounds with 2 Te —C Bonds or 1 Te = C Bond 

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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 tellurium oxides are reduced by hydrazine hydrate to diorgano tellurium compounds. The diorgano tellurium oxides are obtained as the primary products of the reactions of arenetellurinyl acetate or trifluoroacetates with olefins in chloroform, 1,2-dichloroethane, or acetonitrile as reaction media. When the olefin has a hydroxyl group in a f -, y-, or fi-position to the double bond, the addition of the tellurium compound to the double bond is followed by cyclization forming oxacycloalkane derivatives1. 

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). 

Alkyl aryl telluriums and diaryl telluriums react with anhydrous (V-chloro-/V-sodioarenesulfonamides in refluxing chloroform in the presence of 18-crown-6 to yield diorgano tellurium arenesulfonimides1. When the reactions are carried out with the hydrated sulfonamides in methanol, diorgano tellurium oxides are formed1. 

The diorgano tellurium oxides or dihydroxides need not be isolated. Treatment of diorgano tellurium dihalides with silver oxide2,3 or ammonia and silver nitrate4 forms solutions of diorgano tellurium dihydroxides, which can be immediately reacted with hydrohalic acids. 

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. 

Diorgano telluriums were oxidized by chloramine-T3, Ar- ch 1 o r o s ucci ni m ide4, and N-bromosuccinimide4,5. Hydrolysis of the oxidation products produced diorgano tellurium oxides. 

Diorgano tellurium oxides are reported to be slowly oxidized by atmospheric oxygen to high-melting diorgano tellurium dioxides9. This oxidation can be carried out in a controlled manner with sodium periodate in aqueous methanol7,10,1. ... 

Diorgano tellurium oxides react with nitric and perchloric add producing diorgano tellurium hydroxide perchlorates1, diperchlorates2, hydroxide nitrates3, or dinitrates4. 

Sulfonic acids3 and their anhydrides4 react with diorgano tellurium oxides to produce diorgano tellurium disulfonates (p. 620). 

Diorgano tellurium oxides condense with compounds containing activated methylene groups to form diorgano tellurium ylides2,3. 

Diorgano tellurium oxides are reported to decompose when heated under vacuum5. Such decompositions have been used to convert the alkyl group in alkyl phenyl tellurium oxides to alkenes (see below). The Te —C (aliphatic) bond in alkyl phenyl tellurium oxides is cleaved by 3-chloroperoxybenzoic add6. 

Several reaction sequences have been explored in which diorgano tellurium oxides are intermediates in the transformation of organic compounds. The following transformations have been achieved ... 

The oxidation of diorgano tellurium oxides with sodium periodate appears to produce diorgano tellurium dioxides11 12. 

Diorgano tellurium oxides and organic compounds with an activated methylene group condensed in chloroform1 or benzene2 to produce diorgano alkylidene tellurium compounds. 

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