From Alkyl Aryl Tellurium Compounds

Aryl butyl tellurium compounds reacted with excess sulfuryl chloride, bromine, or iodine in refluxing chloroform with cleavage of the tellurium-butyl bond and formation of the aryl tellurium trihalide  

2-[(4 -Methylphenylimino)methyl]phenyl Tellurium Trichloride A solution of 2.16 g (16 mmol) sulfuryl chloride in 20 ml chloroform is added dropwisc to a vigorously agitated solution of 3.0 g (8 mmol) 2[(4 -methylphcnylimino)methyl]phenyl butyl tellurium in 40 ml chloroform. The yellow precipitate is collected by filtration, washed with diethyl ether, and dried yield 89% m.p. 272-277°. 

Similarly obtained were the corresponding tellurium tribromide (m.p. 293-295° from CHClj/hexane yield 84%) and tellurium triiodide (m.p. 201° from CHClj yield 97%) . 

The Schiff base prepared from 2-formylphenyl butyl tellurium and 1,2-diaminoethane was converted to tellurium trihalides by excess sulfuryl chloride or bromine.  

The reactions of 2-nitrophenyl benzyl tellurium, 2-phenylazophenyl 4-ethoxyphenyl tellurium, and l-oxo-l,3-dihydro-2-benzotellurophene with bromine that produce organo tellurium tribromides, very likely proceed via diorgano tellurium dibromides as intermediates. 

---

Brominations are performed by dropping solutions containing the stoichiometrically required amount of bromine to the stirred solutions of the diorgano tellurium compounds. To prevent tellurium-carbon bond cleavage, which may occur with dialkyl and alkyl aryl tellurium compounds, the reactions should be performed at or below 20°. The likelihood of Te —C bond cleavage decreases from chlorine to iodine. 

The disodium salts of dihydroxyimines reacted similarly with diaryl and alkyl aryl tellurium dichlorides in refluxing benzene3 5. The white, yellow, or brown products were obtained in yields from 60 to 70%. The compounds have sharp melting points and are stable towards atmospheric oxygen and moisture3. 

The preparation of an aryl lithium compound from an aryl halide and an alkyl lithium compound also produces an alkyl halide. The alkyl halide may react subsequently with the lithium arenetellurolate to yield aryl alkyl tellurium compounds. In these cases the tellurolate has only a transitory existence. 

These reactions are of synthetic importance only when the aryl alkyl tellurium compounds are easily accessible. Such aryl alkyl tellurium compounds are obtained when an aryl lithium compound generated from an aryl halide and alkyl lithium is treated with tellurium (p. 154, 387). 

The halogenolysis of dialkyl ditellurium compounds is a convenient method for the preparation of alkyl tellurium trihalides because dialkyl ditellurium compounds are easily accessible through alkylation of disodium ditelluride (p. 258). Diaryl ditellurium compounds generally obtained via reduction of organo tellurium trichlorides (p. 274), serve as starting materials for the syntheses of aryl tellurium tribromides and triiodides (Vol. IX, p. 1156) that are not obtainable from the hydrocarbons and tellurium telrabromide or tetraiodide. 

The preparation of alkyl and aryl tellurium trichlorides from ditellurium compounds is more conveniently carried out with thionyl chloride or sulfuryl chloride instead of gaseous chlorine. 

Primary and secondary alcohols may serve as the source of alkyl groups in the preparation of aryl phenyl tellurium compounds. Phenyl tellurium cyanide, conveniently obtained from diphenyl ditellurium (p. 368), reacted smoothly with alcohols in dichloromethane in the presence of tributylphosphane. The alkyl phenyl telluriums were obtained in yields ranging from 32 to 78%. Triphenylphosphane or triethyl phosphite did not catalyze these reactions2. 

Diorgano tellurium dihalides were prepared in this manner from dialkyl, alkyl aryl, and diaryl tellurium compounds, and from tellurium heterocycles. However, 1-oxo-1,3-dihydro-2-benzotellurophene experienced ring cleavage when reacted with sulfuryl chloride7. 

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 compounds" The tellurium species actually reduced are the diorgano tellurium oxides or dihydroxides that are formed from the dichlorides in the basic medium. 

Diaryl ditellurium compounds were similarly obtained from the following aryl alkyl tellurium dihalides ... 

---