From Aryl Tellurium Trihalides

Bis[4-propoxyphenyl] Ditellurium [Sodium Sulfide Method] 3.7 g (0.01 mol) of 4-propoxyphenyl tellurium trichloride are thoroughly ground with 20 g (0.08 mol) of sodium sulfide nonahydrate, the mixture is heated with stirring on a boiling water bath for 30 min, cooled to 20°, and mixed with ice/watcr. The product is extracted with petroleum ether, the extract is evaporated, and the residue is recrystallized from petroleum ether yield 2.3 g (86%) m.p. 84°. 

Bis[4-methylphenyl] Ditellurium [Hydrarine Method] A solution of 3.2 g (0.1 mol) of hydrazine in 20 ml of ethanol is slowly added dropwisc to a refluxing solution of 3.25 g (0.01 mol) of 4-methylphenyl tellurium 

Hydrazine hydrate may be used in place of pure hydrazine  

Bis[2-methylphenyl] Ditellurium [Thiourea Dioxide Method] A mixture of 0.65 g (2.0 mmol) 2-methylphenyl tellurium trichloride and 5 m/of 2 M aqueous sodium hydroxide solution is vigorously stirred at 20° for 15 min. To this mixture are added 0.43 g (4.0 mmol) thiourea dioxide and 5 ml petroleum ether (30-60°). The mixture is stirred at 20° for 15 min. The phases are separated. The organic phase is dried with anhydrous magnesium sulfate, filtered, and the solvent evaporated from the filtrate. The product was isolated in 76% yield. 

4-dimethoxyphenyl] Ditellurium [Hypophosphorous Acid Method] A solution of 37.2 g (0.1 mol) 3,4-dimethoxyphenyl tellurium trichloride in 500 ml absolute ethanol is filtered. To the rapidly stirred filtrate 30 w/ ( 0.3 mol) of 50% aqueous hypophosphorous acid are added at 20° as rapidly as possible. The solution soon sets to a mass of black fibrous crystals. The crystals are collected by filtration, washed with water, and dried in air yield 95% m.p. 136-139°. 

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Table 18 Aryl Organo Tellurium Dichlorides or Dibromides from Aryl Tellurium Trihalides and...

From Aryl Tellurium Trihalides or Diaryl Ditellurium... 

Aryl tellurium bromides and iodides can be obtained by reaction of diaryl ditellurium compounds with an equimolar amount of bromine or iodine, when the solvent is able to dissolve the starting materials but not the aryl tellurium halide. The precipitation of the aryl tellurium halide prevents it from being converted to aryl tellurium trihalides. The aryl tellurium halides thus far isolated and suitable reaction media for their preparation are listed in Table 3 (p. 240). 

The possibility of preparing aryl tellurium halides from equimolar amounts of diaryl ditellurium compounds and aryl tellurium trihalides has hardly been explored. Only phenyl tellurium iodide and 2-biphenylyl tellurium bromide could be obtained by this route. The other aryl tellurium halides (including 3,4-dimethoxyphenyl tellurium chloride) decomposed under the reaction conditions to give diaryl tellurium dihalides and tellurium5. 

Organo tellurium trifluorides, trichlorides, tribromides, and triiodides are known. Aryl tellurium trihalides are generally more stable than alkyl tellurium trihalides. The sensitivity toward atmospheric agents decreases from the trichlorides to the triiodides. Very few organo tellurium trifluorides have been prepared and little is known about their reactivity. The general reactivity of aryl tellurium trihalides decreases from the chlorides to the iodides. 2-Chloroalkyl tellurium trichlorides, products of the addition of tellurium... 

Aryl tellurium trihalides treated with water are converted to arenetellurinyl halides. The susceptibility to hydrolysis decreases from the trichlorides to the triiodides2,3. With basic aqueous solutions (sodium carbonate, sodium hydroxide) tellurinic acids or tellurinic acid anhydrides are formed2 5. 

Aryl tellurium trihalides accept halide ions from tropylium bromide, ammonium halides, phosphonium halides, arsonium halides, sulfonium chlorides, telluronium chlorides, and diphenyl iodonium chloride to form aryltetrahalotellurates(lV)1-5. 

Mixed tetrahalotellurates(IV) result from the combination of an aryl tellurium trihalide with an onium salt containing a halide different from that in the tellurium compound. 

Tropylium aryltetrahalotellurates can be prepared from tropylium bromide and an aryl tellurium trihalide. A more convenient procedure avoiding the laborious preparation of the tropylium bromide uses cycloheptatricne and triphenylmethyl perchlorate2. The product of this reaction can then be converted to the tetrahalotellurate by treatment with hydrohalic acids. 

Aryltellurium trichlorides 5 (R = aryl, X = Cl) are usually yellow, very stable crystalline solids, with a slight odor of hydrochloric acid, which probably arises from the reaction of 5 with the air moisture. Contact of 5 with metallic spatulas, with moist solvents, or prolonged exposure to light must be avoided. These compounds, however, can be handled in the air with no risk of decomposition. Aryltellurium tribromides (5, R = aryl, X = Br) are yellow crystalline solids, and the triiodides (5, R = aryl, X = 1) are dark red solids. The aryltellurium tribromides and triiodides were less explored for synthetic purposes, in contrast to the aryltellurium trichlorides, which were frequently used in several synthetic transformations. The aliphatic tellurium trihalides are less stable than the aromatic ones and were much less studied and used for preparative purposes. 

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 reactivity of the tellurium trihalides decreases from the chlorides to the iodides. The aryl tellurium triiodides do not form diaryl tellurium diiodides and do not react with acetone6. 

Alkyl groups from alkyl aryl telluriums that have a stabilizing nitrogen functionality in the aromatic ring in an orr/zo-position to the tellurium atom are cleaved by bromine, iodine or sulfurylchloride. Aryl tellurium halides or trihalides are produced in these reactions. 

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