Ditellurium Compounds

The ditellurium compounds were treated with sodium borohydride and the tellurols reacted with methyl iodide to produce 9-carboranyl methyl tellurium derivatives1 (see p. 5). 

Lithium benzenetellurolate8,9 and lithium ethanetellurolate10 were more conveniently obtained from the corresponding diorgano ditellurium compounds and lithium at room temperature with anhydrous diethyl ether or tetrahydrofuran as reaction medium. The reductions are complete when the orange-red color of the ditellurium derivatives has faded to pale yellow. 

Sodium Benzenetellurolate1 This reaction must be carried out under nitrogen or argon in an apparatus suitable for work with liquid ammonia2. A filtered suspension of 0.35 g (15 mmol) of sodium in 25 ml of liquid ammonia is added to a suspension of 3.1 g (7.5 mmol) of diphenyl ditellurium in 15 ml of liquid ammonia. The blue color of the sodium/ammonia solution changes rapidly to yellow. The reaction is complete when the solid ditellurium compound has disappeared. The reaction mixture is then filtered, the ammonia is evaporated, and the grey residue is washed with petroleum ether yield 3.1 g (95%). 

The reduction of diorgano ditellurium compounds by sodium borohydride is applicable to both dialkyl, divinyl and diaryl ditellurium compounds (Table 2 p. 166). 

The reduction of ditellurium compounds with sodium borohydride is suitable for the generation of sodium tellurolates derived from carbohydrates4. 

When polymeric ditellurium compounds were reduced with sodium borohydride in methanol5, in ethanol6,7 or in ethanol/benzene8, disodium ditellurolates were formed. 

Tabic 2 Sodium Tellurolates from Diorgano Ditellurium Compounds and Sodium Boro-... 

Tellurolates generated from ditellurium compounds and sodium borohydride served as catalysts for the following reactions. 

Diaryl ditellurium compounds, when heated in pyridine, ethanol, or acetic acid with selenium dioxide, produced the corresponding bis[aryltelluro] selenium and derivatives of these compounds with oxygen bonded to tellurium and selenium4. 

Diaryl ditellurium compounds react with iron carbonyls in benzene solution to form dinuclear, arenetellurolato-bridged iron complexes1 7... 

The oxidative addition of diaryl ditellurium compounds to mmv-[carbonylbis(triphenyl-phosphine)chloroiridium] in dry toluene was investigated by visible spectrophotometry. The product of the reaction with bis[4-cthoxyphenyl] ditellurium was isolated as a light-brown solid. The arrangement of the six ligands around the iridium atom is not known2. 

Diaryl ditellurium compounds and tetrakis[triphenylphosphane]palladium reacted in benzene to form the dinuclear complex bis[/r-arenetellurolato]bis[arenetellurolato]bis[tri-phenylphosphane]dipalladium3. 

The complexes formed from diorgano ditellurium compounds and copper(I) halides in ethanol/acetonitrile are postulated to have intact Te-Te bonds1,3,4. 

When diorgano ditellurium compounds dissolved in an organic solvent are shaken with elemental mercury, the mercury inserts into the Tc-Te bond. 

Organo tellurium halides, also named organo tellurenyl halides, are in principle easily accessible through controlled halogenolysis of diorgano ditellurium compounds. However, 2-naphthyl tellurium iodide, prepared in 19592 from bis[2-naphthyl] ditellurium and iodine, remained the only compound of this type until 1971/72, when a series of ortho-carbonyl substituted phenyl tellurium halides were synthesized3-4. Aryl tellurium halides without substituents in the ortho-position to tellurium were isolated and characterized in 1975s. 

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. 

Aryl tellurium halides are easily reduced to diaryl ditellurium compounds by sodium sulfide7, sodium disulfite8, zinc in refluxing toluene9, or hydrazine hydrate10 (p.273). 

Treatment of aryl tellurium halides with base (ethanolic potassium hydroxide6, aqueous sodium hydroxide7, triethylamine8, tris[< -propyl] phosphite8, triphenylphosphane8) leads to the formation of diaryl ditellurium compounds (p. 273). In the hydrolytically induced disproportionation reactions, aryl tellurinic acids are the other tellurium-containing products7,9. 

Phenyl, 4-methoxyphenyl, and 4-ethoxyphenyl tellurium thiocyanates are known only in the form of their complexes with thiourea1,2 ethylenethiourea3, triphenylarsine oxide, 3-methylpyridine, 3-methylpyridine /V-oxidc, or 4-methylpyridine Af-oxide2. These compounds were prepared from the diaryl ditellurium compounds, thiocyanogen, and the ligands2. 

A large number of symmetrical diorgano ditellurium compounds with aliphatic or aromatic groups have been prepared (IX, p. 1106). 

Hydrogen telluride, generated in situ from aluminum telluride in aqueous tetrahydrofuran containing sulfuric acid, reacted with aliphatic aldehydes to produce dialkyl ditellurium compounds in yields of aproximately 50%. Strong acids are required to obtain acceptable yields of ditellurium compounds. Weak acids (acetic acid, chloroacetic acid) reduce the yields to approximately 10%. In a basic medium (triethylamine), no ditellurium derivative was formed the major product was the alcohol. 

In all these reactions alkanols were formed in yields of a few percent. The ditellurium compounds are postulated to be the products of the reaction of hydrogen telluride with the telluroaldehydes that are formed as intermediates from the aldehydes and hydrogen telluride1. 

Aliphatic halides react easily with disodium ditelluride to yield dialkyl ditellurium compounds. Although a systematic investigation of this reaction has not yet been carried out, primary alkyl chlorides, bromides and iodides, and secondary alkyl bromides produce the corresponding dialkyl ditellurium derivatives in good yields. 

Ditelluride12 and tetratelluride13 dianions were also generated electrochemically and were subsequently alkylated to ditellurium compounds. 

This method was used to prepare the following dialkyl ditellurium compounds di(n-alkyl) ditelluriums2... 

Z,Z)-Bis[2-phenylethenyl] Ditellnrium2 6.4 g (50 mmol) tellurium, 42 g (750 mmol) potassium hydroxide. 22.6 g (100 mmol) tin(II) chloride dihydrate, 10,2 g(100 mmol) phenylacetylene, 20 ml toluene, 60 ml water, and 1.2 g Adogen 464 are vigorously stirred and kept at 80° to 97° for 7 h. The organic layer is separated and the aqueous layer is extracted with benzene. The benzene is evaporated under reduced pressure and the residue dissolved in a small volume of diethyl ether. This solution is poured into 200 m/ isopropanol. The mixture is kept in the refrigerator for 3 days. The yellow crystals of the bis[2-phenylethenyl] tellurium are separated from the red needles of the ditellurium compound, that melted at 82 (yield 6%). 

Alkanetellurolates, that can be obtained from an organic lithium compound or a Grignard reagent and tellurium, are oxidized to dialkyl ditellurium compounds on contact with air. Di-t-butyl ditellurium, that is difficult to prepare by other routes, was obtained by this method in excellent yield1 2. The reaction of /-butyl magnesium chloride with tellurium proceeded in THF solution only in the presence of hexamethylphosphoric triamide2. 

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