From Aryl Tellurium Halides

2-Formylphenyl tellurium bromide and benzenethiol in refluxing pyridine produced 2-formylphenyl phenylthio tellurium.  

2-Formylphenyl Phenylthio Tellurium 2.5 g (8.0 mmol) of 2-formylphenyl tellurium bromide are dissolved in 25 nj/ of pyridine, 0.88 g (8.0 mmol) of benzenethiol are added, and the mixture is heated under reflux for 2 h. The resultant mixture is poured into aqueous hydrochloric acid/ice and extracted with chloroform. The organic phase is separated, dried, filtered, and chloroform is distilled from the filtrate. The residue is recrystallized from hexane/benzene yield 1.4 g (50%) m.p. 73°. 

2-(Phenylazo)phenyl tellurium chloride reacted with sodium dithiocarbamates at room temperature to give 2-(phenylazo)phenyl dithiocarbamato tellurium compounds.  

2-(Phenylazo)phenyl Dialkylditfaiocarbamato Tellurium A solution of the sodium dialkyldithiocarbamate (1.03 mmol) in 15 m/ dry methanol is added under an atmosphere of nitrogen to a stirred solution of 2-(phenylazo)phenyl tellurium chloride (0.35 g, 1.0 mmol) in dichloromethane (25 ml). The mixture is stirred for 20 min at 20°. The solvents are removed on a rotary film evaporator. Dichloromethane is added to the residue. The mixture is vigorously stirred and the solution is filtered to remove the sodium chloride. 

The solvent is evaporated from the filtrate. Methanol (5 ml) is added to the residue. The mixture is stirred and then filtered. The filter cake is recrystallized from methanol. 

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Additional diaryl ditellurium derivatives were obtained from aryl tellurium halides as shown below ... 

From Aryl Tellurium Halides 10.1. With Organometallic Compounds... 

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. 

The coordinatively unsaturated aryl tellurium halides interact with electron-donor ligands to form complexes. The aryl tellurium halides prepared from diphenyl ditellurium and halogens were used in situ. Thiourea, selenourea (X = Cl, Br)3, tetramethylthio- and... 

The reduction of aryl tellurium halides to the corresponding diaryl ditelluriums is of synthetic utility only for compounds with stabilizing substituents in the ortho-position to tellurium (p. 242). Diaryl ditellurium products are obtained in excellent yields from such aryl tellurium halides upon reduction with sodium disulfite3, zinc4, hydrazine hydrate5, or sodium borohydride6, or upon treatment with aqueous potassium hydroxide3. 

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. 

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. 

Aryl tellurium trichlorides and tribromides react with terminal and internal linear olefins and with cycloalkenes to produce aryl 2-chloroalkyl tellurium dihalides. The halide ion and the aryldichlorotelluro group approach the olefin from opposite sides of the plane defined by the atoms bonded to the olefinic carbon atoms. These arm-additions yield threo-addition products from (Z)-olefins, and erythro-products from (E)-olefins4 6. 

Among the many recent reports concerning telluranes, little is to be found of significant organic chemical interest, though a synthesis of biaryls from bis(aryl)tellurium dihalides or diary] tellurides by treatment with degassed Raney nickel is notable. Some leading references are 2%, 297, and also others discussed in the Sulphenyl Halides section. 

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). 

Unsymmetrical diaryl tellurium compounds generally cannot be prepared from arenetel-lurolates and aromatic halides under conditions suitable for aliphatic halides. Special conditions appear to be needed. Several methods have thus far been discovered for the arylation of arenetellurolates. 

Diaryl tellurium dichlorides, obtainable from aromatic compounds and tellurium tetrachloride, react with excess bromine or iodine in refluxing DMF or acetonitrile in the presence of a metal fluoride to give aryl halides in low yields. The reactions with chlorinating agents are very sluggish. The reaction of bromine and bis[4-methoxyphenyl] tellurium dichloride formed 2,4-dibromomethoxybenzene in 76% yield. Reactions of these tellurium dichlorides with copper(I) cyanide in DMF produced aryl cyanides in yields of less than 8%3. 

Diaryl tellurium dihalides in toluene solutions reacted with aryl magnesium bromides in diethyl ether to yield triaryl telluronium salts in yields ranging from 6 to 78% (Vol. IX, p. 1082/3)3-5. Aqueous solutions of the products were generally treated with potassium iodide to convert the telluronium halides to telluronium iodides3,4. 

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