From Arenetellurolates

Arenetellurolates are obtained when tellurium is reacted with aromatic lithium compounds in THF or diethyl ether (p. 154) or with aromatic Grignard reagents in THF. The arenetellurolates thus formed are hydrolyzed to tellurols. The tellurols are oxidized to the diaryl ditellurium products. 

Diphenyl DitelluriumIn a 500 ml argon-purged flask fitted with a reflux condenser, a dropping funnel, a gas inlet tube, and a magnetic stirrer are placed 300 ml of anhydrous tetrahydrofuran and 25.5 g (0.2 mol) of powdered tellurium. 100 m/of 2.0 molar phenyl lithium (0.2 mol) solution in diethyl ether/benzene are added dropwise to the well-stirred tellurium suspension, and the resultant mixture is stirred at 20° for 2 h and under reflux for 1 h. The reaction mixture, which should contain only a small amount of unreacted tellurium, is allowed to cool to 20°, and is poured into 1000 ml of water. Oxygen (or air) is bubbled for 1 h through the mixture which is then extracted with 100 m/ of benzene. The benzene solution is washed three times with water, dried with sodium sulfate, and the benzene is evaporated completely. The residue is recrystallized from ethanol yield 77% m.p. 63.8-65.0°. 

The following diaryl ditellurium compounds were similarly prepared  

Instead of air, potassium hexacyanoferrate(III) can also be used to oxidize tellurols to diaryl ditellurium products. This method produced the following JV-heterocyclic ditellurium compounds from the lithium tellurolates  

Bis[l-naphthyl] Ditellurium To a stirred solution of 0.15 mol of naphthyl lithium in 200 ml of anhydrous diethyl ether under an inert atmosphere are added in small portions 18 g (0.14 mol) of commercial tellurium powder. After completion of the addition, the mixture is stirred and heated under reflux for 30 min and then poured into aqueous 6 molar hydrochloric acid containing ice. This operation most be performed in a well-ventilated hood to avoid exposure to hydrogen telluride. Air is then bubbled through the filtered mixture which is subsequently extracted several times with diethyl ether. The extracts are dried with magnesium sulfate and evaporated. The residue is recrystallized from petroleum ether (b.p. 20 40°) yield 66% m.p. 119 122°. Similarly prepared were the following diaryl ditellurium compounds  

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Tellurols, derivatives of dihydrogen telluride, have received little attention. Only methane-, ethane-, propane-, and butane tellur ol have been isolated from reactions of aluminum telluride with alcohols at 300° or from additions of alkyl bromides to a solution of dihydrogen telluride in absolute ethanol containing sodium ethoxide (s. Vol. IX, 970). No arenetellurol has yet been isolated. 

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. 

Sodium arenetellurolates condensed with aroyl chlorides6 to produce aroyl aryl tellurium derivatives (p. 501). Acetic and propanoic anhydrides reacted similarly7. Butyl aroyl or acyl tellurium compounds were obtained from reactions between lithium (sodium) butanetellurolates and aroyl chlorides6-8, acyl chlorides8, or acetic anhydride9. 

From Silicon, Phosphorus, or Arsenic Alkane- or Arenetellurolates... 

Bis[cyclopentadienyl]bis[arenetellurolato]molybdenum compounds were obtained as quite air-stable, brown solids from bromomagnesium arenetellurolates and bis[cyclopentadien-yl]molybdenum dichloride2. 

Copper(I) alkanetellurolates and arenetellurolates were prepared from the sodium tellurolates or triphenylstannyl organo tellurium compounds and copper(I) chloride. The copper tellurolates are extremely insoluble, polymeric red-brown solids. 

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. 

Arenetellurolates, prepared from diaryl ditellurium compounds via reduction with sodium borohydride in organic media, interact with arenediazonium chlorides2 and arenediazonium tetrafluoroborates3 to produce unsymmetrical diaryl tellurium products in yields below 50%. The arenediazonium chlorides were added as aqueous solutions to the tellurolates. Arenediazonium tetrafluoroborates were used as solids. 

Alkyl phenyl telluriums, obtained from alkyl halides and arenetellurolates, are reduced by triphenyl tin hydride to alkanes under mild conditions1. The alkanes were obtained in yields ranging from 71 to 95%. 5oe-Cholestan-3a-yl phenyl tellurium was similarly reduced to 5 a-cholestane in 89% yield. The reaction appears to be highly chemoselective as indicated by the reduction of an epoxide to an alcohol in the presence of a carbonyl group1. 

Oxidation of the ethylene acetals of 3-aryl-3-oxo-2-propyl phenyl telluriums, which were prepared from the acetals of 3-aryl-3-oxo-2-bromopropane and arenetellurolates, with 3-chloroperoxybenzoic acid in methanol at 20° produced hydroxyethyl 2-arylpropanoates2. Tellurones were postulated as intermediates that experienced a 1,2-aryl shift and the elimination of an aryltelluro moiety. 

Arylselenomethyl aryl telluriums are obtained from sodium arenetellurolates and (arylseleno)bromomethanes. The tellurolates are generated by the reduction of diaryl ditelluriums with sodium borohydride2. 

Bis 4-ethoxyphenyltelluro methme was also isolated as the dibromomethane adduct (m.p. 154°) or as the diiodomethane adduct (m.p. 118°) from reaction mixtures consisting of the arenetellurolate, the dihalomethane and ethanol/benzene/aqueous sodium hydroxide6. Reactions with dichloromethane gave products of indefinite composition6. 

However, when t-butyl lithium was used to generate an aryl lithium compound from an aryl bromide, the /-butyl bromide formed did not react with the lithium arenetellurolate . 

Lithium alkanetellurolates, prepared from tellurium and an alkyl lithium compound or dialkyl ditellurium derivatives and hthium, and sodium arenetellurolates, obtained from diaryl ditellurium compounds and sodium borohydride ", reacted with triorganosilyl, -germyl, -stannyl, and -plumbyl chlorides to produce, for instance, organo triorganosilyl tellurium compounds. 

When aqueous solutions of sodium arenetellurolates and cyclopentadienylbis[tributyl-phosphanejnickel chloride were mixed at 20° under an atmosphere of nitrogen, oils were formed immediately. The oils were extracted with benzene, the extracts dried over anhydrous calcium chloride, and the dried extracts evaporated. The residues were recrystallized from pentane. The complexes were obtained in yields ranging from 76 to 88%. 

Arenetellurolato-/x-cliloropanadiiiin(lI) 0.50 mmol of the diaryl ditellurium are dissolved in ethanol at 20°. A solution of sodium borohydride in ethanol is added until the mixture has turned from red to pale-yellow. A solution of 294 mg (1.0 mmol) of disodium tetrachloropalladate(II) in ethanol is poured into the arenetellurolate solution. The mixture is stirred for 4 h. The dark-brown precipitate is collected by filtration, washed with water, ethanol, and diethyl ether, and dried under vacuum. 

Alkyl organo tellurium compounds, prepared from alkane- or arenetellurolates and alkyl halides, react with butyl lithium,. 9ec-butyl lithium, /ert.-butyl lithium, or phenyl lithium. The alkyl group bonded to the tellurium atom is cleaved from the tellurium and is present in solution as the alkyl lithium that can be used for further reactions. This tellurium-lithium exchange reaction is synthetically useful, whenever the alkyl halides cannot be converted to alkyl lithiums by other, more conventional halogen exchange reactions. The following exchange reactions were successfully carried out ... 

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