Tellurium Trichlorides

Dialkyl and diaryl ditellurides are easily converted into the corresponding tellurium trichlorides by means of the fission of the Te-Te bond by a chlorinating reagent. This route is very suitable for the preparation of the alkyl derivatives in view of the easy accessibility of dialkyl ditellurides via the alkylation of sodium ditelluride (see Section 3.2.1). 

Chlorobenzotellurophenes were obtained by the thermal cyclization of 2-chloro-2-phenylethenyl tellurium trichlorides. " ... 

Biphenyl tellurium trichloride by heating in nitrobenzene cyclizes to dibenzotel-lurophene dichloride. ... 

Telluroxanthene is prepared from bis(2-lithiophenyl)methane and elemental tellurium or by the cyclization of 2-(phenylmethyl)phenyl tellurium trichloride promoted by AICI3. 

Phenoxatellurium dichlorides are prepared by heating 2-phenoxyphenyl tellurium trichlorides or a mixture of equimolar amounts of TeCl4 and diphenylethers. ... 

Methylphenoxatellurin-lO, 10-dichloride7 2-(4-Methylphenoxy)-phenyl tellurium trichloride (16.8 g, 40 mmol) are heated in a large test tube at 200-240°C in an oil bath for 0.5 h with occasional stirring. The deep red solid is cooled, ground and recrystallized from acetone to give pale yellow plates. Yield 12.2 g (80%), m.p. 275°C. 

The reaction of TeCl4 with siloxycyclopropanes, followed by treatment with DMSO, or bases such TMEDA, EtjN and pyridine, gives a-methylene ketones via the intermediacy of jS-oxoalkyl- or bis(/l-oxoalkyl)tellurium trichlorides or dichlorides. ... 

Six derivatives of this system have been reported. Compound (113) was obtained by successive nitration of 3,4-dimethoxyphenyl tellurium trichloride (112) and partial reduction of the resulting 6-nitro derivative of (112) (Equation (10)). Compounds (47a)-(47c) were obtained by reaction of the oximes (114a)-(114c) with tellurium dioxide (Equation (11)) <86USP4607000,87USP4661438). 

Compounds 13 and 14 are also formed in small amounts in the reactions of tellurium tetrachloride with those 1,3-diketones that afford 11 as the main product. Another by-product of the reaction, when it proceeds in chloroform admixed with ethanol, is the tellurium trichloride 15. A conceivable mechanism for its formation is given by the following sequence of reactions. 

A more general method of preparation of various 10,10-dichlorophen-oxatellurines comprises intramolecular electrophilic cyclization of 2-phenoxyphenyl tellurium trichlorides, which are readily accessible from the corresponding arylmercury chlorides or aryltrimethylsilanes (83MI2). 

The reaction of alkynes with tellurium tetrachloride 16 was recently reinvestigated.68 Aryl alkynes (e.g., 24) react with 16 to give the (Z)-vinylic tellurium trichlorides (e.g., 25) (Equation (5)),47,68,69 whereas alkynes bearing a hydroxyl group at C3 26 give olefins of (ft)-stereochemistry 28 or 29 that reflect the steric demand at C3 (Scheme 7).68,72... 

The purified bis[9-e>-carboranyl] ditellurium was reacted in dichloromethane with the stoichiometrically required amount of thionyl chloride to produce the 9-o-carboranyl tellurium trichloride and with bromine to give the corresponding tellurium tribromide. The tellurium trichloride was reduced with an excess of hydrazine hydrate in ethanol to bis[9-o-... 

Interaction ofocarborane or m-carborane with tellurium tetrachloride in dichloromethane in the presence of aluminum trichloride formed the 9-carboranyl tellurium trichlorides. These compounds were not isolated but reduced by sodium sulfide in aqueous ethanol to the corresponding dicarboranyl ditellurium derivatives, which in turn were reacted with thionyl chloride in ethanol or bromine in dichloromethane to give 9-carboranyl tellurium trihalidcs2 (see p. 5). 

When tellurium tetrachloride was condensed with A,A,jV -tris[trimethylsilyl]benzamidine in dry dichloromethane, N,N -bis[trimethylsilyl benzamidinyl tellurium trichloride was isolated in the form of white crystals that were characterized by single-crystal X-ray diffraction3. The tellurium atom is surrounded by three chlorine and two nitrogen atoms in the monomeric molecule. 

A similar condensation between tellurium tetrachloride and Ar-trimethylsilvl(triphenyl) phosphane imide in toluene yielded triphenylphosphane imidyl tellurium trichloride as yellow crystals that were recrystallized from acetonitrile. In the solid state the molecule is dimeric containing a four-membered Te2N2 cycle with alternating short and long Te-N bonds1. 

Fluoroalkoxy Tellurium Trichlorides2 A mixture of 3 mmol of tellurium tetrakisffluoroalkoxide] and 9 mmol of tellurium tetrachloride is refluxed in 20 ml of tetrahydrofuran for 3 h. The solvent is evaporated and the residue kept at 40 to 5070.03 torr for 2 h. The fluoroalkoxy tellurium trichlorides are isolated as the mono-lelrahydrofuran adducts that are stable below 50". 

Aryl tellurium trichlorides treated with potassium 4-methylbenzenethiosulfonate in boiling methanol formed aryl 4-methylphenylthiosulfonato tellurium derivatives2. 

Methylphenylthiosnlfooato Phenyl Tellurium2 Phenyl tellurium trichloride is dissolved in dry ethyl acetate, 3 molar equivalents of potassium 4-methylbenzenethiosulfonate dissolved in methanol are added, and the mixture is heated under reflux. The hot mixture is filtered, the filtrate is concentrated lo a volume of 5 to 10 m/, and cooled. The orange crystals are collected, recrystallized from methanol, dried, and stored under nitrogen m.p. 138°. 

Phenylazophenyl Tellurium Chloride3 3.5 g (8.4 mmol) of 2-phenylazophenyl tellurium trichloride are dissolved in 50 ml of refluxing methanol. A solution of 0.5 g (10 mmol) of hydrazine hydrate in 50 ml of... 

When the thiosemicarbazones of benzaldehyde, 2-hydroxybenzaldehyde, methyl phenyl ketone, or methyl 2-hydroxyphenyl ketone were reacted with aryl tellurium trichlorides, reduction to the aryl tellurium chlorides occurred. The aryl tellurium chlorides were stabilized by coordination to excess thiosemicarbazone2. 

Phenyl Bis[henzaldehyde thiosemicaihazone] Tellurium Chloride2 A solution of 1.0 g (3.2 mmol) phenyl tellurium trichloride in 30 ml methanol is added to a solution of 2.3 g (12.8 mmol) benzaldehyde thiosemicarbazone in 30 ml of warm water. The mixture is stirred for 0.5 h and then set aside for 12 h. The yellow crystals of the product arc filtered and recrystallized from methanol yield 79% m.p. 70- 72°. 

A 4 1 molar ratio of thiosemicarbazone/aryl tellurium trichloride is necessary for the success of these reactions. No product was obtained with a 2 1 molar ratio of the reactants. The l,3-diphenyl-3-oxo-l-propen-1-yl tellurium trihalides were quantitatively reduced to the corresponding tellurium halides by hypophosphorous acid3. 

Aryl tellurium chlorides, generated from diaryl ditelluriums and chlorine and used in situ, reacted with A.iV-dichloroarenesulfonamides. Aryl tellurium trichlorides and aryl (chloro)tellurium arenesulfonimides were obtained9. 

The reduction of alkyl tellurium trihalides is a convenient method for the preparation of the corresponding dialkyl ditellurium when the trihalides can be obtained by reactions other than the halogenolysis of the dialkyl ditellurium. Addition of tellurium tetrachloride to olefins and condensation with ketones produces alkyl tellurium trichlorides. Sodium sulfide nonahydrate4 and sodium or potassium disulfite5 8 were used as reducing agents. 

Bis[carboxymethyl] Ditellurium5,6 Carboxymethyl tellurium trichloride is suspended in water, a six-fold molar excess of potassium disulfite is added, and the mixture is stirred until evolution of sulfur dioxide has ceased. The mixture is extracted with diethyl ether, solvent is removed from the extract, and the residue is recrystallized from acetone yield 100% m.p. 142° (dec.). 

When 3-chloro-2-(A -benzoyl-7V-phenylamino)-propyl tellurium trichloride was reduced with aqueous sodium disulfite, bis[3-benzoyloxy-2-phenylaminopropyl] ditellurium (m.p. 106°) was isolated in 90% yield. The benzoyl group had migrated during the reduction and had replaced the chlorine atom3. 

Alkoxyalkyl tellurium trichlorides, generated by the reaction of tellurium dioxide in alcoholic aqueous hydrochloric acid, were reduced, without isolation, to the corresponding bis[2-alkoxyalkyl] ditelluriums4. 

Bis[2-benzoyloxy-3-chloropropyl] Ditellurium1 In a 250 ml separatory funnel are placed 0.80 g (1.85 mmol) of 2-benzoyloxy-3-chloropropyl tellurium trichloride, 40 ml of dichloromethane, and 30 ml of 20% (w/v) aqueous sodium sulfide nonahydrate solution. The mixture is shaken until all solids have dissolved, the organic layer is separated, dried, and the solvent evaporated. The product is purified by passing it through a short column of silica with dichloromethane as the mobile phase. The orange-red colored fractions are evaporated to leave a red oil yield 0.48 g (80%). 

Chloroalkyl tellurium trichlorides are generally not reduced to ditellurium derivatives by aqueous sodium sulfide. /l /i-elimination of chloride and the trichlorotelluro group forms olefins3,4. 2-Chloro-2-phenylethenyl tellurium trichloride decomposed to elemental tellurium upon treatment with sodium sulfide nonahydrate2. 

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