Tellurium Diiodide

Diaryl tellurium diiodides afford the iodocyclization of 4-pentenoic acid after 5 and 4 days reflux in CHCI3 in the presence of pyridine. ... 

Typical procedure A solution of 4-pentenoic acid (0.0500 g, 0.500 mmol), bis(p-chlorophenyl)tellurium diiodide (0.302 g, 0.500 mmol) and pyridine (0.040 g, 0.500 mmol) was heated at reflux in 20 mL of chloroform for 5 days. The reaction mixture was concentrated in vacuo, and the residue was purified via chromatography on silica gel eluted with 1 1 hexane/ethyl acetate to give 0.073 g (66%) of the iodolactone and 0.140 mg (80%) of diaryl telluride. 

The third known method of synthesis of the heterocycles 82 is exemplified by the preparation of 4,4-diiodo-l-oxa-4-telluracyclohexane 84 on heating bis(2-iodoethyl)ether with powdered tellurium (45JCS11). It has an analogy in the synthesis of dimethyl tellurium diiodide from methyl iodide and elemental tellurium (20JCS86), but is characterized by a rather low yield (10-13%) of product 84 because of partial decomposition of the initial oxide under the reaction conditions. When bis(2-chloroethyl)ether and Nal were used instead of bis(2-iodoethyl)ether and the reaction was... 

Bis[arylthio] tellurium derivatives reacted with methyl iodide at room temperature forming dimethyl tellurium diiodide and diaryl disulfanes2. 

Excess methyl iodide refluxed with diaryl ditellurium derivatives produced aryl methyl tellurium diiodide and aryl dimethyl telluronium iodides. 

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. 

Bis-[iodomethyl tellurium, the only isolated representative of this class of organic tellurium compounds, was obtained by reduction of bis[iodomethyl] tellurium diiodide with potassium disulfite. The diiodide was prepared in widely fluctuating yields never exceeding 30% by heating amorphous tellurium and diiodomethane at 80° for 49 h1. Bis[iodomethyl] tellurium polymerizes in solution and on heating1. 

When the reaction of benzoyl chloride and tellurium was carried out in the presence of sodium iodide, dibenzoyl tellurium diiodide (m.p. 110°) was isolated in 60% yield. This diiodide was reduced to dibenzoyl tellurium by zinc dust in refluxing chloroform3. 

Bis[4-aminobenzoyl] tellurium dichloride condensed similarly with chloroacetyl chloride to give bis[4-chloroacetylaminobenzoyl] tellurium dichloride (m.p. 140°) in 75% yield2. Dibenzoyl tellurium and dibenzoyl tellurium diiodide condensed with hydroxylamine to give the oximes and with amines to produce Schiff bases3. 

The corresponding derivatives of dibenzoyl tellurium diiodide were obtained in yields between 40 and 60% 1. 

A convenient method to prepare short-chain dialkyl tellurium diiodides uses tellurium and alkyl iodides as starting materials. The neat reagents are heated in a closed tube for several days at temperatures not exceeding 85°. An excess or the stoichiometrically required amount of alkyl iodide may be used. The yield diminishes rapidly with increasing length of the alkyl chain and is only 5% for dipentyl tellurium diiodide1. At temperatures above 80 to 100° the dialkyl tellurium diiodides decompose to the starting materials. 

Iodopropane and 2-iodobutane reacted more rapidly with tellurium than the 1-iodoalkanes. However, the reaction mixtures quickly turned black and only traces of the expected bis[2-alkyl] tellurium diiodides were isolated. 

Alkyl chlorides and bromides can be used as starting materials when sodium iodide is present in the reaction mixture. Dialkyl tellurium diiodides are isolated from these reaction mixtures. 

Tellurium and 1,4-diiodobutane or 1,5-diiodopentane react at 150° to give 1-telluracy-cloalkane 1,1-diiodides9,10. The cyclic tellurium diiodides appear to be thermally more stable than the dialkyl tellurium diiodides5 7,u 12. 

Tellurium tetrachloride and tetraaryl tin compounds reacted under similar conditions to give diphenyl tellurium dichloride (75% yield)2,3 and bis[4-methylphenyl tellurium dichloride (86% yield)4. Tellurium tetraiodide and tetraphenyl tin reacted to give diphenyl tellurium diiodide (m.p. 236°) in only 20% yield1. Tetraethyl tin and tellurium tetrahalides produced reaction mixtures from which the diethyl tellurium dihalides could not be isolated1. 

Diaryl ditellurium compounds refluxed with an excess of methyl iodide are converted to aryl methyl tellurium diiodides. 

Diorgano tellurium compounds are easily converted to diorgano tellurium diiodides upon treatment with elemental iodine. The reactions are carried out with solvents such as benzene, chloroform, carbon tetrachloride, and 1,2-dichloroethane. Because iodine is much less reactive than chlorine or bromine, the reactions can be performed at 20 . The diorganyl tellurium diiodides generally precipitate upon mixing the reagents. 

Dimethyl tellurium diiodide was treated with concentrated ammonia, then with silver nitrate to precipitate silver iodide, and finally with hydrochloric or hydrobromic acid to give dimethyl tellurium dichloride or dibromide4. 

Dimethyl Tellurium Dichloride4 Concentrated ammonia is added to dimethyl tellurium diiodide, and the grey paste that is formed is separated, and dissolved in water. A solution of silver nitrate is added until no more silver iodide precipitates. The silver halide is filtered off, hydrochloric acid is added to the filtrate, and the white precipitate of dimethyl tellurium dichloride is collected m.p. 95°. 

Diphenyl Tellurium Difluoride6 A mixture of 15 ml of dry toluene and 2 g (16 mmol) of silver fluoride is heated to reflux, and 1.3 g (3 mmol) of diphenyl tellurium diiodide are added in portions to the refluxing silver fluoride suspension. Additional diiodide is added after the reddish color of the solution has disappeared. The hot solution is filtered under aspirator vacuum, The filtrate deposits the crystalline product on cooling. The difluoride is filtered off, washed with toluene, and recrystallized from benzene the pure product has m.p. 154°. 

Evaporation of a solution of equimolar amounts of diphenyl tellurium dibromide and mercury(II) chloride in ethanol and extraction of the residue with hot chloroform gave diphenyl tellurium dichloride (m.p. 160°) in high yield. A similar reaction in chloroform converted dimethyl tellurium diiodide to the dichloride (m.p. 90°) in 95% yield3. 

Diorgano tellurium diiodides are most easily converted to diorgano tellurium dibromides by treatment with silver bromide. Ethanol3 or tetrahydrofuran4 served as the reaction medium. 

Benzyl 4-Methoxyphenyl Tellurium Dibromide3 1.16 g (2 mmol) of benzyl 4-methoxyphenyl tellurium diiodide and 1.2 g (4.3 mmol) of silver bromide suspended in 30 m/ of ethanol are stirred at 20° for 1 h. A few drops of40% hydrobromic acid are added. The yellow precipitate is filtered and extracted with cold benzene. Petroleum ether (b.p. 50-70°) is added to the extract to precipitate the dibromide. The dibromide is filtered, dissolved in the minimum volume of hot ethanol, and a few drops of 40% hydrobromic acid are added to the hot ethanol solution. The dibromide crystallizes on cooling as yellow platelets yield 0.75 g (78%) m.p. 153° (dec.). 

Diorgano tellurium dichlorides in ethanol or methanol, when treated with an excess of aqueous iodide at 0 to 5°, produced diorgano tellurium diiodides. Examples of diorgano tellurium diiodides prepared in this manner are ( R given) ... 

The following 2,4-dihydroxyphenyl 4-RO-phenyl tellurium diiodides were obtained similarly in quantitative yields1 ... 

Bis[benzoylmethyl] tellurium diiodide in absolute ethanol was mixed with hydroxylamine hydrochloride. A solution of sodium acetate in ethanol was dropped to the mixture. Heating this mixture for 10 hours produced the dioxime of bis[benzoylmethyl tellurium diiodide3. 

Diorgano tellurium diiodides, but not dibromides and dichlorides, form 1 1 molecular adducts with iodine, iodine monochloride, and iodine monobromide. 

Dimethyl Tellurium Diiodide/lodine Adduct1 A solution of 1.5 g (3.6 mmol) of dimethyl tellurium diiodide in 50 ml of chloroform is mixed with a solution of 1.0 g (4.0 mmol) of iodine in 50 ml of chloroform and the mixture is heated under reflux for 9 min. The mixture is allowed to cool and is then agitated or concentrated to induce crystallization yield 2.4 g (100%) m.p. 89°... 

Dimethyl tellurium diiodide and mercury(II) bromide formed a 1 1 complex in absolute ethanol at 20°8. The same compound was obtained from dimethyl tellurium dibromide and mercury(II) iodide. The corresponding mercury(II) chloride adduct is unstable8. 

Sodium tetraphenylborate converted heterocyclic tellurium diiodides in refluxing ethanol to 7h-phenyl-telluroniacycloalkane tetraphenyl borates5 8. 

Because diaryl tellurium diiodides are not hydrolyzed by boiling water, the diaryl tellurium hydroxide iodides were prepared by treating the hydroxide chlorides or bromides with potassium iodide1. 

Treatment of dialkyl tellurium diiodides with aqueous ammonia, sodium hydroxide, or sodium carbonate is claimed to produce bis[dialkyl tellurium iodide] oxides. 

Dimethyl Tellurium Dimethoxide2 A solution of 4.0 g (60 mmol) of sodium methoxide in methanol is added dropwise to a stirred solution of 12.34 g (30 mmol) of dimethyl tellurium diiodide in the same solvent and the mixture is stirred at 20° for 1 h. The methanol is evaporated under an aspirator vacuum and the residue is distilled under oil pump vacuum to furnish a clear liquid with a garlic-like odor yield 5.9 g (89%) b.p. 60°/l torr. 

Treatment of diphenyl tellurium diacetate with potassium iodide yielded diphenyl tellurium diiodide while the action of trimethylsilyl chloride produced diphenyl tellurium dichloride3. 

Diaryl tellurium arenesulfonimides and excess dry methyl iodide in a sealed tube at 100° produced diaryl tellurium diiodides and /V-methyl arenesulfonamides2. With wet methyl iodide, bis[diphenyl tellurium iodide] oxide was formed2 ... 

From Dimethyl Tellurium Diiodide and Dimethyl Tellurium Dicyanide... 

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