Telluronium Iodide

Fig. 9 Interconversion of enantiomers of A, A -dimethyl-2-(aminomethyl)phenyl iodo-telluronium iodide (18) and A, A -dimethyl-2-(aminomethyl)phenyl bromotelluronium bromide (19).

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

The following aryl methyl tellurium compounds were prepared from the aryl dimethyl telluronium iodides in refluxing pyridine. 

Formylphenyl Methyl Tellurium1 20 g (0.05 mol) of 2-formylphenyl dimethyl telluronium iodide are dissolved in 100 m/of pyridine and the solution is heated under reflux for 3 h. The solution is then cooled and poured into a mixture of ice and dilute hydrochloric acid. The mixture is extracted with diethyl ether, the extract is washed with water, dried with magnesium sulfate, the solvent is distilled off, and the residue is fractionally distilled under vacuum yield 9.8 g (77%) b.p. 120 13070.1 torr (13.3 Pa). 

Similar reactions starting with the ethylene acetals of 3-formyl- or 3-acetyl-2-thienyl dimethyl telluronium iodides yielded 3-formyl- or 3-acetyl-2-thienyl methyl tellurium. The acetals were hydrolyzed before the products were isolated2. 

Ethoxyphenyl Methyl Tellurium Diiodide1 A mixture of 1 g (1.98 mmol) of bis[ethoxyphenyl] ditcllurium and 50 g (0.35 mol) of methyl iodide is heated under reflux for 0.5 h. The yellow precipitate of dimethyl 4-ethoxyphenyl telluronium iodide is filtered off. Light petroleum ether is added to the cold filtrate to crystallize the product yield 0.34 g (33%) m.p. 108°. 

Cathodic reduction of tellurium in the presence of methyl iodide in a 1.0 M solution of sodium perchlorate in anhydrous dimethylformamide produced trimethyl telluronium iodide in 80% yield1. This reaction does not appear to proceed with other alkyl halides. 

IHmethyl Telluronium Iodide2 250 ml of a 0.48 molar solution of methyl lithium (120 mmol) in diethyl ether are cooled under an inert atmosphere to — 70° and a solution of 7.8 g(29 mmol) of tellurium tetrachloride in 100 ml of diethyl ether is added dropwise with stirring. On completion of the addition, the mixture is allowed to warm to 20° and to stand at 20° for 30 min. It is then hydrolyzed with ice/water, and the aqueous phase is separated and added to a saturated aqueous solution of sodium iodide. Precipitated trimethyl telluronium iodide is collected and recrystallized from water yield 1.7 g (84%) sublimes between 213 and 257°... 

The following aryl dimethyl telluronium iodides were similarly prepared ... 

When refluxed in excess methyl iodide, diaryl ditellurium compounds produced aryl dimethyl telluronium iodides as one of the products3,4 (Vol. IX, p. 1078). 

Similarly prepared were the following alkynyl dimethyl telluronium iodides ... 

The following dimethyl 2-R-phenyl telluronium iodides were prepared from the methyl aryl telluriums and methyl iodide in nitromethane at 60°6. 

Divinyl tellurium reacted with alkyl iodides in ethanol at 20° to yield alkyl divinyl telluronium iodides. The reaction time increased with increasing chain length of the alkyl iodide from 4 h for methyl iodide to six days for butyl iodide2,3. 

Dibutyl Methyl Telluronium Iodide2 95 mg (0.19 mmol) of dibutyl tellurium diiodidc, 20 ml of methyl iodide, 35 mg (0.22 mmol) of potassium sulfite, 24 mg (0.22 mmol) of sodium carbonate, and 5 ml of water are placed in a conical flask. The mixture is shaken vigorously, kept at 20° for 3 days, filtered, the filtrate is evaporated to dryness, and the residue is recrystallized from water yield 45 mg (62%) m.p. 157°. Similarly prepared were the following telluronium iodides ... 

Dimethyl tellurium, however, reacted with phenyl iodide at 20° to produce dimethyl phenyl telluronium iodide in 50% yield4. 

Diphenyl Naphthyl Telluronium Iodide1 10 g (28 mmol) of diphenyl tellurium dichloridc are dissolved in 250 ml of dry toluene. A solution of 1 -naphthyl magnesium bromide in diethyl ether is prepared from 17.4 g (84 mmol) of 1-bromonaphthalene. The solution of the tellurium compound is quickly poured into the freshly prepared Grignard solution, the mixture is shaken vigorously, and 20 ml of dilute hydrochloric acid are added immediately. The solution is decanted from the precipitate, the precipitate is dissolved in boiling water, silver chloride is added, and the mixture is heated. The mixture is then filtered, sodium sulfite is added to the filtrate, and the telluronium iodide is precipitated by the addition of potassium iodide yield 11.8 g (78%) m.p. 148° (from ethanol, ethanol/diethyl ether). 

Trimethyl telluronium iodide and iodine combined to give purple trimethyl telluronium triiodide (m.p. 76°, from ethyl acetate)5. 

Triorgano telluronium iodides crystallize easily, whereas the chlorides are often obtained as oils or tars4. 

Aqueous or methanolic solutions of triorgano telluronium bromides that are not too dilute precipitate triorgano telluronium iodides when mixed with solutions of potassium iodide5,6 (Vol. IX, p. 1080). 

The solubility difference between silver iodide and silver bromide was exploited to convert triorgano telluronium iodides to bromides in reactions with silver bromide7-11. 

Tris[4-methylphenyl] Telluronium Bromide1 2.0 g (3.5 mmol) of tris[4-methylphenyl] telluronium iodide are dissolvedin 10 ml of methanol, 400 ml of water are added to form a milky suspension, excess silver bromide is added, and the mixture is stirred and heated under reflux for 0.5 h. The hot mixture is filtered, the filtrate is cooled, filtered, and the solid is recrystallized from water m.p. 266° (dec.). 

Boiling solutions or suspensions of triorgano telluronium iodides in water or ethanol with an excess of silver chloride produces triorgano telluronium chlorides. Some of the telluronium chlorides were obtained only as oils or tars7. 

Trimethyl Telluronium Picrate1 Trimethyl telluronium iodide, prepared from 1.6 g of dimethyl tellurium diiodide, potassium sulfite, and methyl iodide, is dissolved in water and a saturated aqueous solution of picric acid is added until precipitation of the telluronium picrate ceases. The solid is filtered off, washed with cold water, and dried in air yield 0.3 g (20% based on dimethyl tellurium diiodide) m.p. 127° (dec.). 

Diphenyl Methyl Telluronium Benzoate8 1.0 g (2 mmol) of diphenyl methyl telluronium iodide and 0.46 g (2 mmol) of silver benzoate in 50 ml of distilled water are stirred at 20° for 0.5 h and then heated under reflux for 4 h. Silver iodide is filtered off, the filtrate is concentrated under vacuum at 20°, and the precipitate is filtered off and dried over phosphorus pentoxide m.p. 105". 

Diphenyl Methyl Telluronium Tetrafluoroborate4 0.5 g (1.2 mmol) of diphenyl methyl telluronium iodide are dissolved in water. An aqueous solution containing 0.23 g (1.2 mmol) of silver tetrafluoroborate is prepared by reacting equivalent amounts of silver oxide and tetrafluoro boric acid. The solutions are mixed, stirred for 1 h at 20°, heated under reflux for 4 h, and concentrated. Silver iodide is filtered off and the product crystallized m.p. 135°. 

Bis[2-methylphenyl ] Methyl Telluronium Nitrate6 An aqueous solution of bis[2-methylphenyl] methyl telluronium iodide containing aslight excess of silver nitrate is boiled. Silver iodide is filtered off, the filtrate is concentrated (if necessary), the precipitate is collected, and dried m.p. 157°. 

Diphenyl Methyl Telluronium Hexaflnorophosphate8 30 g of IRA 400 resin are converted to the hexafluorophosphate form and added to 200 ml of water containing 0.2 g (0.5 mmol) of diphenyl methyl telluronium iodide. The mixture is stirred and warmed gently for 4 h, filtered, and the filtrate concentrated to give the colourless crystalline product m.p. 135°. 

Acetals of 2-formyl- or acetylphenyl dimethyl telluronium iodides were hydrolyzed in acidic medium to 2-formyl- or acetylphenyl dimethyl telluronium iodides3. 

Dimethyl 2-Formylphenyl Telluronium Iodide3 10 g (2.1 mmol) of 2-(diethoxymethyl)phenyl dimethyl telluronium iodide are added to 100 ml of 4 molar hydrochloric acid, the mixture is heated with stirring for 2 h, cooled, and the solid is filtered off yield 7.4 g (90%) m.p. 125-130° (from glacial acetic acid or methanol). 

Similarly prepared were 2-acetylphenyl dimethyl telluronium iodide (90% yield m.p. 145-150°) and 4-acetylphenyl dimethyl telluronium iodide (80% yield m.p. 151-154°) from the corresponding dimethylene acetals4. 

Of preparative importance is the conversion of aryl alkyl methyl telluronium iodides to aryl alkyl telluriums7-9 (see p.439). 

Bis[2,2 -biphenyldiyl] TeDiirium3 A solution of 6.92 mmol of 2,2 -dilithiobiphenyl in 100 m/of diethyl ether is prepared under nitrogen and 1.46 g (3.46 mmol) of 2,2 -biphenyldiyl methyl telluronium iodide are added. The mixture is stirred at 20° overnight and the crystalline product is filtered under nitrogen yield 0.78 g... 

The reaction between 2,2 -biphenyldiyl 2-iodo-2 -biphcnyl telluronium iodide and phenyl lithium produced bis[2,2 -biphenyldiyl] tellurium2. 

Tetraphenyl tellurium was similarly obtained in 34% yield from triphenyl telluronium iodide and phenyl lithium1,5. Solutions of tetramethyl tellurium were prepared from trimethyl telluronium iodide and methyl lithium3. The formation of butyl triphenyl tellurium was claimed in a reaction of triphenyl telluronium iodide and butyl lithium4. Equimolar amounts of triphenyl telluronium chloride and 3,3-bis[chloromercuro]-2,4-pentadione in refluxing methanol produced 3-[chloromercuro]-2,4-dioxopent-3-yl triphenyl tellurium6. 

Tetrabutyl tellurium and bis[2,2 -biphenyldiyl] arsonium or phosphonium iodide formed tributyl telluronium iodide and butyl bis[2,2 -biphenyldiyl] arsenic or phosphorus1. 

The reaction of trimethyl telluronium iodide with 2,2 -dilithiobiphenyl produced dibenzotellurophene in 37% yield1. 

Benzotellurin and methyl iodide produce the telluronium iodide in an exothermic reaction. When the reaction is carried out in the presence of silver perchlorate, the telluronium perchlorate is isolated3. 

---