Tellurium ethoxide

Weng, L.Q. and Hodgson, S.N.B. (2001) Sol-gel processing of tellurite materials from tellurium ethoxide precursor. 

H-l,3-ditellurole. Under an atmosphere of argon, 0.23 g (2.4 mmol) of trimethylsily-lacetylene are dissolved in 5 mL dry tetrahydrofuran. The solution is cooled to -70°C. n-Butyl lithium (1.0 mL, 2.4 M, 24 mmol) is dropped into the stirred solution. Then 0.20 g (2.0 mmol) of tellurium powder is added. The mixture is warmed to 20°C and kept at this temperature for 2 h. To this mixture, cooled again to -70°C, is added a solution of 0.35 g (2.0 mmol) of chloroiodomethane in 1 mL of tetrahydrofuran. The mixture is stirred for 15 min and then quenched with 50 mL water. The product is extracted with three 15 mL portions of dichloromethane. The combined extracts are washed with brine, dried with anhydrous sodium sulphate and filtered. The filtrate is concentrated to give trimethylsilylethynyl chloromethyl tellurium as a pale-yellow oil. Tellurium powder (0.125 g, 1.0 mmol) is added to 2 mL of a 1 M solution (2.0 mmol) of lithium triethylborohydride in ethanol. The mixture is stirred at 20°C for 2 h under an atmosphere of argon. Then 2 mL of 1 M sodinm ethoxide in ethanol are added followed by 0.27 g (1.0 mmol) of trimethylsilylethynyl chloromethyl tellurium dissolved in 2 mL dimethylformamide. The mixture is stirred for 15 h at 20°C, then diluted with 25 mL water and extracted with three 15 mL portions of dichloromethane. The combined extracts are dried with anhydrons sodinm snlphate, fdtered and the filtrate concentrated. The residue is chromatographed on silica gel with hexane/dichloromethane (1 1) as mobile phase. The fractions containing the prodnct are concentrated and recrystallized from methanol 65% yield, m.p. 85°C. 

Diphenyl telluropyran-4-one (typicalprocedure)7° 120 mL (0.12 mol) of a 1.0 M solution of lithium triethylborohydride in tetrahydrofuran are added to 7.65 g (60 mmol) of powdered tellurium under nitrogen, and the mixture stirred at 20°C for 4 h. A solution of sodium ethoxide (prepared from 5.52 g (0.24 mol) of sodium and 240 mL of absolute alcohol) is added to the dilithium telluride, 13.8 g (60 mmol) of bis(phenylethynyl) ketone are dissolved in a mixture of 150 mL of tetrahydrofuran and 150 mL of 1 M sodium ethoxide in ethanol this solution is poured as quickly as possible into the deep-purple-coloured dilithium telluride soluhon. The flask containing the reaction mixture is immediately placed in a water bath at 50°C and the temperature slowly increased over 30 min until ethanol begins to condense on the side of the flask. The water bath is removed and the mixture is stirred overnight at 20°C. Dichloromethane (400 mL) is then added, the resultant mixture is washed with 800 mL of water, and the organic phase is separated and concentrated to an oil. The oil is dissolved in 600 mL of dichloromethane, and the solution is filtered through a pad of sand. The filtrate is washed with 200 mL of 2% aqueous sodium chloride soluhon, dried with anhydrous sodium sulphate, filtered and evaporated. The brownish solid residue is triturated with 20 mL of butanenitrile and the fine yellow solid is collected by filtration yield 10.9 g (51%) m.p. 126-129°C (from acetonitrile). 

Tellurium Tetraethoxide2 188.3 g (0.5 mol) of diammonium hexachlorotellurate are suspended in 500 ml of absolute ethanol and a cooled solution of sodium ethoxide, prepared by careful addition of 50 g (2.17 mol) of sodium in small pieces to 400 ml of ethanol, is added dropwise. The mixture is healed under reflux until evolution of ammonia has ceased, filtered to remove sodium chloride, and ethanol is distilled from the filtrate. The residue is distilled under vacuum to give the product as a colorless oil b.p. 10770.3 torr. 

Tellurolates were formed when bisfbenzoyl] tellurium compounds were reacted with primary amines, with secondary amines, or with potassium ethoxide in dichloromethane at — 30° under an atmosphere of argon. The tellurolates were oily substances that were too unstable thermally and towards oxygen for purification. They were alkylated to 7e-alkyl tellurolobenzoates or oxidized to ditellurium derivatives3. 

Bis[2-methoxybenzoyl] tellurium reacted with potassium ethoxide, piperidine, morpholine, or aniline to produce potassium or ammonium salts of 2-methoxy-7c-benzoate3. 

Potassium 2-methoxytellurobenzoate was prepared from bis[2-methoxybenzoyl] tellurium and potassium ethoxide in dichloromethane under an atmosphere of argon at — 30°. The ammonium salts were formed similarly by addition of cyclohexylamine, piperidine, or morpholine to diacyl telluriums2. 

Selenium and tellurium alkoxides are also highly volatile and tend to be monomeric. For example, ethoxo-, -butoxo-, and isopropoxo-derivatives of selenium have been volatilized at 76°C/10.0, 110°C77.0, and 88°C/4.5mm pressures, respectively. Similarly tellurium tetramethoxide, ethoxide, -butoxide, and isopropoxide distilled at 115°C/9.0, 107°C/5.0, 150°C/0.8, and 76°C/0.5mm pressure, respectively. 

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