Nitrogen Tellurolates

Organosilyl, germyl, and stannyl tellurium derivatives were converted on irradiation with laser light at 488 nm, or on prolonged storage, to diorgano tellurium and bis[silyl, germyl, or stannyl] tellurium derivatives.  

However, methyl silyl tellurium decomposed forming silane and silylene bis[methyltellur-iumY- 

74) Nitrogen, Phosphorus, Arsenic, Antimony, and Bismuth Tellurolates 

The few compounds known that contain a C—Te —M (M = P, As, Sb, Bi) group are oxygen-sensitive and some are light-sensitive. Some of the compounds are stable only at low temperature and decompose at 20°. Water or alcohols do not attack the Te — M bonds. 

Diaryl tellurium arenesulfonimides and diphenyl ditellurium reacted in absolute chloroform at 20°. N,N-Bis[phenyltelluro]arenesulfonamide and the diaryl tellurium were obtained.  

---

These compounds are described in the Section on Nitrogen Tellurolates (s. p. 195)... 

Calcined MCM-41 was dehydrated at 120°C under 10 3 torr for three hours. Different amounts of the copper tellurolate cluster I were then mixed with dehydrated MCM-41. The mixture was mechanically stirred under nitrogen at atmospheric pressure until a yellow homogeneous powder was obtained. TGA, PXRD and IR studies were then carried out. 

Dihydrogen telluride is an acid in aqueous solution and is comparable in strength with phosphoric acid. Tellurols, especially arenetellurols, are expected to be at least as acidic as dihydrogen telluride. Therefore, tellurols should react easily with alkali metal hydroxides to form alkali metal tellurolates. Because tellurols are difficult to prepare, alkali metal tellurolates are best obtained by methods which avoid the tellurols. Sodium and lithium tellurolates are the most frequently used tellurolates. Although the tellurolates are not as sensitive to oxidation as the tellurols, tellurolates are almost always used in situ and are prepared and stored under nitrogen. Sodium benzenetellurolate was isolated as a moisture-and air-sensitive, grey powder. Its solutions in tetrahydrofuran or acetone were found to be stable for months when kept under nitrogen6. 

Sodium Pbenylethynetellurolate5 An apparatus suitable for work with liquid ammonia under a nitrogen atmosphere is set up. A 500-m/flask is charged with 250 ml of liquid ammonia freshly distilled from sodium. In the liquid ammonia are dissolved 1.15 g (0.05 mol) of sodium, a catalytic amount of iron(III) nitrate is added, and 5.1 g (0,05 mol) of phenylacetylenc are added dropwise over 0.5 h to the sodium amide solution. The mixture is allowed to stand for 40 min and then 6.4 g (0.05 mol) of finely powdered tellurium arc added to the sodium acetylide solution. The ammonia is evaporated and the residue of sodium phenylethyne-tellurolate can be dissolved in an appropriate solvent for further reactions. 

Diphenyl ditellurium reacts with sodium in liquid ammonia4- 5 or in hexamethylphosphoric triamide6 at 120° under an atmosphere of nitrogen to produce sodium benzenetellurolate. Potassium benzenetellurolate was prepared from diphenyl ditellurium and potassium in liquid ammonia4. The liquid ammonia solutions of the tellurolates can be used for further reactions. If another solvent is desired, the ammonia can be evaporated and the residue dissolved in the solvent of choice. 

Potassium benzenetellurolate is stable for months under an atmosphere of nitrogen, but decomposes readily in contact with oxygen or moisture. The tellurolate is soluble in liquid ammonia, in acetone, and in tetrahydrofuran. The color of the solution in ammonia is orange1. 

Poly(l,4-phenylene Ditellurium)1 Under nitrogen, a solution of 1 mol of 1,4-dibromobenzene is cooled to — 15° with stirring, a solution of 22 mol of butyl lithium in hexane is added dropwise followed by 1 mol of finely ground tellurium, and the mixture is stirred at 20° until all of the tellurium has dissolved. To this mixture is added 2 mol of butyl lithium followed by 1 mol of powdered tellurium. When all of the tellurium has dissolved, 2 mol of water and then 2 mol of triethylaminc arc added. The resultant tellurolate is oxidized by addition of an aqueous solution of potassium hexacyanoferrate(Ill) yield 54% reddish-brown, amorphous powder. 

The formation of alkylselenocyanates by nucleophilic substitution at the sp carbon atom with potassium selenocyanate (KSeCN) followed by the elimination of hydrogen cyanide or its equivalent has been used for the generation of selenoaldehydes [56,57a,b],selenoketones [57c],and a-acyl selenoamides [58]. Alternatively, the acylation of KSeCN effectively takes place at the nitrogen atom to form acyl selenoisocyanates, that have been trapped with amines [59 a] or tellurols (Eq. 18) [59b]. 

Benzoyl-l-phenyl-l-ethenyI 4-Methoxyphenyl TeUurium A 100-/w/, two-necked flask, fitted with a dropping funnel, a nitrogen inlet tube, and a magnetic stirrer, is charged with a solution of 4.7 g (10 mmol) of bis[4-methoxyphenyl] di tellurium in 10 m/ of absolute ethanol. The apparatus is flushed with nitrogen and 0.84 g (10 mmol) of sodium borohydride are added in small portions to the stirred solution kept at 20°. When the solution has become light yellow, a solution of 3.1 g (15 mmol) of phenyl(benzoyl)ethyne in 10 m/ of ethanol is added over 30 min to the stirred tellurolate solution. The yellow precipitate is filtered off yield 4.9 g (71%) m.p. 151° (from ethanol). 

Methoxyphenyl Phenyl Tellurium (Grignard Method) Phenyl magnesium bromide is prepared from 0.84 g (35 mmol) of magnesium and 5.5 g (35 mmol) of bromobenzene in 15 m/ of absolute diethyl ether under nitrogen and the resultant solution is cooled in an ice/watcr bath. 4.7 g (10 mmol) of bis [4-methoxyphenyl] ditellurium dissolved in 100 ml of absolute diethyl ether are added dropwise to the Grignard solution. Then 250 ml of petroleum ether (b.p. 30- 50°) are added to precipitate the tellurolate and the mixture is allowed to stand for 2 h. The precipitate is filtered off, the filtrate is mixed with aqueous ammonium chloride solution, the organic phase is separated, dried with sodium sulfate, and the solvent is evaporated. Methanol is added to the oily residue to crystallize the product yield 3.1 g (100%) m.p. 61° (from methanol). 

Selenolates such as Na2Se, NaSeH, PhSeNa, etc., and tellurolates such as NapTe, NaTeH, PhTeNa, etc., are excellent nucleophiles and can reduce a variety of functional groups by nucleophilic attack or single electron-transfer. On treatment with alkali metal selenolates (or amine salts of HpSe and PhSeH), reduction or reductive selenation of ketones and aldehydes, C=C reduction of a,/l-unsaturated compounds, and reduction of nitrogen compounds such as nitro compounds occur successfully [118, 176]. Compared with these selenolate anions, the corresponding tellurium compounds are highly reactive not only toward the same substrates but also toward halo compounds such as a-bromo ketones and vic-dibromoalkanes [46, 52, 177]. 

---