TeUurium with

Lead Alloys. A teUurium—lead aUoy containing 0.02—0.1% teUurium, with or without antimony, was introduced in 1934 (81) as teUurium lead or Teledium. This aUoy has higher recrysta11i2ation temperatures and corrosion resistance and takes a significantly longer time to soften at 25°C after cold work. 

Complexes of group VIB elements with sulfur or selenium donor atoms are mainly concerned with complexes of selenium(II), tellurium(II) and tellurium(rV). The structural chemistry of complexes of selenium and teUurium with sulfur- and selenium-containing ligands has been well reviewed in the recent past. ... 

Selenophene and tellurophene were obtained in 15-20% yield by the reaction of selenium and teUurium with diacetylene in the K0H/DMS0/N2H4-H20/H20 system at 0-20°C (90MI1). 

Halogen fluorides react with sulfur, selenium, teUurium, phosphoms, sHicon, and boron at room temperature to form the corresponding fluorides. Slight warming may be needed to initiate the reactions (4) which, once started, proceed rapidly to completion accompanied by heat and light. The lack of protective film formation aHows complete reaction. 

Cold-roUed alloys of lead with 0.06 wt % teUurium often attain ultimate tensile strengths of 25—30 MPa (3625—5350 psi). High mechanical strength, excellent creep resistance, and low levels of alloying elements have made lead—teUurium aUoys the primary material for nuclear shielding for smaU reactors such as those aboard submarines. The aUoy is self-supporting and does not generate secondary radiation. 

Dilution with water reverses the reaction, and heating the solution Hberates sulfur dioxide. Upon being added to a solution of teUurides, teUurium forms colored polyteUurides. Unlike selenium, teUurium is not soluble in aqueous sodium sulfite. This difference offers a method of separating the two elements. Like selenium, teUurium is soluble in hot alkaline solutions except for ammonium hydroxide solutions. Cooling reverses the reaction. Because teUurium forms solutions of anions, Te , and cations, Te" ", teUurium films can be deposited on inert electrodes of either sign. 

Although this procedure yields tellurium as the same compound found in the original feedstock, the copper teUuride is recovered in a comparatively pure state which is readily amenable to processing to commercial elemental tellurium or tellurium dioxide. The upgraded copper teUuride is leached with caustic soda and air to produce a sodium teUurite solution. The sodium teUurite solution can be used as the feed for the production of commercial grade teUurium metal or teUurium dioxide. 

Alternatively, if teUurium dioxide is the product desired, the sodium teUurite solution can be neutralized in a controUed fashion with sulfuric acid. As the pH is lowered, precipitates containing impurities such as lead and sUica that form ate filtered off. At pH 5.6 the solubUity of teUurous acid teaches a minimum and essentiaUy aU of the teUurium precipitates (>98%). After filtration and drying, commercial teUurium dioxide is obtained. A diagram for the process of deteUurizing of slimes and recovering teUurium products is shown in Figure 1. 

Metal teUurides for semiconductors are made by direct melting, melting with excess teUurium and volatilizing the excess under reduced pressure, passing teUurium vapor in an inert gas carrier over a heated metal, and high temperature reduction of oxy compounds with hydrogen or ammonia. 

Although gravimetric methods have been used traditionally for the determination of large amounts of tellurium, more accurate and convenient volumetric methods are favored. The oxidation of teUurium(IV) by ceric sulfate in hot sulfuric acid solution in the presence of chromic ion as catalyst affords a convenient volumetric method for the determination of tellurium (32). Selenium(IV) does not interfere if the sulfuric acid is less than 2 N in concentration. Excess ceric sulfate is added, the excess being titrated with ferrous ammonium sulfate using o-phenanthroline ferrous—sulfate as indicator. The ceric sulfate method is best appHed in tellurium-rich materials such as refined tellurium or tellurium compounds. 

The oxidation of teUurium(IV) by permanganate as an analytical method has been studied in some detail (26). The sample is dissolved in 1 1 nitric-sulfuric acid mixture addition of potassium bisulfate and repeated fuming with sulfuric acid volatilises the selenium. The tellurite is dissolved in 10 vol % sulfuric acid, followed by threefold dilution with water and titration with potassium permanganate ... 

Elemental tellurium and the stable teUurides of heavy nonferrous metals are relatively inert and do not represent a significant health hazard (43—47). Other, more reactive teUurides, including soluble and volatile teUurium compounds such as hydrogen teUuride [7783-09-7] teUurium hexafluoride [7783-80-4] and alkyl teUurides, should be handled with caution. Some of these materials can enter the body by absorption through the skin or by inhalation and ingestion of dust or fumes. No serious consequences or deaths have been reported in workers exposed to teUurium and its compounds in industry (48). 

The unusual physical complaints and findings in workers overexposed to teUurium include somnolence, anorexia, nausea, perspiration, a metallic taste in the mouth and garlic-like odor on the breath (48). The unpleasant odor, attributed to the formation of dimethyl teUuride, has not been associated with any adverse health symptoms. Tellurium compounds and metaboUc products have been identified in exhaled breath, sweat, urine, and feces. Elimination is relatively slow and continuous exposure may result in some accumulation. No definite pathological effects have been observed beyond the physical complaints outlined. Unlike selenium, teUurium has not been proved to be an essential biological trace element. 

Tellurium Sulfide. In the hquid state, teUurium is completely miscible with sulfur. The Te—S phase diagram shows a eutectic at 105—110°C when the sulfur content is 98—99 atom % (94—98 wt %). TeUurium—sulfur aUoys have semiconductor properties (see Semiconductors). Bands attributed to teUurium sulfide [16608-21 -2] TeS, molecules have been observed. 

Tellurium Nitride. TeUurium nitride [12164-01 -0] Te N is an unstable, citron-yeUow soHd that detonates easUy when heated or stmck, but it can be kept under dry chloroform. It is said to explode on contact with water, possibly because of the heat of wetting. 

Copper—lead—teUurium aUoys have high wear resistance in sliding contacts. In copper—2inc aUoys, the benefits of teUurium decrease with increasing 2inc content and almost disappear when the 2inc content exceeds 35%. 

Adding teUurium to lead and to lead aUoyed with sUver and arsenic improves the creep strength and the charging capacity of storage battery electrodes (see Batteries). These aUoys have also been suggested for use as insoluble anodes in electrowinning. 

Betts Electrolytic Process. The Betts process starts with lead bullion, which may carry tin, silver, gold, bismuth, copper, antimony, arsenic, selenium, teUurium, and other impurities, but should contain at least 90% lead (6,7). If more than 0.01% tin is present, it is usually removed from the bullion first by means of a tin-drossing operation (see Tin AND TIN ALLOYS, detinning). The lead bullion is cast as plates or anodes, and numerous anodes are set in parallel in each electrolytic ceU. Between the anodes, thin sheets of pure lead are hung from conductor bars to form the cathodes. Several ceUs are connected in series. 

By-Product Recovery. The anode slime contains gold, silver, platinum, palladium, selenium, and teUurium. The sulfur, selenium, and teUurium in the slimes combine with copper and sUver to give precipitates (30). Some arsenic, antimony, and bismuth can also enter the slime, depending on the concentrations in the electrolyte. Other elements that may precipitate in the electrolytic ceUs are lead and tin, which form lead sulfate and Sn(0H)2S04. 

The mud or slime is coUected from the bottom of the electrolytic ceUs and pumped to the sUver refinery, where it is processed for recovery of copper, precious metals, selenium, and, in many cases, teUurium. The anode slime contains 2—20% selenium as copper and sUver selenides, whereas gold exists as the metal and in combination with teUurium. A flow diagram is shown in Figure 8. 

In contrast to tin-lithium exchange, doubly hthiated bis(hthiomethyl)silanes 117a and 101 with methyl or phenyl substituents at the silicon centre are accessible from bis(teUurio-methyl)silanes 116a,b by a two-fold teUurium-lithium exchange (Scheme 42) . 

TeUurium (0-Ethyl dithiocarbonate) Halides (Halogen Method)1 2.0 g (5 4 mmol) of tellurium bis[0-ethyl dithiocarbonate] are dissolved in 50 ml of dichloromethane, 2.7 mmol of halogen (0.19 g of chlorine, 0.43 g of bromine, or 0.69 g of iodine) dissolved in carbon tetrachloride are added, the mixture is stirred for 1 h, and then filtered. The filtrate is evaporated under reduced pressure, the residue is washed with boiling light petroleum ether, and recrystallized from chloroform/light petroleum ether yield not reported m.p. not reported. 

TeUurium Bislmethanethiosulfonatc]1 4.0 g (25 mmol) of tellurium dioxide are added to a mixture of 15 ml of concentrated hydrochloric acid and 5 ml of water, the solution is stirred and cooled in an ice/water bath. A solution of 15 g (112 mmol) of sodium methanethiosulfonate in 15 m/ of water is added dropwisc, the resultant mixture is stirred, and the semisolid that separates is agitated with a glass rod until a yellow solid is obtained. The mixture is filtered, the solid is washed with 10 ml of 6 molar hydrochloric acid, three 10 ml portions of methanol, three 10 m/ portions of diethyl ether, five 20 ml portions of warm chloroform, and finally with diethyl ether. The solid is dried under reduced pressure over sulfuric acid, dissolved in boiling chloroform (100-150 m//g), and the solution is filtered. The filtrate is concentrated to half its volume, cooled, the deposited crystals are collected, washed with diethyl ether, and dried under reduced pressure over sulfuric acid crude yield 5 g (57%), m.p. 135° (blackens above 120°). 

TeUurium Bis[benzenethiosulfonate]2 5.4 g (20 mmol) of tellurium tetrachloride are suspended in 30 ml of ethanol-free chloroform, the suspension is stirred with ice cooling, and 20 g (94 mmol) of potassium benzene thiosulfonate are added in portions. After completion of the addition, the mixture is stirred with cooling for 10 min, the cold yellow suspension is filtered, and the filtrate is discarded. The solid on the filter is treated with two 10 m/portions of ice-cold chloroform and with 10 ml of diethyl ether, the solid is dried under reduced pressure over sulfuric acid, treated with three 30 ml portions of water, two 5 ml portions of diethyl ether, and dried again. This crude product (8 g) is dissolved in 80 ml of boiling chloroform, the mixture is filtered, the filtrate is concentrated to half its volume, and the concentrate is cooled in an ice bath with stirring. The crystals are collected and can be further purified by recrystallization from boiling chloroform (25 ml/2 g) crude yield 8 g (84%) m.p. 170° (dec.). 

Benzenctellurolatobis[diphenyl teUurium]rhodium Dicbloride3 A solution of 2.0 g (7.6 mmol) of rhodium trichloride trihydrate in 120ml of hot ethanol is added to a refluxing solution of 7.75 g (27.5 mmol) of diphenyl tellurium in 250 ml of ethanol, refluxing is continued for 5 min, and 20 ml of 37% aqueous formaldehyde are added. The mixture is heated under reflux for 24 h, cooled to 0°, and filtered. The red solid is washed with hexane and dried yield 5.25 g (73%) dec. 149°. 

Dibutyl TeUurium (Hydrazine Method)1 To a stirred mixture of 0.40 g (10 mmol) powdered sodium hydroxide, 0.64 g (5.0 mmol) of finely ground tellurium powder, and 10 m/ dimethylformamide are added, dropwise by syringe under an atmosphere of nitrogen at 50- 60° 0.50 ml (7.1 mmol) 80% hydrazine hydrate. The mixture is stirred for 3 h. A solution of 1.4 g (10 mmol) bromobutane in 2 ml dimethylformamide is added and the mixture heated at 60° for 30 min, then cooled to 20°, and extracted with petroleum ether (30 -60°). The organic phase is separated, washed with water, and dried with anhydrous calcium chloride. The mixture is filtered and the solvent evaporated from the filtrate. The residue is purified by preparative TLC (silica gel, Merck 60 GF 254/hexane) yield 57% b.p. 111-114713 torr. 

Tokitoh, Okazaki and coworkers have reported that when the stable diarylgermylene 117, obtained by reduction of the corresponding dibromide with lithium naphthalenide, was allowed to react with an equimolar amount of elemental teUurium in THF, a germanetellone 118 was obtained directly (Scheme 45). ... 

Diethyl TeUurium (Liquid Ammonia Method) An apparatus suitable for work with liquid ammonia is set up. 12.7 g (0.1 mol) of fine tellurium powder are suspended in liquid ammonia and then 4.6 g (0.2 mol) of sodium are added to the suspension. The mixture is stirred for 4 h. 10.9 g (0.1 mol) of ethyl bromide are added dropwise to the liquid ammonia, and the mixture is stirred for 30 min. The ammonia is evaporated. Water is added to the residue, the aqueous solution is extracted with diethyl ether, and the extract is dried with magnesium sulfate. The ether is evaporated and the residual liquid is distilled yield 7 g (38%) b.p. 138 . 

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). 

Bis[4-bydroxybenzoyl] TeUurium DicUoride (Demethylation Method) 0.47 g (1 mmol) of bis[4-methoxybenzoyl] tellurium dichloride are dissolved in 50 ml of dry benzene and 0.4 g (3 mmol) of aluminum trichloride are added. The mixture is heated under reflux on a water bath for 30 h, then poured onto crushed ice, and allowed to warm to 20°. The resultant mixture is extracted repeatedly with chloroform, the combined extracts are dried with anhydrous sodium sulfate, filtered, and the filtrate concentrated. The residue is recrystallized from petroleum ether. 

Bis[4-meth) lphenyl] TeUurium Dibntanoate" In a 100 ml flask fitted with a reflux condenser and a magnetic stirrer are placed 0.76 g (2 mmol) of bis[4-methylphenyl] tellurium dichloride, 0.35 g (4 mmol) of butanoic acid, 0.47 g (2 mmol) of silver oxide, and 30 ml of benzene. The mixture is heated under reflux with stirring for 4 h, filtered, and the filtrate is evaporated. The residue is recrystallized from petroleum ether yield 0.87 g (90%) m.p. 127°. 

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