Tellurium chlorides

Metal Coatings. Tellurium chlorides, as well as tellurium dioxide in hydrochloric acid solution, impart permanent and attractive black antique finish to silverware, aluminum, and brass. Anodized aluminum is colored dark gold by tellurium electro deposition. A solution containing sodium tellurate and copper ions forms a black or blue-black coating on ferrous and nonferrous metals and alloys. Addition of sodium tellurite improves the corrosion resistance of electroplated nickel. Tellurium diethyldithiocarbamate is an additive in bright copper electroplating (see Electroplating). 

INVERSION, ALKENES Tellurium chloride. Trifluoroacetyl chloride. 

Hydrogen telluride is very sensitive towards the halogen elements. It not only readily reduces chlorine, bromine and iodine to the corresponding hydracids with simultaneous liberation of tellurium (which in the case of chlorine can further pass easily into the tetrachloride), but it also reduces solutions of such salts as ferric chloride and mercuric chloride to the lower chlorides, tellurium being precipitated. It also reduces tellurium chlorides, the only products being hydrogen chloride and tellurium. 

Diethyl telluride, (C2H5)2Te,3 results when a sodium or potassium alloy of tellurium is distilled with an aqueous solution of barium ethyl sulphate. It is a yellowish-red heavy liquid, B.pt. 100° C. It also occurs when triethyl tellurium chloride reacts with zinc diethyl at 100° to 110° C., butane being obtained as a by-product 4 prepared by this method the boiling-point is given as 140° C. It readily inflames, burning with a bright blue flame, and oxidises in direct sunlight. 

Triethyl tellurium chloride,2 (CgHg TeCl, is isolated when an ether solution of tellurium tetrachloride is added dropwise to a similar solution of zinc diethyl. It crystallises from alcohol as colourless plates, M.pt. 174° C., readily soluble in alcohol, sparingly soluble in ether. It is deliquescent in air, and with moist silver oxide gives a hydroxide. 

Di-o-tolyl methyl tellurium chloride,2 (C7H7)2(CH3)TeCl, is obtained by boiling the corresponding iodide with silver chloride and water. It separates from water as four-sided plates containing two molecules of water of crystallisation, melting at 93° C. and again at 148° C. from chloroform it crystallises with half a molecule of chloroform, and melts at 155° to 156° C. The basic zinc chloride double salt melts with decomposition at 186° to 187° C. 

Tri-p-tolyl tellurium iodide1 melts with decomposition at 232° to 233° C., dissolves readily in methyl alcohol or chloroform, less readily in benzene or ether, and is insoluble in water. Tri-p-tolyl tellurium bromide occurs when the iodide or chloride is boiled with silver bromide. It melts at 265° to 266° C. with decomposition, and dissolves in alcohols or chloroform, but is insoluble in benzene or ether. Tri-p-tolyl tellurium chloride is prepared from the bromide in the usual way. It melts at 260° to 261° C. and gives precipitates with the chlorides of mercury, tin and gold, picric acid and platinic chloride. The hydroxide is a resin, melting at about 110° C., and yielding a pier ate, consisting of long prisms, M.pt. 194° to 195° C.a... 

General Procedure.—The basic tellurium chloride suspended in three times its weight of dry ether is treated with an excess of the cresol (2 to 4 mols.), the solvent distilled off and the residue heated at 120° to 130° C. in the case of o- or w-cresol and at 110° to 120° C. for >-cresol. 

Unlike the corresponding rc-cresol derivatives, these dichlorides are not readily transformed into triarylated tellurium chlorides by prolonged boiling with 95 per cent, alcohol or with aqueous sodium carbonate. 

Bis[morpholino] tellurium dichloride was also obtained from bis[tetrafluoropropoxy] tellurium dichloride or tris[tetrafluoropropoxy] tellurium chloride and iV-trimethylsilyl-morpholine3. 

Tellurium tetrakis[fluoroalkoxides] and tellurium tetrachloride reacted in refluxing benzene or tetrahydrofuran to produce fluoroalkoxy tellurium chlorides. The number of alkoxy groups in the product molecules is determined by the molar ratio of the reagents2. 

Under similar conditions but with three moles of tellurium tetrakis[fluoroalkoxide] per mole of tellurium tetrachloride, tris fluoroalkoxy] tellurium chlorides were obtained2. 

Fluoroalkoxy tellurium chlorides react with N-trimethylsilylmorpholine in diethyl ether at 5° with preferential replacement of fluoroalkoxy groups. Only two morpholino groups can be introduced into the molecules, even when an excess of the amine is used1. 

Tellurium chloride pentafluoride added under illumination to cyanogen chloride or to trifluoromethyl cyanide, formed an imino tellurium pentafluorides1 2 as colorless liquids. 

Dichloromethyleneamino Tellurium Pentafluoride2 Equimolar quantities of tellurium chloride pentafluoride and cyanogen chloride are loaded into a 61 Pyrex flask to give a pressure of approximately 1 atm at 20°. This mixture is irradiated for 5 h with an internal low-pressure mercury lamp. The volatile products are distilled under vacuum through a series of traps at — 70°, — 110°, and —196°. The trap at — 70° contained the crude product. A series of photolysis reactions starting with 150.7 g of tellurium chloride pentafluoride yielded 82.3 g crude product that is distilled on a 100-cm spinning-band column at 76 torr yield 59.7 g (32%) b.p. 63-65776 torr. 

Chloro(trifluoromethyl)methyleneamino tellurium pentafluoride was similarly prepared2 from tellurium chloride pentafluoride and trifluoromethyl cyanide. The product could be purified only by preparative gas chromatography on a 15% Halocarbon K-352 column. The vapor pressure of the pure compound was 50 torr at 25°. 

Organic tellurium compounds with one Te—C bond containing divalent, tetravalent, or hexavalent tellurium have been prepared. The most widely investigated and best characterized compounds are the diorgano ditellurium derivatives and the organo tellurium trihalides. Pentafluoroethyl tellurium chloride tetrafluoride is the only known example of a hexavalent tellurium compound with one Te-C bond in the molecule. 

Cl 1 R-Te-NR2 1 Cl aryl tellurium chloride amides X / R-Te n-so2-r aryl tellurium chloride arenesulfonimide aryl tellurium morpholidc arenesulfonimide... 

Phenylazo)phenyl tellurium chloride reacted with sodium dithiocarbamates at room temperature to give 2-(phenylazo)phenyl dithiocarbamato tellurium compounds3. 

Phenylazo)phenyl Dialkyldithiocarbamato Tellurium3 A solution of the sodium dialkyldithiocarbamate (1.03 mmol) in 15 ml dry methanol is added under an atmosphere of nitrogen to a stirred solution of 2-(phenylazo)phenyl tellurium chloride (0.35 g, 1.0 mmol) in dichloromethane (25 ml). The mixture is stirred for 20 min at 20°. The solvents are removed on a rotary film evaporator. Dichloromethane is added to the residue. The mixture is vigorously stirred and the solution is filtered to remove the sodium chloride. 

Phenylazo)phenyl tellurium acetate was prepared from the aryl tellurium chloride and sodium acetate. The tellurium atom is in a trigonal bipyramidal environment with the oxygen and one nitrogen atom in the two axial positions1. 

Only a few unsubstituted, non-stabilized alkyl tellurium halides were characterized or isolated. /-Butyl tellurium chloride may have been detected by l2STe-NMR spectroscopy as a minor product of the controlled chlorination of di-/-butyl ditellurium6. 2-Chlorocarbon-ylbenzyl tellurium halides were obtained as rather unstable solids by halogenolysis of tellurophthalide7 (p. 246). Tris[trimethylsilyl methyl tellurium chloride, bromide and iodide were isolated as black-blue crystals that were stable in solution and as solids8. The stability of these compounds is attributable to the steric protection of the Te —X group by the trimethylsilyl substituents. 

The possibility of preparing aryl tellurium halides from equimolar amounts of diaryl ditellurium compounds and aryl tellurium trihalides has hardly been explored. Only phenyl tellurium iodide and 2-biphenylyl tellurium bromide could be obtained by this route. The other aryl tellurium halides (including 3,4-dimethoxyphenyl tellurium chloride) decomposed under the reaction conditions to give diaryl tellurium dihalides and tellurium5. 

When the thiosemicarbazones of benzaldehyde, 2-hydroxybenzaldehyde, methyl phenyl ketone, or methyl 2-hydroxyphenyl ketone were reacted with aryl tellurium trichlorides, reduction to the aryl tellurium chlorides occurred. The aryl tellurium chlorides were stabilized by coordination to excess thiosemicarbazone2. 

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