Tellurium halides, preparation

The coordinatively unsaturated aryl tellurium halides interact with electron-donor ligands to form complexes. The aryl tellurium halides prepared from diphenyl ditellurium and halogens were used in situ. Thiourea, selenourea (X = Cl, Br)3, tetramethylthio- and... 

Okazaki247 also suggested a detailed mechanism for the preparation of 1,3,4-telluradiazoline from 1,1,3,3-tetramethylindanhydrazone and tellurium halides. The reaction produces a complicated mixture of products, including 12. 

Tellurium Halides. Tellurium forms the dihalides TeCl and TeBi, but not Tel2. However, it forms tetrahalides with all four halogens. Tellurium decafluoride [53214-07-6] and hexafluoride can also be prepared. No monohalide, Te2X2, is believed to exist. Tellurium does not form well-defined oxyhalides as do sulfur and selenium. The tellurium halides show varying tendencies to form complexes and addition compounds with nitrogen compounds such as ammonia, pyridine, simple and substituted thioureas and anilines, and ethylenediamine, as well as sulfur trioxide and the chlorides of other elements. 

The tellurium bis[alkyl trithiocarbonates] need not be isolated. The dichloromethane or chloroform extract of the aqueous reaction mixture containing the tellurium compound can be treated with bromine or iodine1. Examples of tellurium (alkyl trithiocarbonate) halides prepared in this manner are ... 

Organo tellurium halides, also named organo tellurenyl halides, are in principle easily accessible through controlled halogenolysis of diorgano ditellurium compounds. However, 2-naphthyl tellurium iodide, prepared in 19592 from bis[2-naphthyl] ditellurium and iodine, remained the only compound of this type until 1971/72, when a series of ortho-carbonyl substituted phenyl tellurium halides were synthesized3-4. Aryl tellurium halides without substituents in the ortho-position to tellurium were isolated and characterized in 1975s. 

Aryl tellurium bromides and iodides can be obtained by reaction of diaryl ditellurium compounds with an equimolar amount of bromine or iodine, when the solvent is able to dissolve the starting materials but not the aryl tellurium halide. The precipitation of the aryl tellurium halide prevents it from being converted to aryl tellurium trihalides. The aryl tellurium halides thus far isolated and suitable reaction media for their preparation are listed in Table 3 (p. 240). 

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. 

Alkyl tellurium halides, RTeX, in general, have no importance as starting materials for the preparation of alkyl tellurium trihalides. The alkyl tellurium halides are synthesized from dialkyl ditellurium compounds and elemental halogens. When alkyl tellurium trihalides are the desired products, there is no reason to prepare the monohalides first. However, when the tellurium monohalide is formed during the introduction of tellurium into an organic molecule, the reaction of this primary product with halogens is the method of choice for the preparation of the tellurium trihalides. This situation is realized for 3-oxo-l-propen-l-yl tellurium halides2,3. 

Oxo-1-propen-1-yl tellurium iodides did not react with iodine. The attempt to prepare mixed (chloride, bromide) tellurium trihalides was unsuccessful a mixture of trichlorides and tribromides was formed. When 1,3-diphenyl-3-oxo-l -propen-l-yl tellurium iodide was reacted with bromine, the bromide and elemental iodine were the only observed products. The 3-oxo-l-propen-l-yl tellurium trihalides are thermally unstable they decompose on mild heating to the tellurium halide and elemental halogen1. 

Aryl tellurium halides have the capability of adding to carbon-carbon double bonds. This potentially useful method for the preparation of aryl alkyl tellurium compounds has been used to prepare 2-naphthyl 2-oxo-3,3-diphenyl-5-furylmethyl tellurium (yield 61 %)6. 

Diaryl ditellurium compounds and aryl tellurium trihalides react in refluxing 1,2-dichloroethane to form diaryl tellurium dihalides and tellurium. The reactions are postulated to proceed via aryl tellurium halides that disproportionate into tellurium and diaryl tellurium dihalides. All reactions of this type thus far carried out on a preparative scale used pairs of reagents with the same aryl group2. 

Alkyl organo tellurium compounds, prepared from alkane- or arenetellurolates and alkyl halides, react with butyl lithium,. 9ec-butyl lithium, /ert.-butyl lithium, or phenyl lithium. The alkyl group bonded to the tellurium atom is cleaved from the tellurium and is present in solution as the alkyl lithium that can be used for further reactions. This tellurium-lithium exchange reaction is synthetically useful, whenever the alkyl halides cannot be converted to alkyl lithiums by other, more conventional halogen exchange reactions. The following exchange reactions were successfully carried out ... 

In this paper a short survey of the group of tellurium halides is followed by detailed information on phase relations, preparation, crystal growth, and crystal structures of tellurium subhalides. Moss-bauer investigations as well as optical, photoelectric, and electrical properties of the respective compounds are discussed. Sohd-state galvanic cells containing tellurium subhalides have enabled the precise determination of relevant thermodynamic data. 

Sulphenyl Halides.—This section describes first the preparations of sulphenyl halides of particular interest in the recent literature, then their properties and their addition and substitution reactions. More space is allocated this year for results from studies of organo-sulphur, -selenium, and -tellurium halides involving higher valency states. 

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