Of tellurium compounds

Caution Because tellurium compounds have toxic effects similar to those of arsenic compounds care should be taken not to bring tellurium tetrachloride and its reaction products into contact with the skin. Avoid breathing fumes and dust of tellurium compounds. In addition, hydrogen chloride is evolved in Step A, and pyrophoric Raney nickel is used in Step B. Therefore all manipulations described in this procedure must be carried out in an efficient fume hood. 

These classes of tellurium compounds are treated separately because of their peculiar behaviour as synthons and intermediates of fundamental organic transformations. ... 

Further examples of reductive detelluration of tellurium compounds have been shown in connection with tellurolactonization and telluroetherification reactions (see Section 4.5). 

Tellurium forms inorganic compounds very similar to those of sulfur and selenium. The most important tellurium compounds are the tellurides, halides, oxides, and oxyacids (5). Techniques and methods of preparation are given in the literature (51,52). The chemical relations of tellurium compounds are illustrated in Figure 2 (53). 

Transformations of heterocycles with participation of tellurium compounds 91S793, 91S897. 

Tellurium Ttis(A -methyl-. V-2-hydroxyettiyldithiocarbamate) Thiocyanate3 A sample of tellurium tris[/V-methyl-Af-2-hydroxyethyldithiocarbamateJ chloride is dissolved in 30 ml of methanol. A methanolic solution of potassium thiocyanate (5 mmol/mmol of tellurium compound) is added. The product precipitates immediately. The crystals are collected, washed with methanol, and rccrystallized from hot methanol yield 80% m.p. 140°. 

The following types of tellurium compounds with one Te-C bond in the molecule are known ... 

Aryl triphenylstannyl tellurium reacted with 1,5-cyclooctadienedichloropalladium in chloroform at 20°. With equimolar amounts of the reagents 1,5-cyclooctadienechloro (arenetellurolato)palladiums were isolated with 2 moles of tellurium compound per mole of palladium complex, 1,5-cyclooctadiene bis[arenetellurolato]palladiums were obtained2. 

Tellur oformaldehyde is the only representative of this class of tellurium compounds that has been isolated. Tclluroformaldehyde was prepared by passing carbene, generated by the decomposition of a diazomethane/diethyl ether mixture below 500°, over tellurium... 

Only two representatives of this class of tellurium compounds are known. They were prepared in quantitative yields from diphenyl tellurium iodide cyanide and silver pseudohalides2. 

While the chemistry of tellurium compounds is still in its infancy, the rapid recent progress has shown that tellurium has many unique properties compared to other chalcogen elements. The advent and development of modem... 

The tellurium alkoxide trichlorides were isolated as adducts containing one mole of alkyl acetate per two moles of tellurium compound. ... 

Dicyclohexyl tellurium dibromide formed complexes with pyridine, piperidine, mor-phohne, diethylamine, 4-bromoaniline, dimethylformamide, and dimethyl sulfoxide. The complexes have two molecules of ligand per molecule of tellurium compound . Bis[benzoylmethyl] tellurium dibromide formed 1 2 complexes with cyclic amines. ... 

The special nature of the Tellurium compounds forced a change of the set-up principle of the Supplemental Volumes of the 4 edition to some extent, but all classes of Tellurium compounds with at least one carbon atom, which must not necessarily be bonded to the Tellurium atom, will be described, and also esters of the different Te-containing acids. The set-up will be easily understood from the Table of Contents. Since the chemistry of the organic Tellurium compounds has grown tremendously during the past 35 years, there will be only few references to volume IX of 1955 therefore, volume El 2b stands more or less by itself. 

These classes of tellurium compounds are treated separately because of their peculiar behaviour as synthons and intermediates of fnndamental organic transformations. Leading examples of snch performance are the transmetallation reactions of (Z)-vinylic tellurides, easily generated by the hydrotellnration of alkynes, leading to (Z)-vinyl organometallic reagents, which are difficnlt to obtain by other cnrrently available methods. 

Among a series of trifluoromethyl dibenzoheterocyclic onium salts derived from chalcogens, a small number of tellurium compounds have been prepared. As electrophilic trifluoromethylating agents, the tellurium compounds appeared as the least reactive. With a very reactive carbanion, the unsubstituted dibenzotellurophenium salt (81) gave only 9% of the trifluoromethylated product. With the p-diketone enolate, (81) did not react. However, the 3,7-dinitrotellurophenium salt (82) showed a relative activity similar to that of the unsubstituted selenium compound (47). 1... 

There is no quantitative information available on the respiratory absorption of tellurium compounds in humans. In animal experiments, elemental tellurium and tellurium dioxide was very poorly absorbed from the gastrointestinal tract, but about 25% of ingested water-soluble tellurites and tellu-rates were absorbed and distributed in tissues (Hollins 1969). Absorption of tellurium in the alimentary canal is complete within 2 h of ingestion. In rats, absorption occurs mainly in the duodenum and jejunum, and total absorption is estimated to be 10-25% (Slouka 1970). When injected into rats, tellurium is distributed rapidly into... 

The biological half life of tellurium in rats after injection of tellurium compounds is 19 h for about half (42.49%) of the dose, and 13-15 days for the remainder (51-58%) of the dose. Hence, total clearance from humans is complete in about 3 weeks. The estimated biological halftimes in blood, liver, muscle, and kidney of rats are 92, 10.2, 17.7, and 23 days, respectively. Because bone dose not release deposited tellurium, an approximation of the halftime in bone is 600 days (Hollins 1969). 

OTHER COMMENTS tellurium may be used as a coloring agent in chinaware, enamels, porcelains, and glass utilized in the manufacture of special alloys of marked electrical resistance has also been used in the manufacture of electronic devices such as batteries, solar cells, semiconductors, and during the manufacture of tellurium compounds. 

In a quasirelativistic Hartree-Fock study of Te shifts in a number of tellurium compounds [47], SFR effects were relatively small even for the absolute shieldings and further cancelled out in the relative shifts. The same was foxuid in scalar relativistic DFT calculations [5,42,118]. Third-order SO effects, which were also considered in [47], were significant for shieldings but again largely cancelled for relative shifts. This confirms that HAHA SO effects on... 

---