Tellurium derivatives

The aim of this chapter is to review the chemistry of chalcogenolates in the last 10 years. The more recent reviews in this field included chalcogenolates of the s-block elements,13,14 early transition metal thiolates,15 metal complexes with selenolate and tellurolate ligands,16 copper(I), lithium and magnesium thiolates,17 functionalized thiolate complexes,18 19 pentafluorobenzenethiolate platinum group compounds,20 tellurium derivatives,21 luminescent gold compounds,22 and complexes with lanthanide or actinide.23... 

The lesser electrophilicity of the selenium and tellurium derivatives is also displayed in their hydrolytic stability. In general, all diselenonium dications are more stable toward hydrolysis than the corresponding disulfonium dications. 1,5-Diselenoniabicyclo[3.3.0]octane 113, which is expected to be hydrolyzed to an unstable selenoxide, is stable in water.124 On the other hand, dication 112 is... 

In contrast to the cathodic reduction of organic tellurium compounds, few studies on their anodic oxidation have been performed. No paper has reported on the electrolytic reactions of fluorinated tellurides up to date, which is probably due to the difficulty of the preparation of the partially fluorinated tellurides as starting material. Quite recently, Fuchigami et al. have investigated the anodic behavior of 2,2,2-trifluoroethyl and difluoroethyl phenyl tellurides (8 and 9) [54]. The telluride 8 does not undergo an anodic a-substitution, which is totally different to the eases of the corresponding sulfide and selenide. Even in the presence of fluoride ions, the anodic methoxylation does not take place at all. Instead, a selective difluorination occurs at the tellurium atom effectively to provide the hypervalent tellurium derivative in good yield as shown in Scheme 6.12. 

Germacyclopropabenzene 3 can react directly with elemental chalcogens to yield bicyclic chalcogenagermetes 83 (Equation (146)).193 The structure of the tellurium derivative 83c is shown in Figure 4 and structural information is... 

One of the first series of reports on ultrasonically-enhanced electrosynthesis was by Gautheron, Tainturier and Degrand [69] who used the technique to explore routes to organoselenium and tellurium derivatives. Instead of employing a sacrificial cathode of elemental selenium, their procedure allowed the direct use of selenium powder with carbon cloth as cathode to produce Se and Se. A further benefit was that this method also allowed production of the corresponding tellurium anions. These species could be employed in situ in aprotic solvents such as DMF, THF and MeCN for the synthesis of selenides and tellurides by nucleophilic displacement from haloalkanes. 

PhCOC5H4SePh and 45 % for the tellurium analogue are obtained. Interestingly, the isolated yield for the tellurium derivative under mechanical stirring was 44 %. Such a little difference between the mechanical stirred yield and the sonoelectrochemical yield, makes the role of ultrasound in such complex systems difficult to ascertain. 

The intennediates in these reactions are the corresponding triaryltelluronium halides (which react with an additional equivalent of Grignard reagent) or the unstable tetraaryl-tellurium derivatives. 

No tellurium derivatives of M3E7X6-type compounds had been described until Fedin et al. reported the synthesis of Mo3Te10I10 from the reaction of molybdenum, tellurium, and iodine at 398°C for 48 hr in a sealed tube (119). The structure (Fig. 30) is composed of [Mo3(/t3-Te)(/x2-... 

During work on nucleophilic substitution at divalent sulfur,64 65 a series of tellurium derivatives with sulfur-containing ligands were prepared in a straightforward manner by addition of a warm aqueous solution of, for example, thiourea to tellurium dioxide dissolved in warm hydrochloric or hydrobromic acid, and which involved the reduction of tellurium(IV) to tellurium(II). 

Certain tellurium derivatives of the aliphatic /3-diketones, for example, cj/clotelluropentane-3 5-diones of the type... 

It is evident from the foregoing condensations that a branched chain inhibits the formation of a cyclic dichloro-tellurium derivative containing the bivalent diketone radical. Hence j8-diketones with terminal branched chains (RR CH.CO. and RR CH.CH2.CO.) cannot be employed in the production of yellow cyclic tellurium derivatives such as are obtained from w-butyrylacetone. 

The hydrolysis of seleno- and telluropyrylium dyes involves nucleophilic addition of water to the substrate. a,f3-LJnsaturated selones and -tellones 60 are intermediates in this reaction (Equation 22) <1997JOC4692, 1998JOC5716>. Diketones are the primary hydrolysis products isolated in high yields from these reactions. The tellurium derivative hydrolyzes most rapidly over the pH range 3-12, with the sulfur analogue least reactive under these conditions. Seleno- and telluropyrylium dyes are important both for their biological activities and potential industrial applications (see Section 7.11.8). 

Fig. 14.35 Representative 5,6,11,12-tetrachalcogenotetracenes (top), showing the solid-state ordering and intermolecular overlap for the sulfur derivative 46 (center) and the tellurium derivative 47 (bottom).

Tellurium derivatives of inorganic nature, such as tellurium dihalides, that form coordination compounds with organic ligands, such as thiourea and ethylenethiourea, are not included in this section. 

Divalent tellurium derivatives in which tellurium is bonded to two group IV elements, are known as linear and cyclic compounds. Symmetrical compounds with two silicon, germanium, tin, or lead atoms bonded to tellurium and unsymmetrical compounds, with two different group IV elements linked to tellurium have been prepared. Some of the compounds have an obnoxious odor4. 

The diorganophosphano trialkylsilyl(-germyl, -stannyl) tellurium compounds cannot be isolated because redistribution to the symmetrical tellurium derivatives takes place1-3. 

Dilithium telluride, prepared from lithium and tellurium in liquid ammonia2 4 or from tellurium and lithium triethylborohydride5, reacted with alkylhalosilanes and -germanes to yield disilyl and digermyl tellurium derivatives. 

The tellurium atom is easily eliminated from bis[trialkylsilyl] tellurium derivatives and the corresponding germanium and tin compounds. 

Tri-f-butylphosphane telluride and tris[dimethylamino]phosphane telluride combined with the corresponding phosphanes to give bis[triorganophosphane] tellurium derivatives. ... 

Tellurium and tetra-f-butyldiphosphane or tetraisopropyldiphosphane reacted to give bis[dialkylphosphano] tellurium derivatives. 

Bis[organothio] tellurium derivatives must be stored at temperatures below — 10°. At higher temperatures and in solution they decompose to tellurium and the diorgano disulfane2,3. 

Sodium tellurite, prepared by dissolution of tellurium dioxide in aqueous sodium hydroxide, reacted with carboxymethanethiol1 and with 1-carboxy-l-ethanethiol2 to form bis[carboxyalkylthio] tellurium compounds. The reactions must be carried out in acidic solutions, because base decomposes the bis[alkylthio] tellurium derivatives. With an excess of thiol, compounds with more than two alkylthio groups bonded to the tellurium atom were observed1,2. 

Tellurium tetrachloride and arenethiols in ethanol at — 8° produce bis[arylthio] tellurium compounds and diaryl disulfanes. Tetrakis[organothio] tellurium derivatives are likely intermediates in these reactions1. 

Bis[arylthio] tellurium derivatives reacted with methyl iodide at room temperature forming dimethyl tellurium diiodide and diaryl disulfanes2. 

The interest in coordination compounds containing transition metal-main group element bonds led to the preparation of tellurium derivatives, in which a bare tellurium atom is bonded to and bridges transition metal atoms such as Zr, Ilf, V, Cr, Mo, W, Mn, Re, Fe, Os, Co,... 

R-N=Te=N-R R = CO - CH3. S02-C6Hs bis[acetylimino] tellurium and bisfarenesulfonimino] tellurium derivatives... 

Arenesulfonimino bis[fluoroalkoxy] tellurium derivatives are moisture-sensitive solids. 

Fluorination of tetraalkoxy tellurium derivatives with a fluorine/nitrogen gas mixture in a medium of fluorotrichloromethane at —78° produced several alkoxy tellurium fluorides that could not be separated by distillation1.19F-NMR spectroscopy was used to identify the products and to determine their relative concentrations. 

These reductions were carried out in the presence of an alkyl halide that reacted with the sodium tellurolate. The expected unsymmetrical diorgano tellurium derivatives were isolated. 

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