Tellurium Derivatives with

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). 

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. 

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. 

Benzenetellurinyl trifluoroacetate and allyltrimethylsilanes reacted in 1,2-dichloroethane at 20° in the presence of boron trifluoride diethyl etherate to produce allyl phenyl telluroxides. The unstable telluroxides were not isolated but detected in solution by NMR spectroscopy. They were reduced to allyl phenyl tellurium derivatives with hydrazine hydrate. 

All tellurium derivatives with exception of the diorgano tellurium diselenocyanates have infrared absorption bands in the regions that would indicate N—Te bonding. The frequencies for v(c—Se) in the diorgano tellurium selenocyanates (598 cm- ) fall between the frequencies for organic iso selenocyanates (630 + 20 cm-1) and those for normal selenocyanates (550-520 cm- ). 

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... 

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. 

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. 

The group VIB cyanides, thiocyanates and selenocyanates and their complexes with species such as thiourea have been described.1,45 For example, the tellurium dithiocyanate complex has been prepared45 by treatment of tellurium dichloride or tellurium dibromide with ammonium thiocyanate. It seems that little information exists on the preparation of tellurocyanates and there is a sparsity of data on polonium derivatives. Indeed, the only known cyanide of polonium is probably a salt of the quadrivalent element.1... 

Dimethyl telluride, (CH3)2Te.—The method first used for isolating this substance consisted in treating a potassium-tellurium alloy with a concentrated aqueous solution of barium methyl sulphate.1 It appears doubtful whether the method can actually be used for obtaining dimethyl telluride itself, although it might be used for derivatives of this body. An excellent yield of dimethyl telluride is obtained according to the equation 2... 

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). 

The stepwise lithiation of 1,8-dibromonaphthalene and related derivatives with subsequent capture of sulfur, selenium or tellurium after each lithiation has generated naphtho[l,8-ccf][l,2]dichalcogenoles (2), (11), (21), (34) and (83) (77JA7743). The closely related compounds (105) and (106) have been generated in a similar fashion (80TL4565). 

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. 

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. 

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

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

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. 

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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