Tellurides routes

A comprehensive work on the electrodeposition chemistry and characterization of anodically synthesized CdTe thin films has been presented by Ham et al. [98]. In this work, along with the electrolytic anodic synthesis of CdTe by using Cd anodes in alkaline solutions of sodium telluride, an electroless route of anodizing a Cd electrode held at open circuit in the same solution was also introduced. The anodic method was expected to produce CdTe with little contamination from Te on account of the thermodynamic properties of the system the open-circuit potential of Cd anodes in the Te electrolyte lies negative of the Te redox point, so... 

Hydrogen sulfide can be prepared from the elements, but the unfavorable heat of formation of H2Se and H2Te indicates that producing them by direct combination is not a efficient route. Instead, they are first obtained as selenides and tellurides, which then react with an acid. 

Attempts to synthesise tritellurophosphonic acids or their salts have so far proved unsuccessful, and synthetic routes from primary phosphines analogous to Equation 39 with E = Te give just cyclic polyphosphanes (RP) and lithium telluride with no observed tritellurophosphonate formation.45... 

A more extensive and detailed study of these reactions (i. e. 32 to 33) was carried out by Dabdoub et al., who found that two equivalents of Cp2Zr(H)Cl are needed for complete consumption of acetylenic tellurides 35 (Scheme 4.24) [51]. Solubilization of Cp2Zr(H)Cl in the reaction medium (THF) is apparently not a sufficient indication of educt consumption when only 1.1 equivalents are employed (e. g., following a proton quench, 58% of the product 37 and 41% of the acetylenic telluride 35 were recovered). Furthermore, care must be taken to avoid Cp2ZrH2, potentially present following the Buchwald route [3] to Cp2Zr(H)Cl, since Csp—Te bond reduction can occur to a significant extent in the presence of this dihydride or of residual LAH. 

As an alternative to hydrozirconation of acetylenic tellurides or selenides, Dabdoub and co-workers have more recently described the first additions of the Schwartz reagent (one equivalent) to acetylenic selenide salts 51 (Scheme 4.30) [52]. Subsequent alkylation at selenium produces 1,1-dimetallo intermediates 52, which are cleanly converted in a one-pot process to stereodefined products 53. It is noteworthy that ketene derivatives 52 are of ( )-geometry, the opposite regiochemistry to that which results from hydrozirconation of acetylenic tellurides (vide supra). This new route also avoids the mixtures of regio-isomers observed when seleno ethers are used as educts. The explanation for the stoichiometric use of Cp2Zr(H)Cl in these reactions, in contrast to the requirement for two equivalents with seleno ethers, may be based on cyclic intermediates 54, in which Li—Cl coordination provides an additional driving force. Curiously, attempted hydrozirconation of the corresponding telluride salt 55 under similar conditions was unsuccessful (Scheme 4.31) (Procedure 12, p. 143). 

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. 

This is the most direct route to diorganyl ditellurides and therefore parallels the ronte leading to diorganyl tellnrides, snbstitnting sodium telluride for sodium ditelluride. Sodium ditelluride is prepared employing, with the appropriate ratio of the elements, methods analogous to those described for sodium telluride. 

The Grignard route to diorganyl ditellurides suffers from lack of generality and the mechanism of the oxidation seems to be uncertain. Alkylmagnesium halides demonstrate lack of reactivity towards elemental tellurium/ whereas aryhnagnesium halides in ether as the solvent furnish a mixture of ditellurides and tellurides. Satisfactory results are obtained by tellurium insertion in aryhnagnesium halides in THF followed by oxidation before or after aqueous work-up. ... 

Vinylic tellurides via olefination reactions 3.16.5.1 Homer-Emmons route... 

Trimethylsilylphenyl telluride, by treatment with benzophenone in MeCN at room temperature, gives compound A which is treated in sequence with phenylacetylene at 100°C to give compound C in 85% yield (route a). The reaction can also be performed in one step by heating a mixture of the telluride (1.2 equiv), benzopheuone (1.0 equiv) and phenylacetylene (1.2 equiv) without solvent at 100°C for 12 h to give C in 93% yield (route b). 

In this edition, we have incorporated new material in all the chapters and updated references to the literature. New sections dealing with porous solids, fullerenes and related materials, metal nitrides, metal tellurides, molecular magnets and other organic materials have been added. Under preparative strategies, we have included new types of synthesis reported in the literature, specially those based on soft chemistry routes. We have a new section covering typical results from empirical theory and electron spectroscopy. There is a major section dealing with high-temperature oxide superconductors. We hope that this edition of the book will prove to be a useful text and reference work for all those interested in solid state chemistry and materials science. 

Although conventional solar cells based on silicon are produced from abundant raw materials, the high-temperature fabrication routes to single-crystal and polycrystalline silicon are energy intensive and expensive. The search for alternative solar cells has therefore focused on thin films composed of amorphous silicon and on other semiconductor heterojunction cells (e.g., cadmium telluride and copper indium... 

Another route to alkyl vinyl tellurides of (Z)-configuration recently developed is shown in Scheme 45.154... 

The hydrozirconation of alkynes is a well-established reaction, giving vinylic zirconium species of known regio-and stereochemistry.176 These species react with aryltellurium halides leading to vinylic tellurides with the ( )-stereochemistry 98 (Scheme 61),177,178 so complementing the other general routes to these compounds which give preferentially the (Z)-products (Sections 9.13.5.2.3, 9.13.5.2.5). 

Z)-vinylic tellurides are the source of enynes 212 and enediynes 213 by transformation into vinylcopper species (Section 9.13.8.2.4), followed by reaction with haloalkynes (Scheme 113).278,279 The transformation occurs with retention of the double-bond stereochemistry. This is an efficient and straightforward route to important unsaturated units present in natural products, specially in enediyne antibiotics.280... 

The sodium borohydride method appears to be the most convenient and most widely applicable route to dialkyl telluriums. Sodium dithionite was also used to prepare disodium telluride11, which subsequently was reacted with methyl, ethyl, propyl, and pentyl halides. Tellurium was also electrochemically reduced to the telluride anion in an ultrasonically aided reaction15 using tellurium powder in acetonitrile, and to the tetratelluride dianion with a tellurium rod as cathode and sodium perchlorate in dimethylformamide as electrolyte16. 

Unsymmetrical dialkyl tellurium derivatives were prepared by mixing an aqueous disodium telluride solution with equimolar amounts of two different alkyl halides. All three possible dialkyl tellurium products are formed. The unsymmetrical dialkyl tellurium is the predominant species. It can be separated from the symmetrical compounds by chromatography1. This one-pot procedure takes less time to complete than the alternative route employing alkyl tellurolates (p. 387) and was used to prepare unsymmetrical dialkyl telluriums containing radioactive tellurium. Sequential addition of two alkyl halides produced only symmetrical dialkyl telluriums. 

An alternative route to telluronocarboxylic acid amides starts with thionoamides that are converted by methyl iodide to (methylthio)organomethyleneiminium iodides. The iminium iodides react with hydrogen telluride at below — 40° to give telluronoamides. 

Binary tellurides are generally solid crystalline substances at room temperature. The most common structural classes have been presented in Table 4. The telluride bulk materials are commonly prepared by the direct reaction between the elements. In recent years, low-temperature routes from transition metal complexes with tellurium-containing ligands are being sought for. 

The original synthesis of diethyl teUnride by Wohler was carried out by treating potassium telluride with ethyl sulfate. The preparation of potassium telluride was rather inconvenient and involved the reduction of elemental tellurium by heating the element at red heat with potassium-hydrogen D-tartrate. An early report of Natta demonstrated that the treatment of aluminium telluride by alcohols or ethers at 250-300 °C is also a promising route to diorganyl tellurides. 

The main routes to symmetrical diorganyl tellurides involve the direct reaction of nucleophilic telluride dianions (usually as Nii Tc) with alkylating or arylating reagents. Otherwise the electrophilic tellurium tetrahalides react with aryhnagnesium reagents, giving diaryl tellurides. 

Internal vinyl tellurides, which are not accessible via hydroteUuration of alkynes, have been prepared from alkynes through a vinyl borane route. 

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