From Dialkyl Tellurium Compounds

Diethyl tellurium, when heated with triethylsilane or triethylgermane at 200° or 140°, respectively, for seven hours, yielded ethyl triethylsilyl tellurium or the corresponding germanium compound  

Ethyl Triethylgermyl Tellurium Under an inert atmosphere, a mixture of 7.86 g (42 mmol) of diethyl tellurium and 8.0 g (50 mmol) of triethylgermane is heated at 140° for 7 h whereby 1100 m/ of ethane are evolved. The mixture is then fractionated under reduced pressure of nitrogen yield 5.2 g (39%) b. p. 61°/1 torr. 

Ethyl triethylsilyl tellurium (11% b.p. 53°/l torr) was similarly prepared by heating the reactants at 200°. Bis[triethylsilyl tellurium and bis[triethylgermyl] tellurium are also formed in these reactions .  

The tellurium-group IV element bond is the weakest bond in these molecules. Most reagents attack and cleave this bond. 

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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. 

Alkanetellurolates, that can be obtained from an organic lithium compound or a Grignard reagent and tellurium, are oxidized to dialkyl ditellurium compounds on contact with air. Di-t-butyl ditellurium, that is difficult to prepare by other routes, was obtained by this method in excellent yield1 2. The reaction of /-butyl magnesium chloride with tellurium proceeded in THF solution only in the presence of hexamethylphosphoric triamide2. 

Sodium alkanetellurolates, prepared by cleavage of the acetylene moiety from alkyl phenylethynyl tellurium compounds with sodium borohydride in ethanol or with hydrazine/sodium hydroxide (diimide) in ethanol, were oxidized to dialkyl ditellurium derivatives by air4. 

The halogenolysis of dialkyl ditellurium compounds is a convenient method for the preparation of alkyl tellurium trihalides because dialkyl ditellurium compounds are easily accessible through alkylation of disodium ditelluride (p. 258). Diaryl ditellurium compounds generally obtained via reduction of organo tellurium trichlorides (p. 274), serve as starting materials for the syntheses of aryl tellurium tribromides and triiodides (Vol. IX, p. 1156) that are not obtainable from the hydrocarbons and tellurium telrabromide or tetraiodide. 

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. 

Brominations are performed by dropping solutions containing the stoichiometrically required amount of bromine to the stirred solutions of the diorgano tellurium compounds. To prevent tellurium-carbon bond cleavage, which may occur with dialkyl and alkyl aryl tellurium compounds, the reactions should be performed at or below 20°. The likelihood of Te —C bond cleavage decreases from chlorine to iodine. 

Diorgano tellurium dihalides were prepared in this manner from dialkyl, alkyl aryl, and diaryl tellurium compounds, and from tellurium heterocycles. However, 1-oxo-1,3-dihydro-2-benzotellurophene experienced ring cleavage when reacted with sulfuryl chloride7. 

Lithium alkanetellurolates, prepared from tellurium and an alkyl lithium compound or dialkyl ditellurium derivatives and hthium, and sodium arenetellurolates, obtained from diaryl ditellurium compounds and sodium borohydride ", reacted with triorganosilyl, -germyl, -stannyl, and -plumbyl chlorides to produce, for instance, organo triorganosilyl tellurium compounds. 

Dialkyl, alkyl aryl, and diaryl tellurium dichlorides were reduced by thiourea dioxide in a 2 molar aqueous solution of sodium hydroxide to the corresponding diorgano tellurium compounds" The tellurium species actually reduced are the diorgano tellurium oxides or dihydroxides that are formed from the dichlorides in the basic medium. 

Complexes of the following elements with dialkyl and/or diaryl telluriums have been prepared B, Ga, Sn, V, Ta, Cr, Mo, Mn, Re, Fe, Ru, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Cd, and Hg. Examples of coordination compounds with diorgano telluriums as ligands are given in Table 14 (p. 489). The adducts of mercury(II) halides with diorgano telluriums were used in ihe older literature to separate diorgano telluriums from reaction mixtures (Vol. IX, p. 1057). 

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