Tellurides telluride dihalides

Diorganyltellurium dihalides can also be prepared by the addition of halogens to the parent tellurides. 

When the alkylating agent is insoluble in liquid ammonia, as in the case of long-chain compounds, an organic solvent is added to the sodium telluride residue after evaporation of the ammonia. Some cyclic and steroidal tellurides have been prepared from sodium telluride in ethanol and the appropriate dihalides. ... 

With sodium sulphide hydrate (general procedure) The diorganyltellurium dihalide is mixed with a 15 times molar excess of Na2S 9H2O and the mixture heated at 95-100°C for 10 min or more, until aU the solid has melted. Sufficient HjO is added to dissolve the sulphide and then the mixture is filtered if the obtained telluride is a solid, or extracted with a solvent (ether or petroleum ether) if the telluride is a liquid. The products are purified by crystallization or distillation. Yields are high or quantitative (except for diphenyl telluride or di-p-tolyl telluride). 

Diaryltellurium dihalides (general procedure) The diaryl telluride dissolved in a small amount of benzene or CHCI3 is treated dropwise, while cooling (ice bath) and stirring, with a solution of an equimolar amount of SO2CI2, Br2 or I2 in the same solvent (in the case of SO2CI2, evolution of SO2 is observed). By addition of a large excess of petroleum ether at 30-60°C (50 mL for 1 mmol) the dihalide precipitates as a crystalline solid (the dichlorides are colourless, the dibromides yellow and the diiodides red). The yields are quantitative. 

Organic tellurides are known and clearly show the tendency of tellurium to pass from the bivalent condition to one of higher valency 2 thus the dialkyl tellurides act in an unsaturated manner and readily form dihalides, oxides and hydroxides, for example, (C,H5)2TeCl2,... 

Drew (J. Chem. Soc., 1929, p. 568) considers that the /5-dihalides do not give dimethyl telluride on reduction, but an orange oil of carbylamine odour, probably dimethyl ditelluride. 

The diaryl tellurides combine with halogens to form dihalides, R2TeX2, and with mercuric halides mercurihalides are produced, R2Te.HgX2. 

The reaction of aryltellurium trichlorides 116 with activated aromatics 117 gives the corresponding diaryltellurium dihalides 118, which by reduction give the diaryl tellurides 119.5 11 12 55... 

The following cyclic tellurium compounds were prepared from sodium telluride in ethanolic solution and the appropriate organic dihalides ... 

When organic dihalides with five atoms between the two halogen atoms were reacted with disodium telluride, prepared by the Rongalite method, the corresponding telluranes were formed2-6. 

A reaction sequence starting with bis[phenyltelluro]mcthane leads to the insertion of a methylene group into the carbon-halogen bond of an alkyl halide. The bis[phenyltelluro] methane is reacted with butyl lithium to yield lithiomethyl phenyl telluride, which combines with an alkyl halide. The resulting alkylmethyl phenyl tellurium is converted to the tellurium dihalide, which in turn decomposes to an alkylmethyl halide when kept under vacuum at 250 6 or heated in DMF in the presence of a sodium halide at 100°7. 

Lithium telluride, prepared from tellurium and lithium triethylborohydride in tetrahydrofuran2, and sodium telluride, obtained from sodium and tellurium in a dipolar, aprotic solvent or from tellurium2,5 and Rongalite in aqueous sodium hydroxide2, reacted with aliphatic2,3,6 and aromatic5 dihalides to produce polymeric organo tellurium compounds. 

Most diorganyltellurium dihalides are stable in air. This facilitates a convenient method to purify diorganyl tellurides that are liquid at room temperature. The raw product is converted to a dichloride or dibromide by direct chlorination or bromination, and the pure dihalides are easily be reduced back to the original telluride." ... 

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