By addition of halogens to diorganyl tellurides

The reaction with ethyl- and cyclohexytmercury chlorides requires heating for 24 h. 3.9.4 By addition of halogens to diorganyl tellurides 

Diorganyl tellnrides, which as shown in Section 3.1 are the primary products of several methods for the synthesis of organotellurium compounds, can easily be converted into the corresponding dihalides by the simple addition of halogens. 

This reaction has a general character and can be applied to the different types of telluride. The halogenation is accomplished in inert solvents (ether, benzene, dichloromethane and chloroform) and the dihatides are normally easily crystaUizable products. 

The chlorination of tellurides is more conveniently done by using, instead of chlorine (gaseous or dissolved in solvents), chlorinating reagents such as sulphuryl or thionyl chloride (Uke the chlorinolysis of ditellurides, see Section 3.5.2). 

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. 

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