From sodium ditelluride and alkylating agents

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. 

Dimethyl ditelluride (typicalprocedure. Clean Na metal (3.2 g, 0.14 mol) is added to 100 mL of liquid NHj at 78°C. After stirring for 1 h, high-purity powdered Te (18.2 g, 0.14 mol) is added in 0.5 g portions. Methyl iodide (24 g, 0.17 mol) is then added dropwise for 20 min, with stirring, to the dark green solution. The NHj is evaporated, H2O is added to the residue and the mixture extracted with ether (4X50 mL). The combined deep red extracts are dried overnight (CaCy, and evaporated under vacuum. The residue is then distilled (7.6 g (38%) b.p. 97°C/9 torr). 

Diethyl ditelluride and dibenzyl ditelluride are prepared similarly in yields of 71% and 82%, respectively. 

Dialkyl ditellurides (general procedure A mixture of powdered Te (3.58 g, 28 mmol), Na chips (0.65 g, 28 mmol) and naphthalene (0.36 g, 2.8 mmol) in anhydrous THF (25 mL) is refluxed under Nj and stirred for 1 h. During this time all the sodium is consumed and the mixture turns a light brown colour. The solution is stirred for an additional 3 h to ensure the complete reduction of Te, the temperature is then lowered to 10°C and the alkyl hahde (28 mmol) is added dropwise for 30 min with stirring. After an additional hour of stirring at room temperature, the reaction mixture is filtered, the solvent evaporated and the residue distilled under vacuum, giving the pure ditelluride (R=Et (85%), n-Pr (90%), n-Bu (90%), MeOCHjCHj (60%)). 

Dialkyl ditellurides (general procedure) Powdered Te (6.35 g, 50 mmol) is added to a stirred solntion of NaOH (3.0 g, 75 mmol) in deoxygenated H2O (20 mL). The mixture is cooled in a water bath, and 100% hydrazine hydrate (2.5 g, 200 mmol) is added over a period of 30 min and stirring is continned for an additional honr at room temperature. The aUcyl halide (50 mmol) is then added dropwise over a period of 2-3 h. Dnring the addition, the temperature is maintained at 15-20°C. The end-point of the alkylation is indicated by a sharp colour change from dark brown to nearly colourless. The mixture is then extracted with ether, the organic layer is washed with H2O, dried (Na2S04) and the solvent removed by slow distillation. The residue is distilled under vacuum. 

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