Low Temperature Activation of Tellurium and Resource-Efficient Synthesis of AuTe and Ag Te in Ionic Liquids.

The low temperature syntheses of AuTe and Ag Te starting from the elements were investigated in the ionic liquids (ILs) [BMIm]X and [P ]Z ([BMIm] =1-butyl-3-methylimidazolium; X = Cl, [HSO ] , [P ]  = trihexyltetradecylphosphonium; Z = Cl , Br , dicyanamide [DCA] , bis(trifluoromethylsulfonyl)imide [NTf ] , decanoate [dec] , acetate [OAc] , bis(2,4,4-trimethylpentyl)phosphinate [BTMP] ). Powder X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy revealed that [P ]Cl is the most promising candidate for the single phase synthesis of AuTe at 200 °C. Ag Te was obtained using the same ILs by reducing the temperature in the flask to 60 °C. Even at room temperature, quantitative yield was achieved by using either 2 mol % of [P ]Cl in dichloromethane or a planetary ball mill. Diffusion experiments, P and Te-NMR, and mass spectroscopy revealed one of the reaction mechanisms at 60 °C. Catalytic amounts of alkylphosphanes in commercial [P ]Cl activate tellurium and form soluble phosphane tellurides, which react on the metal surface to solid telluride and the initial phosphane. In addition, a convenient method for the purification of [P ]Cl was developed.