Low Temperature Activation of Tellurium and Resource-Efficient Synthesis of AuTe₂ and Ag₂Te in Ionic Liquids

The low temperature syntheses of AuTe2 and Ag2Te starting from the elements were investigated in the ionic liquids (ILs) [BMIm]X and [P66614]Z ([BMIm]+=1-butyl-3-methylimidazolium; X = Cl, [HSO4]−, [P66614]+ = trihexyltetradecylphosphonium; Z = Cl−, Br−, dicyanamide [DCA]−, bis(trifluoromethylsulfonyl)imide [NTf2]−, 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 [P66614]Cl is the most promising candidate for the single phase synthesis of AuTe2 at 200 °C. Ag2Te 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 [P66614]Cl in dichloromethane or a planetary ball mill. Diffusion experiments, 31P and 125Te-NMR, and mass spectroscopy revealed one of the reaction mechanisms at 60 °C. Catalytic amounts of alkylphosphanes in commercial [P66614]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 [P66614]Cl was developed. © 2020 The Authors. Published by Wiley-VCH Gmb