Reactivities of copper-germanium alloys in the direct synthesis of dimethyldichlorogermane

Abstract

The activities of the single phase alloys a (Ge in Cu), ζ (Cu 5Ge), and ϵ (Cu 3Ge) in the reaction with methyl chloride to form methylchlorogermanes were measured at 426.7 °C. The alloys displayed essentially the same reactivity when compared on the basis of the same number of germanium atoms exposed to methyl chloride. Selectivity for (CH 3) 2GeCl 2 approached 100% at 0% conversion of germanium, thus supporting the ionic mechanism of Voorhoeve. The extent of cracking of methyl chloride could be correlated with the fraction of the surface estimated to consist of copper atoms not involved in the synthesis of methylchlorogermanes. Removal of copper from thin surface layers, probably as CuCl, was confirmed by X-ray analysis in the case of the α phase. Mechanical mixtures of alloys and free germanium showed greatly enhanced reactivities which could be explained only by the creation of additional reaction sites on the surfaces of the free germanium particles.