With bromine in tetrachloromethane dropwise addn. of Br2 in CCl4 to a stirred soln. of Ge-compd. at 0°C under N2, stirring for 1 h, then warming to room temp.; evapn. to dryness, recrystn. from hexane or liquid chromy. by medium pressure with hexane/ethylacetate, elem. anal.;