Sequentially condensing C2H4 and B2Br4 into a reactor in inert atmosphere, slow warming to ambient temp., stirring for 3 days.; Removing of volatiles in vac. at 0°C.;

hydrogen; boron tribromide react. of HBBr2 (in mixt. with H2 and BBr3) with acetylene at room temp.;

Sequentially condensing Cl4B2C2H4 and BBr3 into a reactor in inert atmosphere, stirring (0°C, 72 h).; Removing of volatiles in vac. at 0°C.;