sodium in toluene 4 h; Heating;

boron tribromide in pentane T=-40°C; 3 h;

boron tribromide in diethyl ether; toluene T=-40 - 20°C;

in pentane all manipulations under N2; soln. of BBr3 added to stirred soln. of B compd. at -50- -40°C over period of 20 min, after 3 h allowed to warm to room temp.; solvent removed in vac., distd. in vac., elem. anal.;

in diethyl ether; toluene under N2, 1 equiv. of BBr3 in toluene was added to Et2O soln. of B-compd. at -20 °C in 20 min, stirring for 4 h then overnight at room temp.; solvent was removed in vac., residue was distilled at (70 and 100 °C, at 5E-2 and 6E-2 Torr, resp.) to give (C4H8N)2BBr and dibromo-diborane-compd. and monobromodiborane-compds., resp.;