boron trichloride in hexane T=20°C; 2 h;

in hexane byproducts: (Me2N)BCl2; under N2, standard Schlenk techniques; bis(dimethylamino)borane dissolved in hexane at -78°C; soln. of BCl3 (2 equiv.) in hexane added dropwise within 10 min; warmed to room temp. within 2 h; stirred overnight; volatiles removed under vac.; sublimed (60°C, 0.001 Torr) into cold tube (-78°C); elem. anal.;