sodium in toluene 4 h; Heating;

1: pentane; benzene 2: hexane View Scheme

in neat (no solvent) under N2, kept for 2 h at reflux; fractional distn.: B2(C4H8N)3(NMe2); elem. anal., residue dissolved in hexane, cooled to -78°C: B2(NC4H8)4;

NaK2.8 in toluene under N2; other products were also formed;

in hexane byproducts: NaCl, KCl; under N2, stirred overnight, refluxed for 1.5 h; filtered, volume reduced, cooled to -78°C; elem. anal.;

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

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.;