hydrogen bromide in pentane prepn. of a suspn. of freshly prepared borane in anhyd. pentane under N2, cooling to 0°C while a slow stream of HBr is passed through under stirring, stopping of stirring and standing at 0°C for 2-3 h; transferring of pentane soln. by cannula, solvent removal in vac., viscous residue is solidified by standing, recrystn. from cold pentane;