tert.-butyl lithium in hexane byproducts: LiF; dropping a soln. of t-butyl lithium in n-hexane to a soln. of 2,4,6-tri-t-butylphenyl-fluoro-(phenylamino)borane in n-hexane under N2 at -20°C and allowing to stand overnight; removal of the solvent under reduced pressure and subliming the iminoborane from the residue in an oil pump vacuum, elem. anal.;