in tetrahydrofuran dropping soln. of BH3*THF in THF to soln. of borane in THF at -78°C, under N2 or Ar; refluxing for 1 h; mechansim discussed;; removal of solvent in vac.; recrystn. from ether; 1. and 2. fraction product mixts., 3. fraction pure 9-borabicyclo(3.3.1)nonane, 4. fraction small amt. of pure (BH2P(tert-butyl)2)2; detn. by NMR;;