9-Fluoro-9-borabicyclo[3.3.1]nonane (I), prepd. from bis(9-borabicyclo[3.3.1]nonane) with SbF3 or SbF5 in high yields, is characterized by IR, mass, and multinuclear NMR spectroscopy. Pure I in soln. has a small 11B-NMR singlet signal in contrast to the freshly prepd. I with the normal JFB-split 11B resonance. The x-ray structure anal. of I with 3 differently bonded mols. in the cell shows a monomer and a dimer of I with BFB coordination bond. Some Lewis base adducts of I are prepd., the others were characterized by 11B-NMR spectra.