The hydroboration of benzo-, toluo-, p-methoxybenzo-, or pivalonitriles with bis(9-borabicyclo[3.3.1]nonane)2 (9H-9-BBN)2 affords the corresponding 9-aldimino-9-borabicyclo[3.3.1]nonanes (I) in about 80% yields. Compds. I (R = Ph, CMe3) readily react with and excess of (9H-9-BBN)2 to form the 1:1 adducts II contg. a NB2H four-membered ring (x-ray structure of II, R = Ph was obtained). The adducts II are thermally stable. II, R = Ph, is converted to benzylbis(1,5-cyclooctanediylboryl)amine only after 48 h at reflux in mesitylene. Compds. I are stable towards strong N-bases. I, R = CMe3 reacts with Et2O.BF3 to form 9-fluoro-9-borabicyclo[3.3.1]nonane and the 1:1 cyclic adduct III from (2,2-dimethylpropylideneamino)difluoroborane and I (R = CMe3).