Pyrazole‐Organoboranes, VI. Monomeric and Dimeric 9‐Pyrazolyl‐9‐borabicyclo[3.3.1]nonanes

Bis(9 H ‐9‐borabicyclo[3.3.1]nonane) (9H‐9‐BBN) 2 reacts with pyrazole ( Pz ) and its 4‐bromo, 3‐methyl, 3‐phenyl, 3,5‐dimethyl, 3‐methyl‐5‐phenyl, 3,5‐diphenyl, 3,5‐di‐ ert ‐butyl, 3,5‐diadamantyl, 3,5‐di‐ tert ‐butyl‐ 4 ‐methyl, and 3,5‐di‐ tert ‐butyl‐4‐ethyl derivatives [ brPz, mPz, pPz, m 2 Pz, mpPz, p 2 Pz, (tb) 2 Pz, (ad) 2 Pz, (tb) 2 mPz , and (tb) 2 mPz , and (tb) 2 ePz , respectively] to give the 9‐pyrazolyl‐9‐borabicyclo[3.3.1]nonanes with the dimeric structure (1) 2 – (3) 2 (X‐ray, NMR, and MS analysis), and 4 – 11 with monomeric structures (X‐ray, NMR, MS).