Transanular Interactions in Difunctional Medium Rings, 5. Spectroscopic Investigations of Bicyclic Boraamines

The endo‐7‐[(dialkylamino)methyl]‐3‐borabicyclo[3.3.1]nonanes 1 and 2 have been synthesized and their intramolecular complex formation of the corresponding 2‐azonia‐1‐boratatricyclo[4.3.1.14,8]undecanes 3 and 4 has been studied in the gas phase by UV photoelectron spectroscopy and in solution by 11‐NMR spectroscopy. Deviations of the characteristic spectral features from those of the monofunctional bicyclic boranes 5 and amines 6 and 7 indicate that in the gas phase the (dimethylamino)boranes with a B‐alkyl substituent adopt the tricyclic form 3a–c whereas the diethylamino and the B‐methoxy derivatives 1e and 2 prefer the bicyclic structure. In solution some deviations from this behavior are observed.