Amine borane Dissociation energy

The cubic crystalline form of boron nitride has a diamond-like structure, each boron atom is bonded to four nitrogen atoms at a bond distance of 156 pm. The mean NB bond energy calculated from the energy of atomization is 321 kJ mol i.e. more than 2.5 times larger than the NB bond dissociation energy of amine borane. We conclude that the NB bond in amine borane is not only unusually long, but also unexpectedly weak. 

N- -B bond distances and dissociation energies in substituted amine borane complexes... 

Table 16.1. Dissociation energies (at 298 K) and N — B bond distances in gaseous substituted amine borane complexes.

Since the N-B bond in amine borane is so weak, it is very sensitive to substitution effects as indicated by the following gas-phase dissociation energies ... 

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