Ammonia - Trifluoroborane, A Lewis Base / Lewis Acid Complex

The N-atom in ammonia is sp3 hybridized and it remains so in the complex. On the other side, the B-atom in the free Lewis acid is sp2-hybridized and it becomes more sp3-hybridized in the complex. The staggered structure is more stable: eclipsed E(MP2) = -380.189902 a.u. and staggered E(MP2) = -380.191809 a.u.


Figure. The MP2(full)/6-31G* optimized structures of the Lewis acid / Lewis base complex formed between the Lewis base ammonia and the Lewis acid trifluoroborane. The ecliped structure is shown on the left and the staggered structure on the right.