The dimerization of borane has been investigated with the
MNDO method. Three pathways have been studied by imposing
different symmetry restrictions: C2h symmetry, least-motion, and
with no symmetry at all. The activation energies of the three
pathways are 3.8, 31.5, and 2.7 kcal/mol, respectively. In view of
the known tendency of MNDO to yield high energy for transition
states, the low activation energy of the la\u27St pathway probably
means that the dimerization has no or a very small energy barrier.
Moreover, it turns out that C, symmetry is retained automatically
for this pathway
