Fluxional behavior of group 6 and 7 metal borane complexes was investigated with use of density functional theory (DFT). Site exchange of BH hydrogen atoms of the borane ligand BH3 center dot L or B2H4 center dot 2PMe(3) proceeds via a transition state in which the borane ligand interacts with metal with a bidentate fashion. Calculated values of the activation energy were in good agreement with experimentally observed barriers.