Dual function of the boron center of BH(CO)2/BH(N2)2 in halogen- and triel-bonded complexes with hypervalent halogens.

The complexes between BH(CO)2/BH(N2)2 and XF3/XF5 are stabilized by a halogen bond and a triel bond. The MEP analyses of BH(CO)2/BH(N2)2 indicate that there are both a region with negative MEPs on the B atom in the vertical direction of the molecular plane and a σ-hole at the B-H bond end. Therefore, the boron atom in BH(CO)2/BH(N2)2 plays a dual role of a Lewis base and an acid in the halogen bond and triel bond, respectively. The halogen and triel bonds are stronger in order of IF3< BrF3< ClF3, IF5< BrF5< ClF5, and BH(CO)2< BH(N2)2 in most complexes. These complexes have large stability since the interaction energy varies from -5 to -115 kcal/mol. The halogen bond belongs to a covalent interaction or a partially covalent interaction in most complexes. The subsystems in these complexes have prominent deformation, accompanied with big charge transfer and large polarization.