Halogen bonds and metal bonds involving superalkalies M2OCN/M2NCO (M=Li, Na) complexes

A new type of halogen bond formed by supermetals or superalkalies with dihalogen molecules was analyzed by means of ab initio at the MP2/aug-cc-pVTZ level. The results reveal that the two configurations are found in the complexes M2OCN/M2NCO with dihalogen molecule, i.e., a linear structure made stable by halogen bond and a curved structure made stable by the cooperation of halogen bond and metal bond. The interaction energies and the NBO analysis indicate that the curved structures are more stable than the linear structures. To provide further insight into the nature of the intermolecular interaction, energy decomposition analysis was carried out, which implies that the electrostatic energy is the major source of the attraction for most complexes, except for Li2NCO/Na2NCOF2 where the main contribution is dispersion energy. In addition, atoms in molecules and molecular electrostatic potential were also used to probe halogen bonding and metal bonding strength. RDG graphical analysis reveals the spatial location and the strength of the weak interactions.