Regular/abnormal variation in the strength and nature of the halogen bond between H 2 Te and the dihalogens: Prominent effect of methyl substituents

The halogen‐bonded complexes between H 2 Te/Me 2 Te and the dihalogen molecules XY (XY = F 2 , Cl 2 , Br 2 , I 2 , ClF, ClBr, BrF, BrCl, BrI, IF, ICl, IBr) have been studied to investigate the dependence of its strength and nature on the halogen donor X and its adjoining atom Y, as well as the methyl groups in the electron donor. The interaction energy varies between −1.7 and − 43.5 kcal/mol, indicating that the Te atom in H 2 Te/Me 2 Te has a strong affinity for the dihalogen molecules. For the H 2 Te‐XY complex, the halogen bond is stronger for the heavier halogen donor X atom and the strong electron‐withdrawing group Y. However, for Me 2 Te‐XY, the halogen bond is stronger for the lighter halogen donor X atom. The H 2 Te/Me 2 Te‐F 2 complex has the largest interaction energy, although the σ‐hole on F 2 is the smallest in magnitude. In most of the complexes, the electrostatic and polarization contributions to the binding strength are similar in magnitude. However, for H 2 Te/Me 2 Te‐F 2 , the polarization contribution is much larger than the electrostatic contribution, with a significant contribution from charge transfer.