The Prominent Enhancing Effect of the Cation–π Interaction on the Halogen–Hydride Halogen Bond in M1⋅⋅⋅C6H5X⋅⋅⋅HM2

Abstract

We designed M(1)⋅⋅⋅C(6)H(5)X⋅⋅⋅HM(2) (M(1) =Li(+), Na(+); X=Cl, Br; M(2) =Li, Na, BeH, MgH) complexes to enhance halogen-hydride halogen bonding with a cation-π interaction. The interaction strength has been estimated mainly in terms of the binding distance and the interaction energy. The results show that halogen-hydride halogen bonding is strengthened greatly by a cation-π interaction. The interaction energy in the triads is two to six times as much as that in the dyads. The largest interaction energy is -8.31 kcal mol(-1) for the halogen bond in the Li(+)⋅⋅⋅C(6)H(5)Br⋅⋅⋅HNa complex. The nature of the cation, the halogen donor, and the metal hydride influence the nature of the halogen bond. The enhancement effect of Li(+) on the halogen bond is larger than that of Na(+). The halogen bond in the Cl donor has a greater enhancement than that in the Br one. The metal hydride imposes its effect in the order HBeH<HMgH<HNa<HLi for the Cl complex and HBeH<HMgH<HLi<HNa for the Br complex. The large cooperative energy indicates that there is a strong interplay between the halogen-hydride halogen bonding and the cation-π interaction. Natural bond orbital and energy decomposition analyses indicate that the electrostatic interaction plays a dominate role in enhancing halogen bonding by a cation-π interaction.