Unveiling the Potential of Haloalkenes as Electron Density Acceptors.

We report herein, by means of structural and computational analyses, a comprehensive study of the capability of differently substituted haloalkenes to behave as electron density acceptors in noncovalent interactions. The nature of these interactions between haloalkenes and Lewis bases highly depends on the number and nature of the halogen atoms bound to the carbon-carbon double bond. When hydrogen bonds, which generally dominate for mono- and dihaloalkenes, cannot be formed, we observe the establishment of attractive interactions in which an sp carbon atom, belonging to an acyclic C=C double bond, plays the role of the Lewis acid via its π* antibonding orbital.