Coordination of anions by noncovalently bonded σ-hole ligands

Research on σ-hole interactions that include halogen, chalcogen, pnicogen, and tetrel bonding has been accelerating in recent years. These cousins of the H-bond have many similar properties, including geometric preferences and energetics. Most of the work to date has focused on neutral complexes, with less known about these bonds to anions. This review summarizes the current state of knowledge about the complexes of anions with ligands that engage in these sorts of noncovalent bonds. Of particular interest are comparisons with H-bonds, and how the geometry of the fully coordinated complex varies as the number of surrounding ligands increases. A specific application of these ideas is explored in which these noncovalent bonds can be used to selectively bind certain anions in a multidentate arrangement, where a symbiotic interplay of experimental and computational methods has provided some useful insights.