σ/π-Hole noble gas bonding interactions: Insights from theory and experiment

Abstract

Following the systematic nomenclature recommended by the IUPAC for other π,σ-hole interactions, a nobel gas (or aerogen) bond (NgB) is defined as the attractive interaction between an electron rich atom or group of atoms and any element of Group-18 acting as electron acceptor. Investigations on π,σ-hole interactions and their applications in crystal engineering, molecular recognition and catalysis have exponentially grown in recent years. For obvious reasons, investigations on noncovalent Ng bonding interactions are less abundant compared to their sisters (halogen, chalcogen, pnictogen and tetrel bonding, namely XB, ChB, PnB and TrB, respectively). In this review, we put into perspective the available theoretical and experimental investigations on σ-hole and π-hole interactions involving noble gas atoms. We describe a number of theoretical works revealing that NgB follows the typical behavior already described for XB, ChB, PnB and TrB, where stronger interactions occur moving the whole group down. A search the Cambridge Structural Database (CSD) and Inorganic Crystal Structure Database (ICSD) reveals that there are several X-ray structures of xenon derivatives where NgB interaction is crucial for the crystal packing stability. This taking is sub-divided into three sections subject to the oxidation state of xenon. The crystallographic search evidences that interactions between Xe and electron rich atoms are frequent and directional.