Pnicogen and tetrel bonds—tetrahedral Lewis acid centres

Abstract

It is obvious and well known that the hydrogen bond plays a crucial role in numerous physical, chemical and biochemical processes. However, the significance of other interactions is also analysed in numerous studies. They are often compared with the hydrogen bond. The halogen bond is an example of such interaction that reveals characteristics occurring also for the hydrogen bond. The other interactions which are often classified as the σ-hole bonds or π-hole bonds possess characteristics typical for the hydrogen bond. The interactions of tetrahedral pnicogen and tetrel centres with Lewis bases are analysed here. The former ones may be labelled as the charge-assisted pnicogen bonds and classified as the σ-hole bonds. The latter ones labelled as the tetrel bonds are also classified as interactions between the σ-hole and the electron-rich region. Both these interactions are compared with the hydrogen bond. In the case of the hydrogen bond, the A–H...B, A–H...π and A–H...σ types of interactions are discussed in different studies where A–H is the proton-donating bond while B, π and σ label the kind of the proton acceptor: the mono-atomic Lewis base centre B, the π-electrons and the σ-electrons, respectively. The pnicogen centre, Z, in the charge-assisted pnicogen bonds may also interact with these electron-rich regions thus the Z...B, Z...π and Z...σ pnicogen bonds are known.