Fluorinated elements of Group 15 as pnictogen bond donor sites

Abstract

The presence of fluorine atom(s) in a molecule makes the σ-hole potentials of surrounding atoms more positive and thus increases their tendencies to interact attractively with nucleophiles. This review shows that in the crystal structures of fluorinated derivatives of the Group 15 atoms, close contacts between Group 15 atoms and negative sites (e.g. lone pair possessing atoms and anions) are quite common. These close contacts are taken as indications of attractive interactions. The collection of single crystal X-ray structures analysed in this paper demonstrates that the ability of fluorinated atoms of Group 15 to work as electrophilic sites, namely to function as pnictogen bond donors, is fairly general. The directionalities and separations of these pninctogen bonds are convincing experimental evidences that linking a fluorine to a pnictogen atom increases its electrophilicity to the point that pnictogen bonding formation may become a determinant of the lattice structures in crystalline solids. Pnictogen bonding formation may become an heuristic principle for predicting some of the short contacts that are present in the crystal structures of compounds containing fluorinated atoms of Group 15, particularly when polyfluorinated. Pnictogen derivatives containing other moieties may also work as effective electrophilic sites and a convenient design of the used tectons may allow pnictogen bond to become a general and reliable tool in crystal engineering.