Pentavalent pnictogen bonds involving triarylpnictogen catecholates as strong Lewis acids: Crystallographic survey and theoretical analysis

As a novel class of Lewis acids, triarylpnictogen(V) catecholate compounds have attracted increasing attention in anion binding and transport, supramolecular chemistry, and organocatalysis. In this work, pentavalent pnictogen bonds (PnBs) formed by these compounds and chloride ion were investigated in detail via the combination of crystallographic data analysis and quantum chemical calculations. Owing to the much shorter intermolecular distances and the considerably more negative binding energies, pentavalent PnBs show a remarkably enhanced strength compared with conventional trivalent PnBs, leading to a greater degree of covalency for hypervalent PnBs. Energy decomposition analysis revealed that both the electrostatic and the orbital terms contribute significantly to the attraction of pentavalent PnBs, while the Pauli repulsion term plays an important role in rationalizing the observed Lewis acidic tendency of pnictogens. In addition, the influence of different substituents either in the phenyl rings or in the catecholate group was also examined for these interactions.