How Many Pnicogen Bonds can be Formed to a Central Atom Simultaneously?

Rafał Wysokiński,Wiktor Zierkiewicz,Steve Scheiner,Mariusz Michalczyk

doi:10.1021/acs.jpca.0c00257

Abstract

A central ZF3 molecule (Z = P, As, Sb, Bi) is allowed to interact with a number of nucleophiles exemplified by NCH, NH3, and NC– anion. The Z···N pnicogen bond (ZB) to a single base grows stronger for heavier Z atom: P < A < Sb < Bi and follows the NCH < NH3 < NC– order for the three bases. The maximum number of ZBs depends on both the nature of the base and pnicogen atom. PF3 and AsF3 can pnicogen bond with only a single CN–; SbF3 and BiF3 can interact with two anions but only weakly. The weak NCH nucleophile can engage in a maximum of two ZBs, while three ZBs occur for NH3. The latter NH3 maximum can be extended to four ZBs but only for BiF3. The fourth ZB is somewhat longer and weaker than the others, and the entire (H3N)4···BiF3 complex relies partially on secondary interactions for its stability.

Highlights

In the years following its initial conception, the hydrogen bond (HB) has become one of the most important and far-reaching phenomena for both chemistry and biology.[1−8] Recent years have witnessed the growth of study of a set of parallel sorts of interactions, replacing the bridging proton of the HB by any set of other elements in the p-block of the periodic table
These electronegative elements are able to attract an electron donor by way of a region of depleted electron density on their periphery, which in turn are commonly referred to as σ- or πholes.[9−18] A good deal of work has addressed the factors that contribute to this bonding phenomenon, the strength of the interaction, and the subsidiary part played by monomer deformation, to amplify its role in biological systems, pharmacology, and technology.[1,2,19−30] For example, it is understood that these noncovalent bonds are stabilized by contributions from charge transfer, polarization, and dispersion, in addition to the electrostatic attraction
ZF3 can engage in two Z···N pnicogen bond (ZB) with NCH, but a third such base engages only weakly with the (CHNC−Na)p2·o··wZeFr3fual nnducnleootphviiale,abiZnBd.inIgtstoneZgFa3tibvey charge makes upwards of 20 kcal/mol, as much as 40 kcal/mol for Z = Bi

Summary

■ INTRODUCTION

In the years following its initial conception, the hydrogen bond (HB) has become one of the most important and far-reaching phenomena for both chemistry and biology.[1−8] Recent years have witnessed the growth of study of a set of parallel sorts of interactions, replacing the bridging proton of the HB by any set of other elements in the p-block of the periodic table These electronegative elements are able to attract an electron donor by way of a region of depleted electron density on their periphery, which in turn are commonly referred to as σ- or πholes.[9−18] A good deal of work has addressed the factors that contribute to this bonding phenomenon, the strength of the interaction, and the subsidiary part played by monomer deformation, to amplify its role in biological systems, pharmacology, and technology.[1,2,19−30] For example, it is understood that these noncovalent bonds are stabilized by contributions from charge transfer, polarization, and dispersion, in addition to the electrostatic attraction. The properties of each complex are monitored to follow changes occurring in each system upon each addition of another base unit

■ METHODS

■ RESULTS

■ DISCUSSION AND CONCLUSIONS

■ ACKNOWLEDGMENTS

Findings

■ REFERENCES