The Impact of the Solvent Dielectric Constant on A←NH₃Dative Bond Depends on the Nature of the Lewis Electron‐Pair Systems

Abstract

The present work aims to determine to what extent the value of the dielectric constant of the solvent can influence the dative bond in Lewis electron pair bonding systems. For this purpose, two different systems, namely H3B←NH3 and {Zn←(NH3)}2+, were studied in selected solvents with significantly different dielectric constants. Based on the results from state‐of‐the‐art computational methods using DFT, constrained DFT, energy decomposition analyses, solvent accessible surface area, and charge transfer calculations, we found that the stability of the neutral H3B←NH3 system increases with increasing solvent polarity. In contrast, the opposite trend is observed for the positively charged {Zn←(NH3)}2+. The observed changes are attributed to different charge redistributions in neutral and charged complexes, which are reflected by a different response to the solvent and are quantified by changes in solvation energies.

Trends in the stability of covalent dative bonds with variable solvent polarity depend on the charge transfer in the Lewis electron-pair system

“…Previously, we studied complexes with covalent dative bonds in both neutral and charged systems and observed varying stability trends in solvents as the dielectric constants of the solvents changed. 5–12 We have shown that the stability of DB in neutral complexes increases systematically with increasing solvent polarity. 5–10 However, the opposite trend is observed for DB in charged coordinate complexes.…”

The Stability of Hydrogen‐Bonded Ion‐Pair Complex Unexpectedly Increases with Increasing Solvent Polarity

“…(ZnÀ NH 3 ) 2 + , show the opposite effect. [12,13] This can be ascribed to solvation energies, which contribute to stabilization in the former case and induce destabilization in the latter. On the contrary, solvation affects the stability of most noncovalent complexes to only a small extent, including most hydrogen-bonded complexes.…”

The Stability of Hydrogen‐Bonded Ion‐Pair Complex Unexpectedly Increases with Increasing Solvent Polarity

“…NH 3 −BH 3 , are more stable in polar solvents, charged complexes, e.g. (Zn−NH 3 ) 2+ , show the opposite effect [12,13] . This can be ascribed to solvation energies, which contribute to stabilization in the former case and induce destabilization in the latter.…”