Metal‐Centered Noncovalent Interactions: A Comparative Insight into π‐Hole‐ and σ‐Hole‐Directed Bonds

This article investigates the π‐hole‐driven interactions of BeCl 2 , MgCl 2, and HgCl 2 , as well as the σ‐hole‐directed interactions of MoOF 4 and OsO 4 with substituted pyridines. Among the π‐hole complexes, the Be…N beryllium bond exhibits the highest binding strength, followed by Mg…N magnesium bond and Hg…N spodium bond, whereas within the σ‐hole complexes, the Mo…N wolfium bond is stronger than the Os…N osme bond. The overall binding energy (Δ E ) trend follows: BeCl 2 > MgCl 2 > MoOF 4 > HgCl 2 > OsO 4 , and shows a linear correlation with the deformation energy of the Lewis acids. AIM analysis reveals partial covalent character of all M…N interactions (M = metal), except MgCl 2 complexes, which are predominantly electrostatic in nature. Natural bond orbital (NBO) analysis indicates that although second‐order hyperconjugation energies correlate with Δ E within each class, they are not solely determinative; notably, despite significantly higher E 2 values corresponding to LP(N) → LP*(M) interaction in BeCl 2 relative to MgCl 2 complexes, the difference in Δ E remains marginal due to a larger opposing exchange contribution in BeCl 2 complexes. Furthermore, while σ ‐hole complexes are primarily governed by LP(N) → σ*(M–O) interactions, MoOF 4 uniquely exhibits an additional LP(N) → LP*(Mo) orbital interaction. The bond (MCl/MO) elongations and the corresponding vibrational redshifts show strong linear correlations with Δ E .