Ruthenophanes: Evaluating Cation−π Interactions in [Ru(η⁶‑C₁₆H₁₂R₄)(NH₃)₃]^2+/3+ Complexes. A Computational Insight

Abstract

The nature of cation−π interactions in a set of [Ru­(η⁶-C₁₆H₁₂R₄)­(NH₃)₃]²⁺³⁺ (R = F, CN, CH₃, and others), complexes was investigated with Su–Li energy decomposition analysis and the natural orbitals for chemical valence and the extended transition state method EDA-NOCV. The long-distance effects of electron-donating and electron-withdrawing substituents as well as protonation of the <i>ipso</i> carbon on the nature of cation−π interactions were investigated. Both energy decomposition analyses, Su–Li EDA and EDA-NOCV, are in total agreement, showing that the presence of electron-donating substituents such as CH₃, NH₂, and H₃CO tends to stabilize the ruthenium–arene interaction while electron-withdrawing substituents such as F, CN, and NO₂ tend to weaken such interactions. The electrostatic component of the ruthenium–arene interaction is the most affected by the substitution, despite the fact that the covalent character is much more significant than the electrostatic character. EDA-NOCV reveals that the most important orbital stabilization comes from donation and back-donation between the interacting fragments, while the σ density deformations present a moderate contribution to total orbital stabilization energy in ruthenium–arene interactions of complexes <b>1</b>–<b>8</b>