Ruthenophanes: Evaluating cationπ interactions in [Ru(n ⁶-C₁₆H₁₂R₄)(NH₃) ₃]^2+/3+ complexes. A computational insight

The nature of cationπ interactions in a set of [Ru(?⁶-C ₁₆H₁₂R₄)(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 ipso carbon on the nature of cationπ 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 ? density deformations present a moderate contribution to total orbital stabilization energy in ruthenium-arene interactions of complexes 1-8.