Theory and modeling of the binding in cationic transition-metal-benzene complexes

Binding energies are estimated for the complexes of benzene with the first-row transition-metal ions (M+ = Ti+-Cu+) via both kinetic modeling and quantum chemical simulation. A variational transition-state theory model implementing an ion-quadrupole plus ion-induced dipole potential is employed in the modeling of the kinetic data for the collision-induced dissociation of these complexes. For Cr+, a global potential is generated for its interaction with benzene and radiative association experiments are also modeled. implementation of this potential in the transition-state analyses indicates only minor anharmonicity effects for the complex state density near the dissociation threshold and negligible deviation from the long-range potential-based predictions for the transition-state partition functions. Theoretical optimized geometries, binding energies, and vibrational frequencies are determined with the B3LYP (Becke-3 Lee-Yang-Parr) density functional. The V+, Ni+, and Fe+ complexes are found to have modest Jahn-Teller-induced boat-shaped distortions of the benzene ligand. The quantum chemical and kinetic modeling based estimates for the binding energies are in reasonable agreement.