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.