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 quan tum chemical simulation. A variational transition-state theory model implem enting an ion-quadrupole plus ion-induced dipole potential is employed in t he modeling of the kinetic data for the collision-induced dissociation of t hese complexes. For Cr+, a global potential is generated for its interactio n with benzene and radiative association experiments are also modeled. impl ementation of this potential in the transition-state analyses indicates onl y minor anharmonicity effects for the complex state density near the dissoc iation threshold and negligible deviation from the long-range potential-bas ed predictions for the transition-state partition functions. Theoretical op timized geometries, binding energies, and vibrational frequencies are deter mined 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-shap ed distortions of the benzene ligand. The quantum chemical and kinetic mode ling based estimates for the binding energies are in reasonable agreement.