DFT study of chromium tricarbonyl complexes of coronene and kekulene

Abstract

A quantum chemical study of the mechanism and determination of the activation barriers of intramolecular η6,η6-inner-ring haptotropic rearrangements (IHR), consisting in moving a chromium tricarbonyl group Cr(CO)3 from one six-membered aromatic ring to another, are carried out using the density functional theory (DFT) for the respective η6-complexes of coronene I and kekulene II. The stationary states on the potential energy surface, determining the mechanism of η6,η6-IHR, have a lower hapticity, which is of interest for catalysis because of the possibility of coordinating an additional substrate and reagent around the transition metal during the rearrangement. The processes of η6,η6-IHR complexes I and II occur with similar energy barriers (ΔG≠ ≈ 20–25 kcal/mol) that are lower than the barriers (ΔG≠ ≈ 30 kcal/mol) of similar transformations previously calculated or measured for naphthalene complexes and a number of small polyaromatic hydrocarbons.