Coordination and Haptotropic Migration of Cr(CO)₃ in Polycyclic Aromatic Hydrocarbons:  The Effect of the Size and the Curvature of the Substrate

In this work, we study the reaction mechanism of the tricarbonylchromium complex haptotropic rearrangement between two six-membered rings arranged like in naphthalene of four polycyclic aromatic hydrocarbons (PAHs). It has been found that the reaction mechanism of this haptotropic migration can either occur in a single step or stepwise depending on the interaction between the orbitals of the Cr(CO)₃ and the PAH fragments. Our results show that the size of the cyclic system favors the metal migration whereas the curvature of the organic substrate tends to slow down the rearrangement. We discuss the key factors that help to explain this behavior through orbital and energy decomposition analysis.