High and low barriers to haptotropic shifts across polycyclic surfaces: the relevance of aromatic character during the migration process

Haptotropic shifts of ML n fragments, such as (C 5 H 5 )Fe, Mn(CO) 3 or Cr(CO) 3 , across polycyclic carbon frameworks generally follow a ‘non least-motion’ trajectory. In the absence of a definitive and unifying rationale for the preference of migratory pathways documented in previous experimental studies, a theoretical explanation has been sought. The potential energy surfaces (PES) for the migrations of organometallic fragments over the …