Strategies to stabilize exohedral η⁵- and η⁶-fullerene transition metal organometallic complexes: a molecular orbital treatment

Abstract

Transition metal fragments are designed to overcome the unfavourable interaction arising from the splayed-out π-orbitals of the five-and six-membered rings of C₆₀ in complex formation. Semiemprical studies at the PM3(tm) level on a series of C₆₀MC_nH_n complexes suggest that, with the appropriate transition metal fragment, it is possible to stabilize η⁶-complexes of C₆₀. Isodesmic equations of the type C_mH_mMC_nH_n + C₆₀→ C₆₀MC_nH_n + C_mH_m indicate that C₃H₃Co and C₃H₃Rh are ideal fragments in stabilizing η⁶-C₆₀ complexes. In comparison, η⁵-complexes are less favourable; structural modifications such as those in the recently synthesized C₆₀Ph₅^- should readily help η⁵-bonding.