Kinetic stability of metallofullerenes as predicted by the bond resonance energy model

Abstract

Endohedral metallofullerenes consist of a negatively charged fullerene cage and one or more metal cations within it. The minimum bond resonance energy (min BRE) proved to be a useful index for predicting the degree of kinetic stability of metallofullerenes. It was found that all metallofullerenes so far extracted and structurally identified have a negatively charged carbon cage with a min BRE> − 0.100 ∣β∣. All isolable or extractable metallofullerenes are then presumed to be not only thermodynamically but also kinetically stable in this sense. It is noteworthy that some of the carbon cages employed for the formation of metallofullerenes are kinetically very unstable when they are deprived of negative charge. All molecular anions of C₈₄ with − 1 to − 6 formal charges are predicted to be kinetically stable with a min BRE> − 0.100 ∣β∣.