Understanding the Reactivity of Endohedral Metallofullerenes: C78 versus Sc3N@C78

The physical factors behind the reduced Diels-Alder reactivity of the Sc3N@C-78 metallofullerene as compared with free C-78 have been investigated in detail by means of computational tools. To this end, the reactions between 1,3-butadiene and free C-78 and endohedral Sc3N@C-78 have been analysed in terms of regioselectivity and reactivity by using the activation strain model of reactivity in combination with the energy decomposition analysis method. Additional factors such as the molecular orbital overlap or the aromaticity of the corresponding transition states have been also explored. Our results indicate that the lower reactivity of the metallofullerene finds its origin mainly in the less stabilizing interaction between the deformed reactants along the reaction coordinate induced by the triscandium nitride moiety.