Chemical Reactions of Cationic Metallofullerenes: An Alternative Route for Exohedral Functionalization

The chemistry of cationic forms of clusterfullerenes remain less explored than that of the corresponding neutral or anionic species. In the present work, M 3 N@ I h ‐C 80 (M=Sc or Lu) cations were generated by both electrochemical and chemical oxidation methods. The as‐obtained cations successfully underwent the typical Bingel–Hirsch reaction that fails with neutral Sc 3 N@ I h ‐C 80 . Two isomeric Sc 3 N@ I h ‐C 80 cation derivatives, [5,6]‐open and [6,6]‐open adducts, were synthesized, and the former has never been prepared by means of a Bingel–Hirsch reaction with neutral clusterfullerenes. In the case of the Lu 3 N@ I h ‐C 80 cation, however, only a [6,6]‐open adduct was obtained. Density functional theory (DFT) calculations indicated that the oxidized M 3 N@ I h ‐C 80 was much more reactive than the neutral compound upon addition of the diethyl bromomalonate anion. The Bingel–Hirsch reaction of M 3 N@ I h ‐C 80 cations occurred by means of an unusual outer‐sphere single‐electron transfer (SET) process from the diethyl bromomalonate anion to the stable intermediate [M 3 N@C 80 (C 2 H 5 COO) 2 CBr] . . Remarkably, the diethyl bromomalonate anion was found to act as both a nucleophile and an electron donor.