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, M3N@Ih‐C80 (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 Sc3N@Ih‐C80. Two isomeric Sc3N@Ih‐C80 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 Lu3N@Ih‐C80 cation, however, only a [6,6]‐open adduct was obtained. Density functional theory (DFT) calculations indicated that the oxidized M3N@Ih‐C80 was much more reactive than the neutral compound upon addition of the diethyl bromomalonate anion. The Bingel–Hirsch reaction of M3N@Ih‐C80 cations occurred by means of an unusual outer‐sphere single‐electron transfer (SET) process from the diethyl bromomalonate anion to the stable intermediate [M3N@C80(C2H5COO)2CBr].. Remarkably, the diethyl bromomalonate anion was found to act as both a nucleophile and an electron donor. The chemistry of cationic forms of clusterfullerenes is explored in terms of formation, reactivity and regioselectivity. M3N@Ih‐C80 (M=Sc or Lu) cations were generated by both electrochemical and chemical oxidation. The as‐obtained cations successfully undergo the typical Bingel–Hirsch reaction that fails with neutral Sc3N@Ih‐C80. The reaction of the cations occurs by means of an unusual outer‐sphere single‐electron transfer process.