Organic Approaches to Endohedral Metallofullerenes: Cracking Open or Zipping Up Carbon Shells?

We have been investigating the synthesis of endohedral metallofullerenes since we successfully opened an orifice on the framework of C 60 in the form of a cobalt complex having the metal sitting on top of the opening. A second approach aims at the synthesis of spherically‐shaped acetylenic macrocycles, which are expected to rearrange to endohedral metal complexes of fullerenes in a controlled process analogous to the gas‐phase coalescence of mono‐ and polycyclic polyynes during fullerene formation by the graphite evaporation method. Since the potential benefits from obtaining endohedral metal complexes of C 60 are enormous, both approaches are being actively pursued in our group.