Functionalization Studies of C₆₀ and Synthetic Approaches to Endohedral Metallofullerenes

Abstract

Two strategies aimed at the synthesis of endohedral metallofullerenes are presented. They have required the exploration of the surface chemistry of C₆₀ as well as the development of efficient syntheses of highly unsaturated acetylenic cyclophanes. These studies have led to the formation of the largest orifice on the framework of C₆₀ in the form of a cobalt(III) complex having the metal sitting on top of the opening. Further exploitation of the mechanisms involved in the formation of this cavity are discussed. In the second approach to metallofullerenes, highly unsaturated acetylenic cyclophanes have been designed to fold to fullerenes in a series of cascade reactions, either in the gas phase (mass spectroscopy, flash vacuum pyrolysis), or in solution (metal catalysis, radical-anion rearrangements). The origin of this second approach lies in the mechanism of gas-phase coalescence of polyynes during fullerene formation in the graphite evaporation method. Endohedral metal complexes of C₆₀ are expected to have interesting and diverse properties perhaps as rich as those of C₆₀ and other empty fullerenes.