Reactions of Fullerenes with Reactive Methylene Organophosphorus Reagents:  Efficient Synthesis of Organophosphorus Group Substituted C₆₀ and C₇₀ Derivatives

Treatment of C70 with cycloalkylaminomethylenebisphosphonates in the presence of NaH gave corresponding C70 dimers 1 in good yield, while the methanofullerenes, C70>CH(PO3Et2) (3) and C70>C(PO3Et2)2 (4) or C60>CH(PO3Et2) (5) and C60>C(PO3Et2)2 (6), were obtained, respectively, by the reaction of C70 or C60 with tetraethyl methylenediphosphonate in the presence of NaH. Diethyl cyanomethylphosphonate reacted with C60 or C70 under similar conditions to afford C60>C(PO3Et2)CN (7) and C70>C(PO3Et2)CN (8). Furthermore, the presence of weak electronic interactions between two fullerene cages of fullerene dimers was demonstrated by cyclic voltammetry. A radical mechanism was proposed for the formation of the fullerene derivatives on the basis of the ESR studies.