The reaction of dimethyl acetylenedicarboxylate (DMAD) with C(60) in the presence of hexamethylphosphorous triamide (HMPT) or hexaethylphosphorus triamide (HEPT) results in fullerene derivatives incorporating HMPT or HEPT ylides. The ylide derivatives exhibit unusual electronic absorptions in the visible region (435-660 nm), likely due to the presence of the ylide moiety. Electrochemical studies revealed that the first reductive potential of these compounds was more negative relative to those of both C(60) (DeltaE = 130 mV) and a simple Bingel adduct (DeltaE = 90 mV). A phosphoramidate side product, which resulted from the addition of HMPT or HEPT to C(60) followed by hydrolysis, exhibited a featureless absorption spectrum in the visible region and a more negative first reductive potential (DeltaE = 70 mV) relative to that of C(60).

Organophosphanes promote the [3+2] cycloaddition reactions of dialkyl (E)‐hex‐2‐en‐4‐ynedioates and [60]fullerene, giving a series of cyclopenteno‐fullerenes 3a–k bearing phosphorus ylides. This cycloaddition reaction is initiated by the attack of nucleophilic phosphanes at the α(δ′)‐C atom of the dialkyl (E)‐hex‐2‐en‐4‐ynedioate, which generates a 1,3‐dipolar species. These 1,3‐dipoles then react with C60 followed by intramolecular cyclization to give cyclopenteno‐fullerenes in moderate‐to‐good yields. In a cyclic voltmmetry study, these novel fullerenes show a larger cathodic shift in their first reduction potential relative to [6,6]phenyl‐C61 methyl butyrate, which indicates that these new derivatives possess higher LUMO energy levels.