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).