Electrochemical Studies of the Protonation of Ca - and Ca 2 -

Cyclic voltammetric reduction of c60 to the radical anion, c60-, is unaffected by the presence of weak proton donors in o-dichlorobenzene, indicating that the monoanion is a weak base. Further reduction to the dianion results in a drastic increase in basicity, and an estimate of the acidity of the conjugate acid, C60H-, is obtained. Bulk electrolysis studies allow further characterization of the monoanion properties, including an estimate of the acidity of C60H' relative to triflic acid. The dianion can be titrated in acetonitrile by triflic acid to form an orange solution that FAB mass spectral analysis indicates is C60HZ. Spectrophotometric titration of the anions reveals two new, distinct species, which we attribute to C60H' and C60H-,