The ionization potentials (IP) and electron affinities (EA) for a number of hydrogenated and fluorinated derivatives of C60 and C70 have been determined using the charge exchange “bracketing” technique. Samples of C60Hx and C70Hy were prepared by direct solid phase hydrogenation (x=2-18, y=2-30) or platinum oxide catalytic hydrogen reduction (x=36, y=36). The IP's for C60H2-18 are between 6.75 and 7.53 eV for even x<10 and lower than 6.75 for odd x<10. The EAs for C60F44,46,48, and C70F52,54 were “bracketed” to be 4.0 ± 0.25 eV. The highly fluorinated chiral C3h molecule C60F48 was observed to directly attach two electrons in the gas phase to produce C60F48
2- and C60F46
2− + F2−. Studies of the metastable decompositions and collision-induced dissociation of C60F48
2− showed fluorine atom and F2 loss, but no loss of an electron. In addition, the C60F48,46,44
2− dianions do not charge exchange with molecules possessing high electron affinities, including the neutral parent compound, C60F48
2− (EA = 4.06 eV). The remarkable stability of C60F48
2− to the removal of an excess electron is attributed to a long-range Coulomb barrier which is built from the bound state for the two electrons near the molecule and the electron-electron Coulomb repulsion between the two at large distance.