Fluorinated fullerenes: Synthesis and characterization

The existence of the fully fluorinated fullerene, C 60 F 60 , is still subject to controversy. Mass spectrometric evidence shows that it exists, albeit in trace amounts five orders of magnitude in concentration below the most abundant C 60 F 40‐42 . Generally, mixtures of C 60 F n are obtained where n ranges from 30 to 52, depending on fluorinating conditions. The species with n = 36 is particularly stable. Attempts to increase n by use of the strongly fluorinating halogen fluorides, ClF 3 or BrF 5 , have led to products C 60 F X X y O z (X = Br or Cl), where the origin of the oxygen is probably hydrolysis during analysis. Fluorinated C 60 crystallizes as a mixture of hexagonal close packed (40%) and face‐centered cubic (60%) phases. X‐ray analysis yields an average C‐F bond length of 1.49A. Fluorination of C 70 leads to mixtures with maximum average stoichiometries of C 70 F 52 .