Chlorination-Promoted Skeletal Transformations in Isolated-Pentagon Rule (IPR) Isomers of Fullerene C₈₆ to Non-IPR Chloro- and Trifluoromethyl Derivatives

Fullerene C-86 contains two isomers obeying the Isolated-Pentagon Rule (IPR), C-S-C-86(16) and C-2-C-86(17). Both isomers undergo unprecedented skeletal transformations at high-temperature (400 degrees C) chlorination with SbCl5. One-step Stone-Wales rearrangement (SWR) in C-86(17) results in the pentagon-fused C-#63614(86) cage found in the structure of (C86Cl24)-C-#63614. CF3 derivatives with the same cage, two isomers of C-#63614(86)(CF3)(18) and C-#63614(86)(CF3)(18)O-2, were obtained by high-temperature trifluoromethylation of the chlorination products with CF3I, followed by HPLC separation. The skeletal transformation of C-86(16) proceeds via two SWRs under the formation of a C-#63624(86) cage with one fused-pentagon pair found in the structure of C-#63624(86)(CF3)(18). The addition patterns in skeletally transformed molecules are discussed in detail, disclosing the influence of the pentagon fusions, isolated C=C bonds, and benzenoid rings on the stability of the molecules with non-IPR C-86 cages. The chlorination-promoted SWRs in C-86 isomers have been observed for the first time, which contribute a lot to the understanding of skeletal transformations in fullerenes.