Structural Chemistry of Pentagon-Fused C 82 Fullerene Derivatives #39173 C 82 (CF 3 ) 14,16,18 and #39173 C 82 Cl 28 .

High-temperature chlorination of the most stable Isolated-Pentagon-Rule (IPR) isomer of fullerene C 82 , C 2 -C 82 (3), invariably produces non-IPR #39173 C 82 Cl 28 , containing one pentagon-pentagon fusion in the carbon cage. High-temperature trifluoromethylation of #39173 C 82 Cl 28 followed by HPLC separation resulted in the isolation and structure elucidation of eight #39173 C 82 (CF 3 ) n ( n = 14, 16, 18) compounds. Structural chemistry of #39173 C 82 (CF 3 ) 14,16,18 and #39173 C 82 Cl 28 is characterized by the variation of the addition patterns in the region of a pentagon-pentagon fusion. The regiochemistry of CF 3 addition in the remaining cage region is similar to that of the known IPR C 82 (3)(CF 3 ) n compounds. Theoretical calculations revealed that #39173 C 82 (CF 3 ) n possess lower thermodynamic stability than isomeric IPR derivatives. High-temperature chlorination of fullerene C 82 with SbCl 5 followed by high-temperature trifluoromethylation of the chlorination product allowed the HPLC isolation and crystallographic structure elucidation of eight #39173 C 82 (CF 3 ) n ( n = 14, 16, 18) compounds. Structural chemistry of CF 3 and chloro derivatives with a unique, skeletally transformed pentagon-fused #39173 C 82 carbon cage is discussed in terms of the addition patterns and geometrical parameters of pentagon-pentagon fusions.