Chloro- and Trifluoromethyl Derivatives of a Pentagon-Fused\nC₆₀: ¹⁸¹⁰C₆₀Cl₂₄, ¹⁸¹⁰C₆₀Cl₂₀, and ¹⁸¹⁰C₆₀(CF₃)₁₄

Abstract

The\ncarbon cage of <i>I</i>_<i>h</i>-C₆₀, obeying the isolated-pentagon rule (IPR), can be\ntransformed to the non-IPR <i>D</i>_2<i>h</i>-¹⁸¹⁰C₆₀ cage via two successive Stone–Wales\nrearrangements in the course of high-temperature chlorination of C₆₀ with SbCl₅. Two chloro derivatives, <i>C</i>_2<i>v</i>-¹⁸¹⁰C₆₀Cl₂₄ and <i>C</i>_2<i>v</i>-¹⁸¹⁰C₆₀Cl₂₀, have been isolated by high-performance\nliquid chromatography (HPLC). High-temperature trifluoromethylation\nof the chlorination products with CF₃I, followed by HPLC\nseparation, afforded a non-IPR CF₃ derivative, <i>C</i>_<i>s</i>-¹⁸¹⁰C₆₀(CF₃)₁₄. Structural elucidation of the isolated\ncompounds revealed that all eight sites of pentagon–pentagon\nfusions on the carbon cage are preferentially occupied by Cl atoms\nor CF₃ groups. According to density functional theory calculations,\nchloro and CF₃ derivatives of ¹⁸¹⁰C₆₀ are more stable than the isomeric derivatives of ¹⁸⁰⁹C₆₀ or IPR ¹⁸¹²C₆₀, possessing respectively\nfour or no sites of pentagon fusion in their carbon cages.