Chlorination-Supported Shrinkage of C60 Fullerene to Non-classical C58 Cages.

Abstract

We provide important novel insights into skeletal transformations of fullerene by reporting new cases of cage shrinkage in the most abundant C₆₀ fullerene via a C₂ loss. High-temperature (400-500 °C) chlorination of IPR C₆₀ with SbCl₅ or SbCl₅/SbCl₃ mixtures predominantly gives non-IPR C₆₀Cl_n compounds via Stone-Wales rearrangements, but the present study further reveals non-classical C₅₈Cl_n chlorofullerenes as by-products. The new C₅₈(NC1)Cl₂₀ and C₅₈(NC1)Cl₂₄ chlorides have been isolated by air-free HPLC and structurally characterized by X-ray crystallography. Their non-classical carbon cages feature one heptagon, two pairs of fused pentagons, one triple-pentagon junction, and one quartet of sequentially fused pentagons. However, the chlorination patterns and molecular shapes of C₅₈(NC1)Cl₂₀ and C₅₈(NC1)Cl₂₄ are essentially different. We propose the likely multistep transformation pathways toward the new compounds and further report the chlorination-promoted formation of chlorofullerenes with still smaller fullerene cages.