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

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 oC) chlorination of IPR C60 with SbCl5 or SbCl5/SbCl3 mixtures predominantly gives non-IPR C60Cln compounds via Stone-Wales rearrangements, but the present study further reveals non-classical C58Cln 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.