Fullerenes are spherical cage carbon molecules constructed from hexagons and exactly 12 pentagons. [1, 2] Theoretically, according to the so-called Isolated Pentagon Rule (IPR), [3] fullerenes with isolated pentagons are relatively stable and synthesizable. This same rule predicts that fullerenes with fused pentagons are too reactive to be isolated. IPR-violating fullerenes, however, have been reported to be stabilized by either encapsulation with metal atoms (or their carbide/ nitride clusters) [4,5] or external derivatization. [6a, 7] Fullerenes featuring fused pentagons have been characterized by computationally corroborated 13 C NMR spectroscopy. [6][7][8] Detailed information regarding their geometries and intermolecular interactions, however, requires single-crystal X-ray characterization, as in the case of Sc 3 N@C 68 . [9] The crystal structures of two double-fused-pentagon endohedral metallofullerenes, namely La@C 72 (C 6 H 3 Cl 2 ) [10] and Tb 3 N@C 84 , [11] have also been determined. Highly accurate structural parameters established by X-ray crystallography are rare for exohedral derivatives of IPR-violating fullerenes. Prinzbach et al., for example, have recently reported the crystal structures of polybrominated dodecahedrane, [12] which is the smallest IPR-violating fullerene derivative known to date. Herein we report two crystal structures of IPR-violating fullerenes (C 50 (no. 271) and C 64 (no. 1911)) [2,13] stabilized by exohedral chlorination. The former is the smallest fullerene [