Identifying a Needle in a Haystack: Isolation and Structural Characterization of Er2C94 as the Carbide Er2C2@D3(85)‐C92

: A method has been developed for isolating a pure sample of Er2 C94 from the myriad of fullerenes and endohedral fullerenes that are formed in the electric arc process. Crystallographic analysis of Er2 C94 in a cocrystal formed with Ni(OEP) reveals that the molecule is the carbide Er2 C2 @D3 (85)-C92 . Crystals of Er2 C2 @D3 (85)-C92 ⋅Ni(octaethylporphyrin)⋅2 C7 H8 are isostructural with those of Sm2 @D3 (85)-C92 ⋅Ni(octaethylporphyrin)⋅2 (chlorobenzene). Comparisons are made between the four crystallographically characterized endohedrals (Er2 C2 @D3 (85)-C92 , Gd2 C2 @D3 (85)-C92 , La2 C2 @D3 (85)-C92 , and Sm2 @D3 (85)-C92 ) that utilize the chiral D3 (85)-C92 cage.