Crystallographic Characterization of Er2C2@C80–88: Cluster Stretching with Cage Elongation

Six dierbium carbide endohedral metallofullerenes have been synthesized and chromatographically isolated. Single-crystal X-ray diffractometry unambiguously ascertains their structures as Er 2 C 2 @ C 2 v (5)-C 80, Er 2 C 2 @ C s (6)-C 82, Er 2 C 2 @ C s (15)-C 84, Er 2 C 2 @ C 2 v (9)-C 86, Er 2 C 2 @ C s (15)-C 86, and Er 2 C 2 @ C s (32)-C 88, respectively. The Er···Er distances of the major erbium sites inside the C s (6)-C 82, C 2 v (5)-C 80, C s (15)-C 84, C s (15)-C 86, C 2 v (9)-C 86, and C s (32)-C 88 cages are 3.801, 3.860, 4.062, 4.066, 4.307, and 4.372 Å, respectively, which show a linear tendency with an increase in the major axis of the fullerene cages (8.064, 8.238, 8.508, 8.582, 8.815, and 8.953 Å, respectively). Furthermore, the electrochemical and molecular orbital analyses reveal that the redox chemistry of the Er 2 C 2 @C 80–88 isomers is associated with the carbon cage, which is different from the situations found for typical dimetallofullerenes, such as Y 2 @C 82, Er 2 @C 82–84, and Lu 2 @C 82,86 isomers, which show metal-dependent oxidation processes, indicating the importance of C 2 insertion in carbide cluster metallofullerenes.