Sc₂C₂@C₈₀ Rather than Sc₂@C₈₂: Templated Formation of Unexpected <i>C</i>_2<i>v</i>(5)-C₈₀ and Temperature-Dependent Dynamic Motion of Internal Sc₂C₂ Cluster

Unambiguous X-ray crystallographic results of the carbene adduct of Sc2C82 reveal a new carbide cluster metallofullerene with the unexpected C2v(5)-C80 cage, that is, Sc2C2@C2v(5)-C80. More interestingly, DFT calculations and NMR results disclose that the dynamic motion of the internal Sc2C2 cluster depends strongly on temperature. At 293 K, the cluster is fixed inside the cage with two nonequivalent Sc atoms on the mirror plane, thereby leading to Cs symmetry of the whole molecule. However, when the temperature increases to 413 K, the 13C and 45Sc NMR spectra show that the cluster rotates rapidly inside the C2v(5)-C80 cage, featuring two equivalent Sc atoms and weaker metal−cage interactions.