Journal of the American Chemical Society, Vol.133, No.8, 2382-2385, 2011
Sc2C2@C-80 Rather than Sc-2@C-82: Templated Formation of Unexpected C-2v(5)-C-80 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 C-2v(5)-C-80 cage, that is, Sc2C2@C-2v(5)-C-80. 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 C-s symmetry of the whole molecule. However, when the temperature increases to 413 K, the C-13 and Sc-45 NMR spectra show that the cluster rotates rapidly inside the C-2v(5)-C-80 cage, featuring two equivalent Sc atoms and weaker metal-cage interactions.