Sc2C2@D3h(14246)-C74: A Missing Piece of the Clusterfullerene Puzzle.

Clusterfullerenes with variable carbon cages have been extensively studied in recent years. However, despite all these efforts, C74 cage-based clusterfullerene remains a missing piece of the puzzle. Herein, we show that single-crystal X-ray crystallographic analysis unambiguously assigns the previously reported dimetallofullerene Sc2@C76 to a novel carbide clusterfullerene, Sc2C2@D3h(14246)-C74, the first experimentally proven clusterfullerene with a C74 cage. In addition, Sc2C2@D3h(14246)-C74 was charaterized by mass spectrometry, ultraviolet-visible-near-infrared absorption spectroscopy, 45Sc nuclear magnetic resonance, and cyclic voltammetry. Comparative studies of the motion of the carbide cluster in Sc2C2@D3h(14246)-C74 and Sc2C2@C2n (n = 40-44) revealed that a combination of factors, involving both the shape and size of the cage, is crucial in dictating the cluster motion. Moreover, structural studies of D3h(14246)-C74 revealed that it can be easily converted to Cs(10528)-C72 and Td(19151)-C76 cages via C2 desertion/insertion and Stone-Wales transformation. This suggests that D3h(14246)-C74 might play an important role in the growth pathway of clusterfullerenes.