Zigzag Sc₂C₂ Carbide Cluster inside a [88]Fullerene Cage with One Heptagon, Sc₂C₂@C_s(hept)-C₈₈: A Kinetically Trapped Fullerene Formed by C₂ Insertion?

A non-isolated pentagon rule metallic carbide clusterfullerene containing a heptagonal ring, Sc₂C₂@C_s(hept)-C₈₈, was isolated from the raw soot obtained by electric arc vaporization of graphite rods packed with Sc₂O₃ and graphite powder under a helium atmosphere. The Sc₂C₂@C_s(hept)-C₈₈ was purified by multistage high-performance liquid chromatography (HPLC), cocrystallized with Ni-(octaethylporphyrin), and characterized by single-crystal X-ray diffraction. The diffraction data revealed a zigzag Sc₂C₂ unit inside an unprecedented C_s(hept)-C₈₈ carbon cage containing 13 pentagons, 32 hexagons, and 1 heptagon. Calculations suggest that the observed nonclassical fullerene could be a kinetically trapped species derived from the recently reported Sc₂C₂@C_2v(9)-C₈₆ via a direct C₂ insertion.