Isolation and structural characterization of two very large, and largely empty, endohedral fullerenes: Tm@C(3v)-C(94) and Ca@C(3v)-C(94).

The structures of two newly synthesized endohedral fullerenes, Tm@C(3v)-C(94) and Ca@C(3v)-C(94), have been determined by single crystal X-ray diffraction on samples cocrystallized with Ni(II)(octaethylporphyrin). Both compounds exhibit the same cage geometry and conform to the isolated pentagon rule (IPR). The metal ions within these rather large cages are localized near one end and along the C(3) axis. While the calcium ion is situated over a C-C bond at a 6:6 ring junction, the thulium ion is positioned above a six-membered ring of the fullerene.