Isolation and Structural Characterization of Two Very Large, and Largely Empty, Endohedral Fullerenes: Tm@<i>C</i>_3<i>v</i>-C₉₄ and Ca@<i>C</i>_3<i>v</i>-C₉₄

The structures of two newly synthesized endohedral fullerenes, Tm@C3v-C94 and Ca@C3v-C94, have been determined by single crystal X-ray diffraction on samples cocrystallized with NiII(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 C3 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.