Endohedral Cluster Compounds: Inclusion of Helium within C and C through Collision Experiments

Is host‐guest chemistry possible with fullerenes? Yes, but not as easily as once thought in the euphoric first weeks of preparative fullerene chemistry. Although the occurrence of metal‐ion inclusion is still controversial, indisputable evidence for inclusion of 3 He and 4 He within C and C radical ions has now been obtained. A reaction was initiated by collision of C and C ions with H 2 , D 2 , Ar, SF 6 , and He gases, but only He could be included, which agrees with the results of the initial calculations.