Trapping a C₂ Radical in Endohedral Metallofullerenes:  Synthesis and Structures of (Y₂C₂)@C₈₂ (Isomers I, II, and III)

Abstract

Three isomers of yttrium carbide (Y 2 C 2 ) endohedral metallofullerenes, i.e., (Y 2 C 2 )@C 82 (I, II, III), have been synthesized and chromatographically isolated for the first time. The structures of (Y 2 C 2 )@C 82 (I, II, III) metallofullerenes have been characterized by 13 C NMR measurements, whose molecular symmetries have been determined to be C s, C 2 v, and C 3 v, respectively. In addition, a pure diyttrium metallofullerene, Y 2 @C 82 (III), has also been synthesized and structurally characterized. The 13 C NMR structural analyses indicate that (Y 2 C 2 )@C 82 (III) has exactly the same fullerene cage as that of Y 2 @C 82 (III). On the basis of the results, we propose a C 2 -trapping and loss of growth mechanism of dimetallofullerenes of (M 2 C 2 )@C 82 and M 2 @C 82 from M 2 @C 84, respectively.