Bent (metal)2C2 clusters encapsulated in (Sc2C2)@C82(III) and (Y2C2)@C82(III) metallofullerenes

A systematic powder X-ray structure study for (Sc2C2)@C82(isomer III) and (Y2C2)@C82(III) is carried out by the MEM/Rietveld method by using high resolution synchrotron radiation powder data. In both fullerene materials, two carbon atoms are encapsulated in the cage and a M2C2 bent cluster is most likely formed in the cage. The obtained cage structure of Sc2C84(III) is C82–C3V(8), which is the same as those of (Y2C2)@C82(III) and Y2@C82(III). The charge density of C2 is located at the center of fullerene cage. Two scandium atoms show the rotational disorder, indicating the presence of a rapid hopping motion inside C82–C3V(8) cage. The inter-atomic distances between metal and carbon atoms on fullerene cage are 2.29 Å for (Sc2C2)@C82(III), which is 0.2 Å smaller than that of (Y2C2)@C82(III).