Addition of CF group to endohedral fullerene ScN@I-C.

We report the first successful synthesis of a CF derivative of the stable endohedral fullerene ScN@I-C. Reaction with CFClCOONa yields a single C-symmetric ScN@C(CF) adduct where the CF group is inserted into a [6,6]-bond and opens it to 2.3 Å between the bridgehead carbon atoms. As evidenced by absorption and fluorescence spectroscopy as well as cyclic voltammetry, both the HOMO and the LUMO level of ScN@C(CF) are slightly (ca. 0.1 eV) downshifted with respect to the parent ScN@I-C, so the HOMO-LUMO gap remains essentially unchanged. The DFT calculations suggest that the reaction mechanism is not the previously assumed [2 + 1]-cycloaddition of :CF carbene but rather nucleophilic addition of CFCl anion followed by elimination of Cl and closing of the CF bridge via intramolecular nucleophilic substitution. Selective formation of the [6,6]-ScN@C(CF) turns out to be kinetically controlled and promoted by a particular orientation of the endohedral ScN cluster with respect to the CFCl addition site. In its turn, the CF addend partly hampers the rotation of ScN the endohedral cluster compared to its quasi-free reorientations in the parent ScN@I-C.