Recently discovered monometallic cyanide cluster fullerenes are a novel family of endohedral molecules, whose chemical reactivity has not yet been probed. High-temperature trifluoromethylation of the yttrium cyanide cluster fullerene YCN@C-82(6), followed by high-performance liquid chromatography separation and an X-ray diffraction study of the two crystallized fractions, resulted in the structural characterization of YCN@C-82(6)(CF3)(26/28). In both molecules, exohedrally attached CF3 groups delimit the spherical pi system into localized double bonds, benzenoid rings, larger aromatic assemblies, and a conjugated fragment with the only intact pentagon that is involved in coordination to the interior Y atom. We also present theoretical results on charge distributions in the compounds reported.