Putting a Terbium-Monometallic Cyanide Cluster into the C₈₂ Fullerene Cage: TbCN@<i>C</i>₂(5)‑C₈₂

The first terbium (Tb)-monometallic cyanide clusterfullerene (CYCF), TbCN@C82, has been successfully synthesized and isolated, whose molecular structure was determined unambiguously as TbCN@C2(5)-C82 by single crystal X-ray diffraction. The C2(5)-C82 isomeric cage represents a new cage capable of encapsulating a monometallic cyanide cluster. The C–N bond length within the encaged TbCN cluster is determined to be 0.94(5) Å, which is smaller by at least 0.17 Å than those of the reported C–N triplet bonds in traditional cyanide/nitrile compounds and cyano coordination complexes. An electronic configuration of [Tb3+(CN)−]2+@[C82]2– was proposed for TbCN@C82.