Planar Quinary Cluster inside a Fullerene Cage: Synthesis and Structural Characterizations of Sc₃NC@C₈₀-<i>I</i>_<i>h</i>

The endohedral fullerene Sc3NC@C80-Ih has been synthesized and characterized; it has an unprecedented planar quinary cluster in a fullerene cage. It is also the first chemical compound in which the presence of an unprecedented (NC)3− trianion has been disclosed. The fascinating intramolecular dynamics in Sc3NC@C80-Ih enables the whole molecule to display high polarity and promising ferroelectricity. This finding inspires the possibility that such a planar quinary cluster may be useful in constructing many other endohedral fullerenes.