Self-driven carbon atom implantation into fullerene embedding metal-carbon cluster.

Hundreds of members have been synthesized and versatile applications have been promised for endofullerenes (EFs) in the past 30 y. However, the formation mechanism of EFs is still a long-standing puzzle to chemists, especially the mechanism of embedding clusters into charged carbon cages. Here, based on synthesis and structures of two representative vanadium-scandium-carbido/carbide EFs, VSc ₂ C@ I _h (7)-C ₈₀ and VSc ₂ C ₂ @ I _h (7)-C ₈₀ , a reasonable mechanism-C ₁ implantation (a carbon atom is implanted into carbon cage)-is proposed to interpret the evolution from VSc ₂ C carbido to VSc ₂ C ₂ carbide cluster. Supported by theoretical calculations together with crystallographic characterization, the single electron on vanadium (V) in VSc ₂ C@ I _h (7)-C ₈₀ is proved to facilitate the C ₁ implantation. While the V=C double bond is identified for VSc ₂ C@ I _h (7)-C ₈₀ , after C ₁ implantation the distance between V and C atoms in VSc ₂ C ₂ @ I _h (7)-C ₈₀ falls into the range of single bond lengths as previously shown in typical V-based organometallic complexes. This work exemplifies in situ self-driven implantation of an outer carbon atom into a charged carbon cage, which is different from previous heterogeneous implantation of nonmetal atoms (Group-V or -VIII atoms) driven by high-energy ion bombardment or high-pressure offline, and the proposed C ₁ implantation mechanism represents a heretofore unknown metal-carbon cluster encapsulation mechanism and can be the fundamental basis for EF family genesis.