A diuranium carbide cluster stabilized inside a C₈₀ fullerene cage

Area of Science:

• Actinide Chemistry
• Nanotechnology
• Materials Science

Background:

• Unsupported non-bridged uranium-carbon double bonds are fundamental targets in actinide chemistry.
• Studying actinide-ligand multiple bonding requires stable synthetic models.

Purpose of the Study:

• To synthesize and characterize a stable diuranium carbide cluster.
• To investigate the nature of uranium-carbon multiple bonding within a nanocontainer.

Main Methods:

• Encapsulation of a diuranium carbide cluster within I_h(7)-C₈₀ fullerenes using the Krätschmer-Huffman arc discharge method.
• Co-crystallization with nickel(II) octaethylporphyrin (Ni^II-OEP) to form single crystals.
• X-ray diffraction analysis, spectroscopic studies, and quantum-chemical calculations.

Main Results:

• Successful synthesis and stabilization of a bent diuranium carbide cluster (UCU) inside a fullerene cage (UCU@I_h(7)-C₈₀).
• Observed short uranium-carbon distances (2.03 Å) indicating covalent U=C double bond character.
• Quantum-chemical analysis suggests a formal oxidation state of +5 for both uranium atoms.

Conclusions:

• The endohedral fullerene UCU@I_h(7)-C₈₀ provides a stable system for studying unsupported uranium-carbon double bonds.
• The results affirm the covalent nature of the U(f¹)=C double bonds and offer insights into actinide-ligand multiple bonding.