Uranium forms rare triple bond with carbon in newly isolated compound
In a study published in Nature Chemistry, an international team of researchers from Germany and the U.K., including chemists from The University of Manchester, has synthesized and characterized what they describe as the first isolable uranium Fischer-type carbyne, a compound in which carbon forms an unusual triple-bond interaction with uranium.
Researchers from Germany and the U.K. have synthesized and characterized the first ever isolable uranium Fischer-type carbyne, a compound where carbon forms an unusual triple-bond interaction with uranium. This discovery, published in Nature Chemistry, provides a new reference point for understanding the chemistry of actinides compared to more familiar transition metals.
Metal-carbon triple bonds are common in transition-metal chemistry, but creating a stable uranium compound with a similarly strong bond has proven difficult. Previous examples of uranium-carbon interactions were only observed under extreme conditions, such as extremely low temperatures or inside carbon cages known as fullerenes.
The team used a novel synthetic strategy involving a uranium precursor and a newly developed carbon-atom transfer reagent. This allowed them to create the compound and study it in detail using single-crystal X-ray diffraction, spectroscopy, magnetometry and advanced computational analysis. They confirmed that the compound exhibits the key features of a Fischer-type carbyne.
The uranium and carbon atoms in this compound are separated by 2.379(15) Å, which is longer than the typical distance for multiple bonding, but the scientists used quantum crystallography to visualize and confirm the uranium-carbon triple bond. This bond is formed through two-way electron sharing, with carbon donating two electrons to uranium, while uranium donates electrons back to carbon through two orthogonal one-electron bonds – a rare arrangement.
The new compound is relatively unreactive, as expected for a Fischer carbyne. However, chemical reduction was found to alter its bonding, providing further evidence for the arrangement of electrons in the molecule. The research is primarily important for fundamental chemistry, as it helps researchers understand how uranium forms bonds with carbon and places actinide chemistry within a broader context of how elements behave across the periodic table.
The study also highlights the potential of carbon-atom transfer reagents to create otherwise inaccessible compounds, which could enable future studies of uranium-carbon bonding and related actinide systems.
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