There’s been an exciting breakthrough from the folks at Lawrence Berkeley National Laboratory—introducing ‘berkelocene,’ the first-ever organometallic compound featuring the radioactive element berkelium. This discovery is shaking up what we thought we knew about the heavy actinides, especially those elusive elements beyond uranium on the periodic table.
Interest in these actinide-carbon bonds isn’t new. It dates back to the Manhattan Project when scientists were exploring isotope separation. A recent study in Science highlights this new molecule, ‘berkelocene,’ named because it shares a structural kinship with ‘uranocene.’ Imagine a berkelium atom nestled between two carbon rings. This structure was confirmed using some pretty advanced X-ray diffraction techniques over at Berkeley Lab.
Stefan Minasian, a leading scientist there, shared, “This is the first time we’ve got evidence of a chemical bond forming between berkelium and carbon.” This study is providing fresh insights into how berkelium and its actinide relatives behave compared to other elements.
Creating berkelocene is no small feat, especially given the tricky nature of berkelium. Discovered back in 1949 by Glenn Seaborg at Berkeley Lab, berkelium is not only highly radioactive but also quite rare, produced in tiny amounts globally. Its organometallic compounds are sensitive to air and can be pyrophoric, which means they need careful handling.
Polly Arnold, a co-author and director at Berkeley Lab’s Chemical Sciences Division, explained, “Only a few places worldwide can safely handle both the compound and the worker, managing the hazards of a highly radioactive material that reacts vigorously with oxygen and moisture.” The team used custom gloveboxes for air-free syntheses with radioactive isotopes, working with just 0.3 milligrams of berkelium-249 for their experiments.
One particularly interesting outcome came from electronic structure calculations by Jochen Autschbach at the University of Buffalo. They found that berkelocene’s berkelium atom reaches a tetravalent oxidation state (+4), stabilized by its carbon bonds. This finding is a bit of a surprise, as it contradicts earlier models of the periodic table, which suggested berkelium behaved like the lanthanide terbium.
Minasian pointed out, “Traditional periodic table understanding suggests berkelium would act like lanthanide terbium.” Yet, Arnold added that the berkelium ion is more stable in the +4 oxidation state than anyone anticipated.
This discovery is prompting the development of more accurate models to understand actinide behavior, which is crucial for tackling nuclear waste storage issues. As Minasian concluded, “Studying higher symmetry structures helps us grasp the logic nature uses to organize matter at the atomic level.”
