Elusive uranium ‘sandwich’ cation isolated after more than 50 years, revealing how electron sharing holds its shape

Researchers have isolated uranocenium, the oxidised form of the landmark uranium sandwich compound uranocene, resolving a question that has remained open since uranocene was first made in 1968. The team showed that earlier attempts failed because the cation reacts with a commonly used electrolyte, not because it is inherently unstable. Under the right conditions, uranocenium is stable and electrochemically interconverts with uranocene as ferrocene, the benchmark redox pair in chemistry.