For the first time, researchers have created a solid compound containing a beryllium-beryllium bond (Science 2023, DOI: 10.1126/science.adh4419). The compound is diberyllocene, in which each beryllium atom is bound to a cyclopentadienyl unit (CpBeBeCp).
There had been decades of debate about whether Be–Be bonds could even exist, until Be2 was identified in the gas phase in 2009. Diberyllocene now provides “the first bottleable example,” says Josef T. Boronski of the University of Oxford, who created stable crystals of the new compound after reducing beryllocene (BeCp2) with a magnesium complex.
Beryllium usually prefers to exist in the +2 oxidation state, but quantum chemical calculations, X-ray crystallography, and spectroscopy studies all suggest that it adopts a highly unusual +1 oxidation state in diberyllocene. This enables the new compound to act as a reducing agent, opening up new avenues for beryllium chemistry. Boronski and his colleagues found that it reacts with a zinc complex to form an unprecedented zinc-beryllium bond, for example.
The team is now using diberyllocene to make other compounds in which electron-poor beryllium bonds to electron-rich partner metals, a potentially fruitful way to engineer catalytic activity. “That combination of electron rich and electron poor metals, you can envisage doing some quite interesting chemistry with small molecules like nitrogen and carbon monoxide,” says Oxford’s Simon Aldridge, who led the research team.