A nucleophilic beryllyl complex via metathesis at [Be–Be]2+

Owing to its high toxicity, the chemistry of element number four, beryllium, is poorly understood. However, as the lightest elements provide the basis for fundamental models of chemical bonding, there is a need for greater insight into the properties of beryllium. In this context, the chemistry of the homo-elemental Be–Be bond is of fundamental interest. Here the ligand metathesis chemistry of diberyllocene (1; CpBeBeCp)—a stable complex with a Be–Be bond—has been investigated. These studies yield two complexes with Be–Be bonds: Cp*BeBeCp (2) and [K{(HCDippN)2BO}2]BeBeCp (3; Dipp = 2,6-diisopropylphenyl). Quantum chemical calculations indicate that the Be–Be bond in 3 is polarized to such an extent that the complex could be formulated as a mixed-oxidation state Be0/BeII complex. Correspondingly, it is demonstrated that 3 can transfer the ‘beryllyl’ anion, [BeCp]−, to an organic substrate, by analogy with the reactivity of sp2–sp3 diboranes. Indeed, this work reveals striking similarities between the homo-elemental bonding linkages of beryllium and boron, despite the respective metallic and non-metallic natures of these elements. The chemistry of beryllium, one of the periodic table’s lightest elements, remains poorly understood. Now, a nucleophilic beryllium complex with a highly polarized Be–Be bond has been prepared—this compound could be seen as a mixed-oxidation state Be(0)/Be(II) complex. The Be–Be bond is cleaved upon reaction with an organic substrate.