Di(indenyl)beryllium
Ross F. Koby, Nathan D. Schley, Timothy P. Hanusa
Abstract
Abstract The bonding in beryllocene, [BeCp 2 ], took decades to establish, owing to its unexpected mixed hapticity structure (i.e., [Be(η 5 ‐Cp)(η 1 ‐Cp)]). Beryllium complexes containing the indenyl ligand, which is a close relative of the cyclopentadienyl anion, but which is also known to exhibit its own bonding peculiarities (e.g., facile η 5 ⇄ η 3 shifts), have remained unknown. Standard metathetical approaches to their synthesis (e.g., with K[Ind′] + BeX 2 in an ether solvent) give rise to intractable oils from which nothing identifiable can be isolated. In contrast, mechanochemical preparation, involving the solvent‐free grinding of BeBr 2 and potassium indenides, leads to the production of discrete (indenyl)beryllium complexes, including [Be(C 9 H 7 ) 2 ] ( 1 ) and [Be{1,3‐(SiMe 3 ) 2 C 9 H 5 }Br] ( 2 ). The former displays η 5 /η 1 ‐coordinated ligands in the solid state, but DFT calculations indicate that an η 5 /η 5 ‐conformation is less than 5 kcal mol −1 higher in energy.