Beryllium Phosphine Complexes: Synthesis, Properties, and Reactivity of (PMe3 )2 BeCl2 and (Ph2 PC3 H6 PPh2 )BeCl2.

The directed synthesis, spectroscopic properties, and reactivity of bis(trimethylphosphine) beryllium dichloride (1) and bis(diphenylphosphino)propane beryllium dichloride (2) are reported, including the crystal structure of (PMe3 )2 BeCl2 (1). These four-coordinate beryllium compounds can be alkylated with n-butyllithium (n BuLi) to give three-coordinate (Ph2 PC3 H6 PPh2 )Ben Bu2 (3) and (PMe3 )Ben Bu2 (4). PMe3 can be removed from (PMe3 )Ben Bu2 (4) in vacuo to yield [n Bu2 Be]2 (5). For the first time, the presence of [n Bu2 Be]2 as a dimer in solution, which has been postulated for decades, could be observed spectroscopically. This novel, ether-free pathway provides access to beryllium dialkyl compounds that have never been in contact with oxygen-atom-containing reagents or solvents. This "freeness from oxygen" is crucial for semiconductor applications where oxygen is often unwanted and must be avoided at all costs.