Diphenylberyllium Reinvestigated: Structure, Properties, and Reactivity of BePh2, [(12-crown-4)BePh]+, and [BePh3]-

The first synthesis of BePh2 was accomplished almost a century ago. However, its structure has remained unknown so far, while the corresponding aryls of the elements adjacent to beryllium in the periodic table are well investigated. Herein, we present an improved synthesis for diphenylberyllium and show by X-ray diffraction that it forms a trinuclear complex in the solid state. NMR spectroscopy revealed that this structure is also retained in solution but exhibits dynamic behavior. Its stability against heat and coordinating solvents is discussed and the possible obstacles to the synthesis of BePh2 from BeCl2 are examined. In the process of this study two ether adducts, BePh2.Et2O and Be2Ph4.Et2O, have been characterized as well as the previously unknown triphenylberyllate anion. From the latter several single-crystal structures were obtained under various conditions, in which [BePh3](-) is either isolated or acts as a ligand for Li+. Furthermore, the crown ether induced selfionization of BePh2 is described and the resulting [(12-crown-4)BePh](+) cation was isolated, which shows an unusual 4+1 coordination around the Be atom.