Beryllium Crown Ether Complexes Reinvestigated

The species present in solutions of [12]crown‐4, [15]crown‐5, and [18]crown‐6 complexes with BeCl2 were investigated by 1H, 13C, and 9Be NMR spectroscopy. These are [(BeCl)([12]crown‐4)]+ (1), [(BeCl2)([15]crown‐5)] (2), and [(BeCl2)2([18]crown‐6)] (3), however in solution the majority of the crown ethers is not bound to beryllium. In case of [12]crown‐4 and [18]crown‐6 huge amounts of precipitate are formed, which were identified to be [(BeCl)([12]crown‐4)]Cl (1a) and compound 3, while [15]crown‐5 is capable of dissolving more than one equivalent of BeCl2 in dichloromethane.