First- and second-sphere coordination chemistry of alkali metal crown ether complexes

Crown ethers exhibit an extremely versatile range of interactions with alkali metal cations in the solid state that goes far beyond simplistic 'size fit' considerations. In this review the structural chemistry of first and second-sphere alkali metal cation complexes of the crown ethers is examined with an emphasis on the role played by hydrogen bonding interactions to counter anions and other co-ligands such as water. An examination of the vast diversity of alkali metal crown ether complexes and the strong propensity of the crown ethers to act as hydrogen bond accepters suggests that hydrogen bonding plays a crucial role in determining overall structure, (C) 2001 Elsevier Science B.V. All rights reserved.