Influence of hydrogen bonding on 'soft' coordination geometries: further examples

The X-ray crystal structures of five new crown ether complexes of Na+ and Ag+ are reported, namely: [Ag(18-crown-6)(H2O)(NO3)] (4), [Ag(18-crown-6)(CF3SO3)] (5), [Na(18-crown-6)(H2O)(2)] (CF3SO3) . 18-crown-6 (6), [Na(18-crown-6)(MeOH)(2)](BPh4) (7), [Na-2(dibenzo-30-crown-10)(H2O)(MeOH)](BPh4)(2) . MeOH (8). Compounds 4 and 7 exhibit intramolecular OH...O-crown hydrogen bonds resulting in marked distortions of the complex in order to simultaneously maximise ion-dipole interactions with the metal centre and satisfy the hydrogen bonding requirements of the system. Compound 6 exhibits intermolecular hydrogen bonding interactions to the uncomplexed crown ether, while compound 5 does not contain any hydrogen bonding protons but forms a surprising intermolecular pseudo-agostic CH2...Ag interaction. (C) 2003 Elsevier Science Ltd. All rights reserved.