Oligonuclear nickel(II) complexes sustained by intermolecular hydrogen-bonding

Reaction of Ni(OAc)(2) with the symmetric 'end-off' compartmental proligand 2,6-[N, N'-bis(2-hydroxy-phenylmethyl)-N, N'-bis(2-pyridylmethyl)aminomethyl]-4-methylphenol (H3L) in the presence of NaPF6 has been found to generate a homotetranuclear nickel(II) complex [(Ni4HL)(L)(OAC)(2)(H2O)(2)(HOAC)(2)]PF6. The crystal structure of the complex reveals that the complex is donor asymmetric and that the extended supra-ligand periphery is maintained by a tight hydrogen-bond between two pendant phenol/phenoxy groups of adjacent ligands and by further tight hydrogen-bonds between coordinated acetic acid molecules and the remaining pendant phenols of the ligand, generating a double acid salt of the type [CH3COO...H...LH...L...H...OOCCH3](5-). Reaction of H3L with Ni(OAc)(2) and NaClO4 in methanol gave the complex [Ni-2(HL)(OAc)(2)(OH2)(2)][ClO4]. The structure was determined by X-ray diffraction and showed that the complex exists as a dimer promoted by intermolecular hydrogen-bonding. (C) 2004 Elsevier B.V. All rights reserved.