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

Reaction of Ni(OAc)2 with the symmetric `end-offʹ 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 [Ni2(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.