Intramolecular and intermolecular OHO hydrogen bond in some nickel(II) complexes with tridentate amino–oxime ligands

Abstract

The 3-[(2-pyridyl)methylamino]-butan-2-one oxime (H-LNH-py) tridentate ligand forms with Ni(II) the pseudo-octahedral complex [Ni(II)(H-LNH-py)(LNH-py)]ClO 4 where the coordination of two ligands to the metal atom leads to the formation of an equatorial chelating system containing an intramolecular hydrogen bond (OHO) involving the oxime oxygen atoms. In acidic medium the [Ni(II)(H-LNH-py) 2](ClO 4) 2, complex is formed, deriving of the precedent by addition of a proton to the OHO bridge. A third complex, [Ni(II)(H-LNH-py) 2(C 6H 2N 3O 7)](C 6H 2N 3O 7), was isolated, as picrate, containing a double intermolecular hydrogen bond with a picrate ion. X-ray analysis of these compounds allows defining in all three cases the geometry of the hydrogen bonding fragments.