Nickel(II) complexes of fully and partially condensed Schiff-base ligands derived from tris(3-aminopropyl)amine and acetylpyridine

In the presence of nickel(II), 2-acetylpyridine condenses with tris(3-aminopropyl)amine in absolute MeOH to give the fully condensed Schiff-base complex [Ni(tptpy3)](2+). Although the ligand is potentially heptadentate, the metal atom is effectively six-coordinate, interaction with the bridgehead nitrogen being rather weak. However, when aqueous MeOH is used, the condensation is limited to a single step, and a complex of the pentadentate mono-Schiff base adduct is formed, [Ni(tptpy)(H2O)](2+), which was characterised by X-ray diffraction of its PF6- salt.