Some new Schiff base ligands giving a NNOS coordination sphere and their nickel(II) complexes: Synthesis, characterization and complex formation

Some new tetradentate ligands with a NNOS coordination sphere were prepared and their corresponding nickel(II) complexes were synthesized and characterized by elemental analysis, IR, 1H NMR, UV–Vis and mass spectrophotometry. The thermodynamic formation constants of the complexes were measured spectrophotometrically, at a constant ionic strength of 0.1 M (NaClO4) at 25 °C in DMF solvent. The trend of the complex formation for nickel is as follows:[Ni(cdMesalen)] > [Ni(cdsalen)] > [Ni(cdPhsalen)][Ni(cdMesalMeen)] > [Ni(cdsalMeen)] > [Ni(cdPhsalMeen)[Ni(cd5OMesalen)] > [Ni(cd3OMesalen)] > [Ni(cd4OMesalen)][Ni(cd5OMesalen)] > [Ni(cdsalen)] > [Ni(cd5Brsalen)] > [Ni(cd5Clsalen)] > [Ni(cd5SO3Nsalen)] > [Ni(cd5SO3Nasalen)][Ni(cd5OMesalMeen)] > [Ni(cdsalMeen)] > [Ni(cd5BrsalMeen)] > [Ni(cd5ClsalMeen)] > [Ni(cd5SO3NasalMeen)] > [Ni(cd5NO2salMeen)]and[Ni(cdXsalMeen)] > [Ni(cdXsalen)].The structure of {methyl-2-[N-[2-(5-chloro-2-phenolate)methylidynenitrilo]ethyl}aminato(-1)-1-cyclopentenedithiocarboxylate nickel(II), [Ni(cd5Clsalen)], has been determined by X-ray crystallography. The coordination around nickel is essentially square-planar with a small tetrahedral distortion.

Graphical abstractSome new tetradentate ligands with a N2OS coordination sphere were prepared and their corresponding nickel(II) and copper(II) complexes were synthesized. The thermodynamic formation constants of the complexes were measured spectrophotometrically at 25 °C in DMF solvent. The structure of {methyl-2-[N-[2-(5-chloro-2-phenolate)methylidynenitrilo]ethyl}aminato(-1)-1-cyclopentenedithiocarboxyla-te nickel(II), [Ni(cd5Clsalen)], has been determined by X-ray crystallography. The coordination around nickel is essentially square-planar, with a small tetrahedral distortion.Figure optionsDownload full-size imageDownload as PowerPoint slide