Synthesis, characterization and catalytic application of some novel binuclear transition metal complexes of bis-(2-acetylthiophene) oxaloyldihydrazone for C[sbnd]N bond formation

Abstract

In the present work, synthesis, characterization and catalytic properties of some novel complexes derived from a Schiff base bis-(2-acetylthiophene) oxaloyldihydrazone with various transition metal ions and precursors have been reported. The complexes were characterized by IR, NMR, ESR, electronic and mass spectroscopy, magnetic moments and TGA studies. Molecular structures of the ligand and its Cu(I) complex are determined by single crystal X-ray diffraction. Electronic spectral studies exhibit a 6-coordinated geometry around metal centers for Co(II), Ni(II) and Cu(II) complexes, whereas 4-coordinated geometry for Cu(I) and Zn(II) complexes. ESR spectra indicate a distorted octahedral geometry for Cu(II) complex in DMSO frozen solution. The electro-chemical studies of Ni(II) and Cu(II) complexes reveal a metal based reversible redox behavior. The catalytic activity of the complexes has been demonstrated for the cross-coupling of arylboronic acids with various N-nucleophiles. Ni(II) complex exhibited the maximum impact on catalytic activity with the product yields ranging from 62% to 82%.