Some divalent transition metal complexes with α-dihydrazones

Abstract

An experimental and theoretical study was made of some divalent first-row transition metal complexes with two α-dihydrazone ligands, diacetyldihydrazone and glyoxaldihydrazone. The ligands and their complexes with iron(II), cobalt(II), nickel(II), and copper(II) were prepared, and other divalent ions were found not to react. The magnetic susceptibility, and infrared, electronic, and nuclear magnetic resonance spectra were determined; and iron(II) was found to form a very strong metal-ligand bond. A discussion of theoretical considerations of bonding was given, and General Hückel calculations on the ligand glyoxaldihydrazone and a hypothetical mono(glyoxaldihydrazone)iron complex performed. Considerable metal-ligand π-bonding was predicted. A comparison between theory and experiment confirmed the hypothesis of metal-ligand π-bonding for the iron(II) complexes; though not for the cobalt(II), nickel(II), and copper(II) complexes.