Synthesis, physico-chemical, and spectral studies of dimeric cobalt(II), nickel(II), copper(II), zinc(II), and cadmium(II) complexes with dibutanone acyldihydrazones

Dimeric metal complexes of two new ligands, dibutanone malonic acid dihydrazone (dbmdh), and dibutanone succinic acid dihydrazone (dbsdh) with monomer composition [M(dbmdh)Cl-2] and [M(dbsdh)(H2O)(2)]Cl-2, M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II), were synthesized and characterized by elemental analyses, weight loss study, molecular weight determination, magnetic susceptibility measurements, electronic, ESR, infrared, H-1, and C-13 NMR spectral studies. The metal complexes have octahedral geometry. Both ligands are neutral tetradentate, coordinating through two > C=N nitrogen atoms and two > C=O oxygen atoms to two metal ions in a dimer. The molecular weight determination indicates dimers for all the metal complexes. ESR spectral studies indicate a tetragonally distorted octahedral stereochemistry for both Cu(II) complexes. The Delta Ms = 2 transition observed in these complexes suggest that the Cu(II) complexes are dimeric. ESR data indicate d(x2-y2) as the ground state and the bonding parameters, alpha(2), alpha(2), and beta(2)(1) suggest appreciable covalency of the in-plane sigma-bonding. The dbsdh complexes contain coordinated water as evinced by their weight loss.