Electrochemical synthesis and structural characterisation of transition metal complexes with 2,6-bis(1-salicyloylhydrazonoethyl)pyridine, H4daps

Abstract

Neutral manganese, cobalt and nickel complexes of the pentadentate hydrazone 2,6-bis(1-salicyloylhydrazonoethyl)pyridine (H₄daps) have been prepared by means of electrochemical syntheses. They have been characterised by elemental analyses, IR spectroscopy, fast atom bombardment mass spectrometry (FAB) and magnetic susceptibility measurements. The molecular structures of [Mn(H₂daps)(py)₂] 1, [Co(H₂daps)(py)₂] 2, [Ni₂(H₂daps)₂]·CH₂Cl₂3, and [Ni₂(H₂daps)₂(py)₂]·CH₂Cl₂4 have been determined by X-ray diffraction. Depending on the nature of the metal ion, the dianionic [H₂daps]^2– ligand shows different co-ordination modes in these complexes: 1 and 2 are mononuclear with the metal atom in a pentagonal bipyramidal environment, 3 and 4 are binuclear with a helicate structure in which the nickel atoms attain octahedral co-ordination.