Synthesis and electrochemical investigation of a series of iron(II) complexes with bidentate, tridentate and hexadentate ligands

Abstract

Iron(II) complexes of a bidentate, a hexadentate and a series of tridentate ligands have been prepared and characterized. Electrochemical properties have shown that of the tridentate ligands, those capable of dπ- pπ bonding between the pyridyl rings and central ligand atom can stabilize formal low oxidation states (I,O, −I) of the metal. A bidentate ligand, 2-(2-pyridyl) imidazole although resembling 2,2′-bipyridine in structure, does not stabilize any low oxidation states and its iron(II) complex is reduced irreversibly to iron(O). The iron(II) complex of a hexadentate ligand, tetra(2-picolyl)ethylenediamine, is reduced in two, one electron steps to yield formal Fe(I) and Fe(O) oxidation states. However, both of these reductions are totally irreversible at a Pt and HMDE electrode.