Complexes of iron(II), iron(III) and zinc(II) with condensation derivatives of 2-acetylpyridine and oxalic or malonic dihydrazide. Crystal structure of tris[(1-(2-pyridyl)ethylidene)hydrazine]iron(II) perchlorate

Abstract

Complexes of zinc and iron with N′, N′2-bis[(1E)-1-(2-pyridyl)ethylidene]ethanedihydrazide (H2L1) and N′ ,N′2-bis[(1E)-1-(2-pyridyl)ethylidene]propanedihydrazide (H2L2) were prepared. ZnII complexes with both ligands have an octahedral geometry. In the complex of ZnII with H2L1, the ligand is coordinated as a tridentate species in the monoanionic form, building two five-membered rings around ZnII. Three remaining coordination sites are occupied by water molecules, and in the outer sphere there is a ClO 4− ion. In the other ZnII complex, the H2L2 ligand is coordinated in the enol form as a tetradenate species, forming a five-memebered, a six-membered and a seven-membered ring, the remaining coordination sites being occupied by water molecules, while in the outer sphere there are two ClO 4− ions. The FeIII complex with H2L2 is a high-spin octahedral complex. The ligand is coordinated in the enol form, in a tetradentate fashion via pyridine and hydrazone nitrogens. The remaining two coordination sites in the complex are occupied by water molecules and a Cl− ion, and in the outer sphere there are two Cl− anions. The octahedral FeIII complex obtained from the reaction of FeCl3·6H2O and H2L1 in absolute ethanol has the formula [Fe(HL1)Cl2(H2O)]·1.5H2O. However, during coordination of the H2L1 ligand to FeIII in water, oxidative degradation of the side chain (–CO–CO–) and reduction of FeIII to FeII occurs, affording octahedral tris(1-(2-pyridyl)ethylidenehydrazine] ironII perchlorate, as confirmed by X-ray structure analysis.