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 (H(2)L1) and N', N'(2)-bis[( 1E)-1-(2-pyridyl) ethylidene] propanedihydrazide (H(2)L2) were prepared. Zn-II complexes with both ligands have an octahedral geometry. In the complex of Zn-II with H(2)L1, the ligand is coordinated as a tridentate species in the monoanionic form, building two five-membered rings around Zn-II. Three remaining coordination sites are occupied by water molecules, and in the outer sphere there is a ClO4- ion. In the other Zn-II complex, the H(2)L2 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 ClO4- ions. The Fe-III complex with H(2)L2 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 Fe-III complex obtained from the reaction of FeCl(3)center dot 6H(2)O and H(2)L1 in absolute ethanol has the formula [Fe(HL1) Cl-2(H(2)0)] center dot 1.5H(2)O. However, during coordination of the H(2)L1 ligand to Fe-III in water, oxidative degradation of the side chain ( - CO - CO -) and reduction of Fe-III to Fe-II occurs, affording octahedral tris(1-(2-pyridyl) ethylidenehydrazine] iron(II) perchlorate, as confirmed by X-ray structure analysis.