Synthesis and spectroscopic properties of cobalt(III) complexes of some aroyl hydrazones: X-ray crystal structures of one cobalt(III) complex and two aroyl hydrazone ligands

Abstract

Cobalt(III) complexes of diacetyl monooxime benzoyl hydrazone ( dmoBH 2 ) and diacetyl monooxime isonicotinoyl hydrazone ( dmoInH 2 ) have been synthesized and characterized by elemental analyses and spectroscopic methods. The X-ray crystal structures of the two hydrazone ligands, as well as that of the cobalt(III) complex [Co III(dmoInH) 2]Cl · 2H 2O , are also reported. It is found that in the cobalt(III) complexes the Co(III) ion is hexa-coordinated, the hydrazone ligands behaving as mono-anionic tridentate O,N,N donors. In the [Co III(dmoInH) 2]Cl · 2H 2O complex, the amide and the oxime hydrogens are deprotonated for both the ligands, while the isonicotine nitrogens are protonated. In the [Co III(dmoBH) 2]Cl complex, only the amide nitrogens are deprotonated. It is shown that the additional hydrogen bonding capability of the isonicotine nitrogen results in different conformation and supramolecular structure for dmoInH 2 , compared to dmoBH 2 , in the solid state. Comparing the structure of the [Co III(dmoInH) 2]Cl · 2H 2O with that of the Zn(II) complex of the same ligand, reported earlier, it is seen that the metal ion has a profound influence on the supramolecular structure, due to change in geometrical dispositions of the chelate rings.