Synthesis and Characterization of Cobalt Chelates Using 8-Hydroxyquinoline (Oxine) as a Ligand.

Abstract

Square planar complexes of cobalt in any of its common oxidation states are rare and attempt to make them either yield tetrahedral or octahedral complexes. The aim of this study was to synthesize and characterize tetrahedral or octahedral complexes of cobalt using selected chelating ligands such as 8-hydroxyquinoline (oxine) expected to have the same action as cis-platin used as anticancer drug.
The reactions of CoCl2 with 8-hydroxyquinoline (oxine) were studied under different solvent conditions under inert conditions. Reaction of cobalt (II) chloride with Oxine in tetrahydrofuran (THF) solvent gave unexpected blue crystals of the tetrachloridocobaltate (II) complex [CoCl4]-[C9H7NOH]+ in which protonated oxine is the counter cation.
The molecular structure of the complex [CoCl4]-[C9H7NOH]+ was confirmed using single crystal X-ray crystallography. It forms monoclinic crystals in the C2/c space group with respective unit cell parameters being= 90.00, = 91.0900, = 90.00; a = 15.1890(3), b = 7.99120(10), c = 16.6770(3).
When the same reaction was carried out in water/ethanol mixture, a yellow non crystalline solid, [Co(oxine)2(H2O)2]Cl2 was obtained. These compounds were characterized by melting point determination, elemental analysis and FTIR spectroscopy