SYNTHESIS, STRUCTURAL AND MICROSCOPIC ANALYSIS OF LOW VALENT COBALT CHELATES WITH N, O-DONOR LIGANDS

Abstract

The synthesis and characterization of low-valent cobalt chelates with N,O-donor ligands were investigated to explore their structural features and potential biomedical relevance. Cobalt(II) chloride was reacted with glycine and 8 hydroxyquinoline (oxine) under varying solvent conditions, followed by reduction attempts using sodium borohydride. The resulting complexes were analyzed through elemental analysis, FTIR spectroscopy, gravimetric halide determination, and single-crystal X-ray diffraction. The study revealed solvent-dependent coordination behavior: glycine yielded Co(gly)Cl₃ with selective amine coordination, oxine in aqueous media produced [Co(oxine)₂(H₂O)₂]Cl₂ with classical chelation, while oxine in THF/SOCl₂ formed [CoCl₄]⁻[C₉H₇NOH]⁺, where protonated oxine acted as a counter ion. Structural analysis confirmed distorted tetrahedral geometries and extensive hydrogen bonding interactions stabilizing the crystal lattice. Attempts to stabilize cobalt(I) complexes were inconclusive, highlighting the challenges of achieving square planar geometries in low-valent cobalt systems. These findings underscore the critical role of solvent environment and reaction conditions in dictating cobalt coordination chemistry and provide insights for future efforts to design cobalt-based complexes with potential anticancer properties analogous to platinum drugs.