Synthesis, Characterization, and Optical Resolution of Electrically Neutral Octahedral Cobalt(III) Complexes Containing the Tetradentate Ligand

Three geometrical isomers of [Co(edda)(aa)] where edda=N′,N-ethylenediaminediacetato, aa=glycinato (gly), β-alaninato (β-ala), have been synthesized and characterized. They have been completely resolved into the enantiomers, except unsym-cis-fac-[Co(edda)(β-ala)], by the bis(μ-d-tartrato)diantimonate(III) anion, [Sb2(d-tart)2]2−, form of QAE-Sephadex resin with water as the eluent, and their absolute configurations have been determined based upon the circular dichroism spectra. It has been revealed that the Δ enantiomer is favored more by [Sb2(d-tart)2]2− than the Λ enantiomer irrespective of the kind of the geometrical isomers. Consideration on the mechanism of the optical resolution has been presented.