The Stereochemistry of the Six Geometrical Isomers of the Bis(ethylenediamine-N-acetato)cobalt(III) Ion, [Co(edma)2

Abstract

Abstract All of the six geometrical isomers possible in [Co(edma)2]+ (edma: ethylenediamine-N-acetate) were isolated, and the five chiral isomers were resolved into optically active isomers by a column-chromatographic method. Their structures were determined on the basis of the X-ray analysis and the visible absorption, 1H NMR, and CD spectral data. One of the methylene protons in the glycinate-ring of the facially coordinating edma is stereospecifically exchanged by a deuteron in the basic D2O solution, and its deuteration rate is influenced by the ligating atoms in the trans position. A 1H NMR method to determine the absolute configurations of the optically active isomers, which contain the stereospecifically deuterated edma, is reported and applied to the [Co(edma)2]+ systems. The relationship between the absolute configurations and the CD spectral behaviors of these complexes is also discussed.