The Isomerism of the (Ethylenediamine-<i>N</i>,<i>N</i>′-dipropionato)(ethylenediamine)cobalt(III) Ion and Its Stereoselective Isomerization Reaction

Abstract

Abstract Three isomers (one α and two β) of [Co(eddp)(en)]+ were prepared and optically resolved. The stereochemistry was studied on the basis of absorption, CD, and 13C NMR spectral data. Two β isomers, β(e-1) and β(e-2), were conformational diastereomers arising from a difference of the chirality around one of the asymmetric N atoms in a coordinated eddp ligand. The β(e-1) β(e-2) change was an inversion reaction at the asymmetric sec-N atom in the in-plane β-alaninate ring of the coordinated eddp, and the rate was slow. The α β(e-1) or β(e-2) change (coordination-site exchange reaction) was stereoselective and could be explained by the Co–O bond rupture mechanism proposed for Co(III)–edda complexes.