Molecular structure and stereoselective isomerization of (-)CD504-mer-bis(ethylenediamine-N-acetato)cobalt(III) bromide

Abstract The crystal structure of the (-) CD 504 - mer -[Co(edma) 2 ]Br isomer (edma=ethylenediamine- N -acetate) has been determined by a single crystal X-ray diffraction technique. The crystal was orthorhombic with space group P 2 1 2 1 2 1 , a =8.507(1), b =18.363(2), c =8.499(1) A, V =1327.6(3) A 3 , and Z =4. The cobalt atom is surrounded octahedrally by cis two oxygen and four nitrogen atoms of the two edma ligands, which coordinate to the cobalt ion in the meridional form. The (-) CD 504 isomer has an S ( C 2 ) configuration and both of the asymmetric nitrogen donor atoms in the two edma ligands take an S configuration. The (+) CD 504 - mer -[Co(edma) 2 ] + isomer isomerized to the (+) CD 543 - C 2 - trans (O) and C 1 - trans (O) isomers in a basic aqueous solution (pH 10.35) at 40 °C, and the formation ratio of these two isomers was c . 1:1. The isomerization mechanism of the (+) CD 504 - mer isomer was discussed in relation to its absolute configuration.