STEREOSELECTIVITY IN MIXED TRIS‐TYPE COMPLEXES OF COBALT(III) WITH L‐PROLINE AND L‐ OR D‐ASPARTIC ACID

Mixed complexes with L-proline and L- or D-aspartic acid, [Co(L-pro)3−n(L-(or D-)asp)n]n− (n=1,2), have been prepared and separated into a number of stereoisomers by means of ion-exchange chromatography. The structures of the isomers have been characterized by various spectral data. As to the [Co(L-pro)(D-asp)2]2− and [Co(L-pro)2(D-asp)]− complexes, all of three possible mer-isomers have been isolated in their Δ-forms. The formation ratios among the isomeric species in the reaction system have been estimated spectrophotometrically. Marked differences in stereoselectivity have been found between the L-aspartato complexes and the corresponding D-aspartato complexes. These selectivities have been qualitatively explained in terms of the interaction between the dangling β-carboxylate group in a chelated aspartate ion and the adjacent ligand.