SYNTHESIS AND CHARACTERIZATION OF COLBALT(III) COMPLEXES WITH A STEREOSPECIFIC LIGAND DERIVED FROM<i>S</i>-PROLINE

Abstract

Abstract This paper concerns the preparation, separation, and characerization of cobalt(III) complexes in which 2S, 2′S-1,1′-(ethane-1,2-diyl)bis(pyrrolidine-2-carboxylate), (pren), acts as etradentate ligand and the other two positions in the coordination sphere are occupied by monodentate or bidentate groups. The complex [Co(pren)(H2 O)2]+ exists only as the cis-α isomer, while in the case of [Co(pren)en]+ complexes, substantial yields of both cis-α and cis-β isomers have been isolated through a series of chromatographic steps and fractional crystallizations. The geometrical and optical configurations are assigned on the basis of absorption, circular dichroism, and 13C NMR spectra. In addition, the IR spectra of the complexes are discussed.