PREPARATION, STRUCTURE, AND SPECTRAL CHARACTERIZATION OF BIS[D-BETA-(2-PYRIDYL)-ALPHA-ALANINATO]COBALT(III), CO(D-PYALA)2+

The complex [Co(D-Pyala )2]NO3-1/2H2O was prepared by reaction of Co(II) or Co(III) with D-H2NCH(CH2C5H4N)CO(2-, D-Pyala-, the tridentate analogue of histidine. It was established by an X-ray crystal study of the complex that of the three possible isomeric forms, the most stable was that in which the carboxylate groups of the two ligands are mutually trans. This structure contrasts with that of the predominant isomer of the histidinate complex Co(L-his)2+, in which the imidazole groups are mutually trans. Infrared, 1H NMR, visible, ORD, and CD spectra of Co(D-Pyala)2+ are discussed and are entirely consistent with the solid-state structure. © 1979, American Chemical Society. All rights reserved.