SYNTHESIS AND CHARACTERIZATION OF HEXADENTATE COBALT(III) COMPLEXES WITH NEW EDTA-TYPE LIGANDS .4. CIRCULAR-DICHROISM OF THE TRANS(O5O6) ISOMER OF A COBALT(III) COMPLEX OF 1,3-PROPANEDIAMINE-N,N,N'-TRIACETIC-N'-3-PROPIONIC ACID

One of two geometrical isomers of the hexadentate cobalt(III) complex with 3-propanediamine-N,N,N'-triacetate-N'-3-propionate ion (1,3-pd3ap ) has been prepared and resolved. The NMR, electronic absorption and c ircular dichroism (CD) spectra were used to characterize the complex. The H-1 and C-13 NMR spectra of this geometrical isomer indicate that its six-membered propionate chelate ring is bound axially to the cobal t(III) ion, trans(O5O6)-[Co(1,3-pd3ap)]-. The (-)546-trans(0506)-[Co(1 ,3-pd3ap)]- complex, with a positive CD peak at lowest energy in the f irst spin-allowed absorption band region is tentatively assigned the L AMBDA absolute configuration. Spectral data for this complex are discu ssed in relation to those of other [Co(edta-type)]- complexes which va ry the size of carboxylate arms in the same way but maintain a six-mem bered diamine ring.