ELECTROCHEMISTRY OF IMINODIACETATE COMPLEXES OF COBALT AT STATIONARY ELECTRODES

The redox behavior of cis-and trans-(iminodiacetato)cobaltate(III) has been studied in aqueous solution at stationary electrodes. The cis complex exhibits quasi-reversible behavior and a reduction potential estimated to be +0.36 V vs. the SHE. The trans isomer, however, exhibits more complex behavior, and upon reoxidation the cis isomer of the Co(III) system forms quantitatively. The results can be interpreted in terms of a model in which the cis isomer of the Co(II) system is the more stable and forms to the virtual exclusion of the corresponding trans species, whereas the trans species is preferred in the case of Co(III). The model also neatly rationalizes the synthetic methods which have been used to prepare the cis and trans isomers of the Co(III) complex. In addition, according to this model, an upper limit of 0.17 V vs. the SHE can be assigned to the reduction potential of the trans system. Finally, complications which occur in studying the complex at a mercury electrode are discussed, and condtions are described under which these effects are minimized. © 1979, American Chemical Society. All rights reserved.