POLAROGRAPHIC-DETERMINATION OF FORMATION-CONSTANTS FOR THE OXYGENATION OF SEVERAL COBALT(II) SCHIFF-BASE COMPLEXES

This paper descirbes a polarographic method for the determination of the formation constant for the binding of molecular oxygen with several cobalt(II) Schiff-base complexes. The method consists of determining, from the polarographic diffusion current for the reduction of the oxygenated complex, the oxygen partial pressure at which half of the complex is oxygenated. At this point, the partial pressure determined with a Clark-type membrane electrode is equal to the reciprocal of the formation constant, Koxy, for the oxygenated species. Koxy values of 0.128, 0.162 and 0.178 Torr-1 were obtained for the Co(II) SALEN, SALOPH and 3-methoxySALEN complexes, respectively, at 0° C in pyridine. This method can be used to determine Koxy values as large as 2.0 Torr-1 with an estimated uncertainty of 5-10%, based on the uncertainty of the oxygen electrode measurement. © 1979 Elsevier Sequoia S.A.