MANGANESE (III) COMPLEXES WITH ETHYLENEDIAMINETETRAACETIC ACID

Abstract

Manganese(III) ethylenediaminetetraacetic acid complex has been prepared by various methods. The solid having a composition of KMnY.2.5H₂O is obtained as deep red crystals when the manganese dioxide suspension reacts with free ethylenediaminetetraacetic acid (H₄Y). The manganese was shown to be trivalent from its redox equivalent in its reaction with acidified iodide solution, and its magnetic moment, which was 4.89 Bohr magnetons, corresponding to four unpaired electron spins. The complex ion has an absorption maximum at 500 mμ (log ε = 2.67) in a slightly acidic medium. The variation of the visible spectra with pH has been studied by the spectrophotometric method, the value being obtained between the red and the yellow species. Observations have been made on the type of bond between the metal and carboxylate groups by the infrared spectral method. From its ion-exchange and pH titration behavior a formula, K[Mn(OH₂)EDTA].1.5H₂O, was suggested.