Cobalt complexes aminocarboxylates

Oxidation of cobalt(II) aminocarboxylates [CoHEDTA] and [CoEDDA] by IO4 is first order in metal complex but two pathways with first- and second-order dependencies on [IO4] concentration are detected, indicating intermediate mono- and bis-complex formation. Both complexes are redox active and second- and third-order rate constants are 0.16M s and 2.59M "s for [CoHEDTA] and 0.120 M s and 1.53 M s for [CoEDDA] at pH 5, 25°C, and 0.5 M ionic strength. The third-order rates are pH dependent. 

The activation of the normally inert methylene group of glycine by coordination to a transition ion has been recognized for many years. The substantial increase in the acidity of the methylene hydrogens has been directly confirmed by deuterium labelling experiments,451 and has also been shown to occur in other a-aminocarboxylate complexes of cobalt(III)451 456 and platinum(II).457... 

---