The complicated oxidation kinetics of the reaction of reacts with O 2 by a substitution process to form [Fe II (cdta)O 2 ] 2-; (2) electron-transfer to form an Fe III -[Fe II (cdta)] [cdta = 1,2-(N,NЈ-cyclohexanediamine)tetraacetate] with molecular oxygen was investigated as a superoxo species;
(3) subsequent bridge formation followed by electron-transfer to give
, pH, temperature and pressure. In the presence of an excess of [Fe II (cdta)] three steps could be and (4) a fast decomposition of the peroxide intermediate yielding the monomeric [Fe III (cdta)] and H 2 O 2 . Rate and observed, for which the following rate constants were found at 25°C; k 1 = 1080 ± 16 M -1 s -1 , k 2 = 103 ± 4 M -1 s -1 and k 3 = activation parameters for these steps are reported and discussed in terms of the postulated mechanism and in 59 ± 5 M -1 s -1 . These reaction steps can be accounted for in terms of the following mechanism: (1) [Fe II (cdta)H 2 O] 2- reference to available literature data.
The present work describes how the selected chelate can Kinetic Measurements [a] Institute for Inorganic Chemistry, University of Erlangen-Kinetic traces measured in the presence of an excess of Nürnberg,
[Fe II (cdta)] showed a complicated multistep process. In con-Egerlandstraße 1, 91058 Erlangen, Germany trast to the [Fe II (edta)] system, we could now fit the kinetic