Reactions involving Oxygen and Hydrogen Peroxide

The slower formation of the / -hydroxo- -peroxo complex ion is the predominant step at high pH s and leads to irreversibility in the exchange of the 

When imidazole ligands are present in the fifth co-ordinating position, the rates are markedly increased compared with those for the other amines and this may reflect some hydrogen-bonding between the co-ordinated oxygen and the acidic proton on the imidazole ring. 

Several papers have been published on the reactions of cobalt(ii)-Schiff base complexes. A correlation between electronic structure and the chemical parameters of oxygenation has been described, the predominant single factor which is controlled by the fifth (axial) ligand being the energy change in the process Co i- Com. The latter oxidation state is favoured if the level of 

Tamura, K. Goto, and M. Nagayama, Shikizai Kyokaishi, 1972,45,629 Chem. Abs., 

The lower valency states of many metal ions and their complexes are oxidized by molecular oxygen. The initial reaction may involve either electron transfer to form the superoxide radical anion (a) or co-ordination of the dioxygen to form a complex (b). In some cases, reaction (b) occurs reversibly, as has been discussed in previous volumes of this Report. 

The exact nature of GGox is still uncertain. In the reaction of Og with a cobalt(n) macrocyclic diene, however, the ligand is oxidized to a [14]-4,7-diene-N4-one with a ketone oxygen on the central carbon of the pentane-2,4-di-iminato moiety. 

Cobalt(n) complexes with linear quinquedentate Schiff-base ligands have been prepared and their reaction with Og studied. Both monomeric superoxo- and dimeric peroxo-complexes have been identified depending on the ligand type. In one instance the adduct is considered to be of the form LCo —Og Co fiL in which the super- 

Several studies have been made on oxygen activation by metal complexes. In acetonitrile the oxidation of tributylphosphine is catalysed by [Co(acac)2]. In the presence of radical inhibitors the exclusive product is BU3PO. The rate law is given by the expression 

The mechanism of addition of the superoxide radical anion to cobalt(n) macro-cyclic complexes, [CoN4] +, has been studied in aqueous media. In the pH range 7—8, reaction of [Coii(4,ll-diene-N4)] and [Co (l,3,8,10-tetraene-N4)] with Oa yielded transient intermediates which have been characterized spectroscopically. The rate constants (1.4 x 10 and 1.6 x 10 1 mol s respectively) rule out the participation of HOa at these pH s. The transients are neither Co nor Co and it is concluded that the Oa adds to the metal centre at a labile axial site. The transient complex [OaCo(4,ll-diene-N4)]+ is also formed by the reaction of the corresponding cobalt(i) species with O2. The fate of these intermediates is still uncertain although one possibility is a dimerization to the dinuclear / -complex. 

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Reactions Involving Oxygen and Hydrogen Peroxide species, from the corresponding pentammine ... 

Reactions involving Oxygen and Hydrogen Peroxide may be interpreted using the mechanism... 

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