Hydroperoxo reaction with

Scheme 2 Representation of equilibria between Ti04 framework species and H2O2/H2O solutions a formation of hydroperoxo species upon hydrolysis of a Ti - O - Si bridge b formation of hydroperoxo species toward reaction with a pre-existing defective Ti - OH species (see Sect. 3.8). Adapted from [49] with permission. Copyright (2004) by ACS...

SCHEME 4.3 Cytochrome P450 and peroxidase pathways to hydroperoxo-ferric intermediate or Compound 0 (5). Ferric cytochrome P450 (1) is reduced to the ferrous state (2), which can hind dioxygen to form oxy-ferrous complex (3). Reduction of this complex results in the formation of peroxo-ferric complex (4), which is protonated to give hydroperoxo-ferric complex (5). The same hydroperoxo-ferric complex is formed in peroxidases and catalases via reaction with hydrogen peroxide. 

Combined competition studies and stopped-flow measurements provided kinetic information on each of the two forms, L1(H20)Cr00H2+ and L Cr VOlOH2 1, in their reactions with PPh3. The hydroperoxo complex reacts by H + -catalyzed oxygen atom transfer, k 850M 2s while L1Crv(0)0H2+ reacts by electron transfer with k = AA x 105M-1 s 1. 

Haruta and Oyama proposed a slightly different mechanism [36t, 37s], in which the true intermediate was suggested to be the Ti-hydroperoxo species the latter is formed by adsorption of O2 onto Au, with the development of a Au -02 species, which then reacts with H2 to generate HP. HP finally generates the Ti-OOH active species over tetrahedral Ti sites, for the reaction with propene. Scheme 6.8 summarizes the main steps of the mechanism proposed [36tj. 

In many ways, the behavior of Re(Vll) is similar to that of the other metals, but in reactions with hydrogen peroxide, it prefers to form peroxo complexes, as does in certain cases, Mo(Vl). Ti(rV) forms exclusively hydroperoxo intermediates. 

Figure 17 Trinuclear complex [Cu 3(MES)] (a) is hydroxylated in a reaction with dioxygen, leading to a new ligand tricopper(I) complex [Cu 3(MES-0 )] + (b). This reacts with O2 giving peroxo(c) and hydroperoxo...

Thus a non-diffusible species such as Cu -hydroperoxo species can be generated as in Eq. (26) in Fig. 16 by Cu complexes in the presence of O2 and an electron (by first fixation of O2 on the metal center then reduction or by reaction with a beforehand-formed superoxide anion). This intermediate... 

Oxygen,—[Os(H)(NO)a(PPh3)a]+ reacts with oxygen to form [Os(OH)-(NO)2(PPh3)2]+, apparently by an insertion reaction, with the consequent hydroperoxo-intermediate [Os(OOH)(NO)a(PPhs)2]+, for which there is a precedent in the chemistry of the [Co(H)(CN)5] - anion. A preliminary communication concerning the insertion of oxygen into the cobalt-carbon bond of cobaloximes (29) to produce (30), wherein R = H, Me, or OH and... 

The kinetics and the mechanism of superoxide reduction by SORs have been studied by several researchers. It was suggested that SORs react with superoxide via an inner-sphere mechanism, binding superoxide at ferrous center to form a ferric hydroperoxo intermediate [46,48 50]. The rate constant for this reaction is equal to 108 109 1 mol-1 s-1 [46,49], This... 

The rate of the Ir(III) catalyzed reaction was found to be first-order in [Ir] and [H2DTBC], but independent of 02 concentration in chloroform (56). The mechanism proposed for the reaction (Scheme 4) postulates that the protonation of the hydroperoxo a-oxygen by the hydroxy group of the bonded catechol in Int 1 leads to the formation of H202. The o-qui-none ligand of Int 2 is replaced by the partially coordinated catechol in the next step. In order to comply with the experimental rate law, the rate-determining step needs to be the reaction of the oxygen adduct (B) with catechol. 

---