Copper peroxo

Oxidation Catalysis by Copper Peroxo and Superoxo Complexes. Copper ions and compounds participate in or catalyze a variety of oxidation reactions that consume 02. This is one of the several key biochemical roles of copper and much of the recent work on the subject has been done in efforts to model the biological systems. In some (non-biological) cases, e.g., the Wacker process, copper(II) itself may be the actual oxidant, but usually it serves as a carrier of oxygen. 

However, whereas these dinuclear cobalt species are invariably octahedral, dinuclear copper-peroxo species are tetrahedral or distorted square pyramidal. 

It is assumed that the oxidation by dopamine p-hydroxyiasc, containing a mononuclear active copper site, occurs via an intermediate copper peroxo complex Cu-OOH which generates a hydroxyl radical [521] ... 

Several copper peroxo complexes containing trl5(pyrid-2-ylmethyl)amine or related tripodal ligands have been reported. In contrast to (63)-(66), these complexes are characterized by a R02 —> Cu charge transfer band at Amax = 332-380 nm ( max = 890—4,300 mol dm cm Table i) i35,205,207,22r the values of vq o = 831—881 cm shown by (69)—(73) (Scheme 7, Table 1) 135,205,207 j-g similar to those of the pyrazolylborate complexes, however. The single-crystal structure of (69) shows a... 

Indeed, the oxygenation of 4-carbomethoxy-phenoIate by [Cu2(L66)] and [Cu2(L55)] was previously reported to occur also in acetonitrile at -40° C, where the reactions were normally carried out by exposing the Cu(I)-phenolate adduct to dioxygen 136). Since acetonitrile freezes above the temperature range of stability of the copper-peroxo complex, it could not be established whether the peroxo species binds and reacts directly with the phenolate in these systems. Moreover, when the phenol hydroxylation is carried out at room temperature, the main product obtained is the dimeric compound resulting from a formal Michael addition of the phenolate on... 

There are at least three possible roles for copper and oxygen in this system 1) the CuCl serves as an HCl scavenger, to reduce the concentration of HCl formed by spontaneous decomposition of Pd(II) and thus promote oxidation 2) the possible intermediates involved in the oxidation of CuCl by oxygen, such as copper peroxo species, might function as Lewis acids, oxidants or nucleophiles to promote oxidation and 3) the reaction might proceed via a Pd-OOH intermediate. 

Copper complexes in pyridine solution have been shown to be effective catalysts for the oxidative dimerization of aromatic amines to azo compounds [169]. A thorough treatment of oxidative dimerization reactions is beyond the scope of this review. However, recent reports give evidence for copper peroxo complexes [154] in these systems and for the intermediacy of a species of the type,... 

As a part of their ongoing investigations into the reaction of dioxygen with copper(I) complexes to identify copper-superoxo/peroxo intermediate species, Schindler and co-workers51-53 have also provided examples of a number of mononuclear copper(II) complexes (Table 1) (as well as copper(I) Section 6.6.4.2.1). 

During the course of modeling copper dioxygen chemistry, Kitajima et al. reported the synthesis of a yu-peroxo dinuclear complex with a 3,5-dimethyl-substituted tris(pyrazolyl)borate ligand, which showed remarkable physicochemical similarities to oxy-Hc and oxy-Tyr. Using a 3,5-di-isopropyl-substituted terminal ligand, they provided the first structural proof of the existence of peroxo dicopper(II) core (108) (copper geometry distorted square pyrami-... 

Tolman and co-workers investigated the oxygenation behavior of a copper(I) complex (790) (trigonal pyramidal) and demonstrated the formation of end-on peroxo-dicopper(II) species.58... 

From this perspective they reported the structure (complex (791) Cu-Cu 10.061 A) of a m-xylyl-based TACN ligand.583 Structures of four mononuclear copper(I) complexes ((792)-(795)), supported by tridentate macrocycle, were also reported by this group. They investigated their oxygenation behavior and in each case clean formation of side-on peroxo-dicopper(II) species was demonstrated.416... 

Using 1,4,8,11-tetraazacyclotetradecane, the structure of complex (800) (distorted trigonal planar Cu-Cu 6.739 A) was determined. Reactivity with 02 was investigated to demonstrate the formation of trans-l,2-peroxo species.585 As part of their work with copper(I) complexes with 02, the structure of a dicopper(I) complex ((801) distorted tetrahedral 7.04 A), supported by macrocyclic ligand environment, was reported by Comba and co-workers. Tolman and co-workers structurally characterized a three-coordinate copper(I)-phenoxide complex (802) (planar T-shaped) that models the reduced form of GO.587 The copper(I) analogue [Cu(L)][CF3-SO3]-0.43MeOI I (803) of a copper(II) complex (534) was also reported to demonstrate the role of ligand framework conformability in CV /Cu1 redox potentials.434 Wilson and co-workers... 

Figure 5.20 Square-pyramidal copper(II) peroxo complex exhibiting reversible oxygena-tion/deoxygenation behavior. (Adapted from references 47 and 41a.)...

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