Dicopper peroxide complex

The latter binding mode has been observed for oxyhemocyanin (77) and in a dicopper(II) peroxide complex (78). Figure 2 illustrates structures for the peroxo intermediate which are most compatible with its spectroscopic parameters, as well as another, less likely, possibility (51). 

A side-on p,-Tq2 Tq2-peroxo dicopper(II) complex. A very important development in copper-dioxygen chemistry occurred in 1989 with the report by Kitajima et al. [10,108] that another Cu202 species could be prepared and structurally characterized by using copper complexes with a substituted anionic tris(pyrazolyl)borate ligand. This intensely purple compound, Cu[HB(3,5-iPr2pz)3] 2(02) (5), was prepared either by reaction of Cu[HB(3,5-iPr2pz)3] (4) with 02 or by careful addition of aqueous hydrogen peroxide to the p-dihydroxo... 

Early after the detection and characterization of discrete CU2O2 compounds such as the TMPA end-on peroxo and Nn side-on peroxo dicopper(II) compounds, we began to investigate their oxidative reactivity properties in order to see if we can mimic biological functionality and also to learn about the fundamental properties of each types of compounds. Analysis of the end-on peroxo dicopper(II) complexes, [ Cu(TMPA) 2 (p-1,2-02)] and [Cu 2(XYL-0 )(02)] (a terminal end-on (P-I-O2) compound formed from the low-temperature oxygenation of [Cu 2(XYL-0 )] see Fig. 23) 100 and their reaction with acids, organic peroxides, and substrates like 2,4-di- cr -butylphenol, and triphenylphosphane, gave a clear... 

The second phase of the reaction observed in the optical trace vs. time is the global catalytic cycle, which contains reactions 12 and 13 and the oxygenation of the dicopper(I) complex. The closure of the cycle can be achieved in different ways, which are outlined as path a, paths 6 + rf, and path c in Scheme 17. What discriminates between them is the reactivity of the CU2O2 species, since it can react with protons according to path a and 6, or oxidize the catechol according to path c. For the reactions catalyzed by the Cu(II) cmplexes of L55, L66, and EBA no detectable amount of dihydrogen peroxide was found in solution therefore, the only possible path is c. Thus, the catalytic cycle can be represented by the following reactions ... 

In case of the Cu(Tpzb) complex (5), formation of /u.- j j -peroxo dicopper(II) complex (1) from 11 was confirmed imder dioxygen (89) in both toluene and THF. For the Cu(L ) complex as well as the Cu(L = ) and Cu(L" ") complexes (6), it was reported that 11 afforded complex 1 in nonpolar solvents such as toluene (97). 1 reacts with phenols to regenerate 2 (98) and hydrogen peroxide (99). Hence, this catalytic system would allow only the regioselective coupling process from 2 and/or 3 and completely exclude free-radical coupling reactions the present reaction is thus recognized as radical-controlled oxidative polymerization. 

Figure 11 Absorption spectrum of TlHg Lc oxygen intermediate/peroxide-level intermediate (a) compared to spectra of peroxo-dicopper(II) model complexes (b)-(e). Structural types indicated (after Solomon and...

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