Acylperoxo copper

Turning to the complexes of copper(II), copper(IV) is not stable and heterolysis of the 0—0 bond of the peroxide to form the copper(IV) oxo complex does not occur. In addition, the Lewis acidity of the copper(II) ion is not high enough to enhance the electrophilicity of the coordinated alkyl- or acylperoxide to promote direct oxo-incorporating reactions. With these points in mind, the inert activity of alkyl- and acylperoxo copper(II) complexes, experimentally observed, is understandable, and it is quite unlikely that the mechanism of copper monooxygenase parallels that of cytochrome P-450. 

Hydroperoxo, alkylperoxo, and acylperoxo copper(II) complexes While there is no direct experimental indication of involvement of dinuclear hydroperoxo copper(II) intermediate in the catalysis of tyrosinase, a dinuclear hydroperoxo copper(II) complex and related alkyl and acylperoxo complexes have been prepared either by reaction of a dinuclear jii-hydroxo complex [Cu2 (XYL-0 )(0H)] with XOOH (X=H, R, RCO) or by treating a peroxo complex [Cu2(XYL-0 )(02)] with X [138-140]. The acylperoxo complex was isolated and its molecular structure was established by X-ray crystallography (see Fig. 10). 

In light of the accepted mechanism for cytochrome P-450 (97-100), a superoxo-Cu(II) intermediate is further reduced, leading to dioxygen activation. Accordingly, a monomeric peroxo or hydroperoxo copper(II) complex serves as a synthetic model for these intermediates of copper-containing monooxygenases. However, no well-characterized complexes of these types are available to date. Formation of a monomeric hydroperoxo or acylperoxo complex was reported to occur when a trans-/u-l,2-peroxo complex, [(Cu(TPA))2(02)]z+, was treated with H+ or RC(O)+, but no details of the structures and properties of the complexes were provided (101). A related complex, a monomeric acylperoxo cop-per(II) complex, was synthesized (102). Low-temperature reaction of a dimeric copper(II) hydroxide complex, [Cu(HB(3,5-iPr2pz)3)]2(OH)2, with 2 equivalents of m-CPBA (3-chloroperoxybenzoic acid) yielded a monomeric acylperoxo complex whose structure was characterized by... 

Copper Superoxo Complexes 16.4.3 Copper Hydroperoxo, Alkylperoxo, and Acylperoxo Complexes 5 OXYGENATION OF C—H BONDS RELATED TO COPPER... 

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