Hydroperoxo complexes structure

The similarity of olefin epoxidation by TM peroxo and hydroperoxo complexes with epoxidation by dioxirane derivatives R2CO2 and percar-boxylic acids RCO(OOH) was confirmed by computational studies [73-79]. This similarity holds in particular for the spiro-type transition structure. 

Crystal structure analysis has been carried out for several hydroperoxo complexes. The 0-0 bond length (1.40-1.48 A) (79,87,90,100,103,105) is significantly longer than that in superoxo complexes and close to the 1.49 A value for hydrogen peroxide (54). 

Figure 36 The structure of the Mo 1 peroxo/hydroperoxo complex [(02)2OMo(OOH)2MoO(02)2]2 1,6...

Zchnder and Fallab720 have demonstrated peroxo bridge formation via anation of cis-[Co(en)2(H20)2]3+ with H202. Reaction at pH 4.8 initially gives the hydroperoxo complex cis-[Co(OOH)(en)2(H20)]2+, which at higher pH reacts with [Co(OH)(en)2(H20)]2+ to yield racemic [(en)2Co(/i-0H,02)Co(en)2]3. Crystal structures of the dibridged species are available for the mesa and racemic722 forms. 

The reaction of 02 with the aqueous Cr2+ ion gives a number of Crra complexes including the hydroperoxo complex [(H20)5Cr(00H)]2+ it is reduced by Fe2+ to Cr3 via [(H20)sCr0]2+ as an intermediate.11 The structure of the nitrosyl complex [(H20)5CrN0]2+, previously formulated as a Cr1 compound, suggests that it is more properly described as a Cr111 complex of NO".12... 

Only a few examples of these unusual species have been reported. Recently, the synthesis and structural characterization of the hydroperoxo complex t(C5Me5)Ir(n-pz)3Rh(OOH)(dppe)](BF4), 249, were described (182). This complex was obtained by protonation of the heterodinuclear complex [(C,Mc5)(pz)Ir(/z-pz)2Rh(dppe)] (96) in the presence of dioxygen. An interest-... 

E.I. Solomon (2002). Electronic structure and reactivity of low-spin Fe(III)-hydroperoxo complexes Comparison to activated bleomycin. J. Am. Chem. Soc. 124, 10810-10822. 

Figure 14 Single-crystal X-ray structure of (69), a copper(II) hydroperoxo complex. All carbon-bound...

The structural difference imposed by the smaller metal chelate rings in the complex [Cu2(L55)] , five-membered instead of six-membered as in [Cu2(L66)], determine a completely different reactivity behavior with dihydrogen peroxide (107). The complex [Cu2(L55)] , undergoes a ligand hydroxylation reaction in the presence of H2O2, but this occurs at a benzylic position and with much slower rate (Scheme 8). The involvement of a hydroperoxo complex of [Cu2(L55)] has been suggested for this reaction, though no intermediate has been characterized yet. 

Unfortunately, there is no Ti-hydroperoxo compound of known structure to be used as a model. Conversely, the structure of several Ti-peroxo complexes are known by diffraction studies [111-113], all of them showing the side on r] geometry. None of these compounds is known to be active in partial oxidation reactions [114,115]. Similar considerations can be addressed... 

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