Oxen complex

If the active oxidizing agent is not formulated as a ferric oxene complex, the questions then remain as to what is its electronic ground state and how does hydrocarbon oxidation occur ... 

The ferric oxene complex (6) is, of course, just one resonance formulation of 5 (see scheme 2). Moreover, the addition of dioxygen and two electrons to P-450 is equivalent to using... 

Figure 6.2 The mechanism of cytochrome-c-peroxidase complex formation, (a) Native enzyme, (b) Activated complex with the acid-base catalytic function of distal histidine (His) and stabilization of negative charge by arginine (Arg) residue of the active site, (c) Hypothetic intermediate oxene complex, (d) Complex I after intramolecular electron regrouping of oxene complex with Fe4+ and free radical X fragment formation.

The results of Table 4-2 confirm that the Fe KROOH)2+ adducts are effective dehydrogenation agents for substrates such as cyclohexadienes, substituted hydrazines, catechols, and thiols. For PhNHNHPh and 3,5-(f-Bu)2-l,2-(OH)2C6H2 the reaction efficiencies are comparable for HOOH and i-ClPhC(O)OOH as the oxidant but somewhat reduced for f-BuOOH. This may indicate that the oxene complex (2, Scheme 4-2) is the dominant reactive form and that f-BuOOH is hindered from assuming this configuration. Thus, the end-on configuration (2) with its oxene character is favored for HOOH and w-ClPhC(O)OOH. 

Most of investigators postulate the pentavalent iron oxene complex, P450-Fe =0, as the direct oxidant of a substrate by analogy with the reactive intermediates of the catalytic cycle of peroxidase, which have the oxoferryl group, Fe =0, in their active center. However, the Mossbauer and Raman spec-... 

A depth of this reaction correlates with the electron donor ability of Red and the stability degree of M +(Ox ) complex. The complexation causes anodic shift of metal redox potentials, which reaches almost 100 mV for transition metal cations (Maletin et al. 1979, 1980, 1983). 

Other mixed donor ligands. The preparation of Cs[Co(edda)X2] (edda = ethylenediamine-iViV -diacetate. X = NO2 or N3 — ox) complexes has... 

POMs exhibit two dominant modes of reactivity in redox processes. There are well-documented variations for each mode. Mode 1, which is the most frequent one when 02 is used as the oxidant, involves initial substrate oxidation (Equation (26)) followed by reoxidation of the reduced POM (Equation (27)). The net reaction is Equation (28). Mode 2, which is most frequent with oxygen donor oxidants including peroxides, involves initial activation of the oxidant, OX, by the POM with formation of a POM-OX complex (Equation (29)). There are three general fates of these complexes. They can directly react with substrate to form product (Equation (30)), transform to another complex, [POM-OX] (Equation (31)) which then oxidizes the substrate (Equation (32)), or form freely diffusing oxidizing intermediates that are not bound to the POM catalyst... 

This section contains some refinements of preceding considerations as applied to a map f X —> E of schemes, see (3.4.4)(b). Except in (3.9.1), which does not involve R/, we need / to be concentrated (= quasi-compact and quasi-separated). The main result (3.9.4) asserts that under mild restrictions on / or on the Ox-complex F, the projection map... 

Proof In the category of bounded-below Ox-complexes D, we can choose fiasque resolutions D F functorially, as follows for each g G Z, let 0 > F —>. .. be the (fiasque) Godement resolution... 

By (3.9.6)(a), every complex in Dqc(X) is D-isomorphic to a quasi-coherent complex. Therefore—and since a D-map a is an isomorphism iff the vertex of a triangle based on a is exact—we need only show if C is a quasircoherent Ox-complex such that R/ ((7) is exact then C is exact. 

Imitating the proof of [I, p. 238, Thm. 2.2.2[, we can then reduce the problem to showing that RF (F ) is pseudo-coherent for any bounded Ox-complex E whose component in each degree is a finite direct sum of sheaves of the form and... 

As in 4.3, a scheme-map / X —> F is called quasi-proper if R/ takes pseudo-coherent Ox-complexes to pseudo-coherent Oy-complexes. For example, when Y is noetherian and / is of finite type and separated then / is quasi-proper iff it is proper, see (4.3.3.3). We will need the nontrivial fact that quasi-properness of maps is preserved under tor-independent base change [LN, Prop. 4.4]. 

I, p. 173, 2.2.8b)] every pseudo-coherent Ox-complex is D-isomorphic to a bounded above complex of finite-rank locally free Ox-modules. Show that an Ox-complex F is pseudo-coherent iff for every n G Z there is a triangle P —> F R— P[l] with P perfect and R G (Dqc)[Pg.201]

Fig. 22. The possible stabilizing action of pbenolate ions on a Fs +.Ox complex with the subsequent oxygen transfer and regeneration of the iron complex by molecular oxygen.

MX Separation Process. The Mitsubishi Gas—Chemical Company (MGCC) has commercialized a process for separating and producing high purity MX (104—113). In addition to producing MX, this process gready simplifies the separation of the remaining Cg aromatic isomers. This process is based on the formation of a complex between MX and HF—BF. MX is the most basic xylene and its complex with HF—BF is the most stable. The relative basicities of MX, OX, PX, and EB are 100, 2, 1, and 0.14, respectively. 

A schematic of the MGCC process is shown in Figure 9. The mixed Cg aromatic feed is sent to an extractor (unit A) where it is in contact with HF—BF and hexane. The MX—HF—BF complex is sent to the decomposer (unit B) or the isomerization section (unit D). In the decomposer, BF is stripped and taken overhead from a condensor—separator (unit C), whereas HF in hexane is recycled from the bottom of C. Recovered MX is sent to column E for further purification. The remaining Cg aromatic compounds and hexane are sent to raffinate column E where residual BE and HE are separated, as well as hexane for recycle. Higher boiling materials are rejected in column H, and EB and OX are recovered in columns I and J. The overhead from J is fed to unit K for PX separation. The raffinate or mother Hquor is then recycled for isomerization. 

Rhodium complexes with oxygen ligands, not nearly as numerous as those with amine and phosphine complexes, do, however, exist. A variety of compounds are known, iucluding [Rh(ox)3] [18307-26-1], [Rh(acac)3] [14284-92-5], the hexaaqua ion [Rh(OH2)3] [16920-31 -3], and Schiff base complexes. Soluble rhodium sulfate, Rh2(804 )3-a H2 0, exists iu a yellow form [15274-75-6], which probably coutaius [Rh(H20)3], and a red form [15274-78-9], which contains coordinated sulfate (125). The stmcture of the soluble nitrate [Rh(N03)3 2H20 [10139-58-9] is also complex (126). Another... 

Some ligands have more than one atom with an unshared pair of electrons and hence can form more than one bond with a central metal atom. Ligands of this type are referred to as chelating agents the complexes formed are referred to as chelates (from the Greek chela, crab s claw). Two of the most common chelating agents are the oxalate anion (abbreviated ox) and the ethylenediamine molecule (abbreviated en), whose Lewis structures are... 

Draw all the structural formulas for the octahedral complexes of Co3+ with only ox and/or NH3 as ligands. 

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