Iron complexes oxidized reaction products

Cyclohexene oxidation in the presence of the molybdenum complex, [C5Hr)Mo(CO)3]2, gave two major products at low conversion VI and VII nearly 1 1 mole ratio, Table V. The ketone, VIII, was formed in very low yield in contrast to oxidations using the iron complex. This reaction is far more selective than the oxidation of cyclohexene in the presence of Mo02(acac)2 reported by Gould and Rado (24). When a cyclohexene solution of V was exposed to [CsHsMk COJs] at 70°C, VI and VII were formed in approximately equimolar amounts (Table VI). These data show that the molybdenum complex efficiently catalyzes the epoxidation of cyclohexene by V before the allylic hydroperoxide decomposes substantially. Reaction 16 represents the predominant course of cyclohexene oxidation in the presence of cyclopentadienyltricarbonyl molybdenum dimer. 

Iron carbonyl complexes containing 77 -alkyl-77 -allyl coordinated hydrocarbon ligands are obtained in several ways. Nucleophilic addition to cationic iron complexes containing 77 -pentadienyl ligands yields (pentenediyl)iron complexes. Oxidatively-induced reductive elimination of these complexes can be utilized as a means to generate 1,2,3-trisubstituted cyclopropanes.The reaction of cationic cycloheptadienyl complexes (Scheme 22) with appropriate nucleophiles also yields the alkyl-allyliron carbonyl complexes. Fe(CO)s also reacts with a- or /3-pincnc in refluxing dioxane (Scheme 22) to produce an alkyl-allyliron complex. Recently, 1,2- and 1,4-disubstituted [(pentadienyl)Fe(CO)3] cations were shown to react with carbon nucleophiles, such as sodium dimethylmalonate, to yield 77 77 -allyl complexes as products. 

Although it is still unclear whether the formation of oxidized and hydroxylated products, which is the main pathway of catalytic activities of cytochrome-R-450 reductase, is mediated by free radicals, mitochondrial enzymes are certainly able to produce oxygen radicals as the side products of their reactions. It has been proposed in earlier studies [14,15] that superoxide and hydroxyl radicals (the last in the presence of iron complexes) are formed as a result of the oxidation of reduced NADPH cytochrome-P-450 reductase ... 

More recently, an environmentally benign method using air as oxidant has been developed for the oxidative cyclization of arylamine-substituted tricarbonyl-iron-cyclohexadiene complexes to carbazoles (Scheme 19). Reaction of methyl 4-aminosalicylate 45 with the complex salt 6a affords the iron complex 46, which on oxidation in acidic medium by air provides the tricarbonyliron-complexed 4a,9a-dihydrocarbazole 47. Aromatization with concomitant demetalation by treatment of the crude product with p-chloranil leads to mukonidine 48 [88]. The spectral data of this compound are in agreement with those reported by Wu[22j. 

A recently described method for insertion of a carbon monoxide molecule into the monoepoxide of a conjugated diene gives /3-lactones in high yield. This is achieved by reaction of iron pentacarbonyl with the starting vinyloxirane to give the 7r-allyl iron complex (66), which on oxidation with cerium(IV) ammonium nitrate gives the /3-lactone. In some cases, y-Iactone products can also be obtained from this reaction (8lJCS(Pi)270). 

The oxidation of [Cr(SH)(H20)5]2+ by I2 or Fe3+ under aerobic conditions in acid solutions gives the disulfido-bridged complexes [(H20)5CrS2Cr(H20)5]4+ and [(H20)sCr(S2H)Fe-(H20)5]4+ respectively (Scheme 100).967,968 The latter complex can also be obtained by substitution of chromium(III) in the former complex by iron(II) under acid conditions. The product distribution in the iron(UI) oxidation of [Cr(SH)(H20)5]2+ is pH dependent and at 298 K, pH = 1 the heteronuclear dimer [(H20)5Cr(S2H)Fe(H20)5]4+ constitutes over 80% of the product mixture. The rate of this reaction shows a [H+] 1 dependence, an observation consistent with [CrS(H20)5]+ being the kinetically active species. 

Co-oxidation of indene and thiophenol in benzene solution is a free-radical chain reaction involving a three-step propagation cycle. Autocatalysis is associated with decomposition of the primary hydroperoxide product, but the system exhibits extreme sensitivity to catalysis by impurities, particularly iron. The powerful catalytic activity of N,N -di-sec-butyl-p-phenylenediamine is attributed on ESR evidence to the production of radicals, probably >NO-, and replacement of the three-step propagation by a faster four-step cycle involving R-, RCV, >NO, and RS- radicals. Added iron complexes produce various effects depending on their composition. Some cause a fast initial reaction followed by a strong retardation, then re-acceleration and final decay as reactants are consumed. Kinetic schemes that demonstrate this behavior but are not entirely satisfactory in detail are discussed. 

Increase in the ruthenium concentration increases the stoichiometric factor, n in Eq. (2), from about 6 up to about 20, and in these more concentrated solutions rates of ruthenium(III) reduction are no longer first order in ruthenium(III). Under these conditions reaction products depend on the hydroxide concentration and include hydroxy-aromatic ligands [cf. Eq. (3)], carbonate, and trace amounts of dioxygen. Ruthenium complexes of ligands in which one pyridine ring had been completely oxidized were also characterized (2). This accounts for the carbonate, and the minor dioxygen yields could originate from complexes oxidized to ruthenium(IV) (8). Unlike the iron(III) system, neither free 2,2 -bipyridine nor the N-oxide was detected. 

It is known that Py adsorbed on hematite reacts with the surface at elevated temperature. The appearance of new IR bands after treatment above 423K indicates the formation of a new surface complex. It is believed that the new bands stem from surface-bound 2,2 -bipyridyl or o( -pyridone (refs. 18,19). Concomittantly with Py oxidation iron oxide becomes reduced and is losing its transmission. Whatever is the reaction product Gef -Fe Og catalysts start to oxidize Py at higher temperature and bind much less newly formed surface complex than ot-Fe Oj (Figs. 3 and 4). 

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