Iron compounds addition reactions

Condensation of vinyl chloride with formaldehyde and HCl (Prins reaction) yields 3,3-dichloro-l-propanol [83682-72-8] and 2,3-dichloro-l-propanol [616-23-9]. The 1,1-addition of chloroform [67-66-3] as well as the addition of other polyhalogen compounds to vinyl chloride are cataly2ed by transition-metal complexes (58). In the presence of iron pentacarbonyl [13463-40-6] both bromoform [75-25-2] CHBr, and iodoform [75-47-8] CHl, add to vinyl chloride (59,60). Other useful products of vinyl chloride addition reactions include 2,2-di luoro-4-chloro-l,3-dioxolane [162970-83-4] (61), 2-chloro-l-propanol [78-89-7] (62), 2-chloropropionaldehyde [683-50-1] (63), 4-nitrophenyl-p,p-dichloroethyl ketone [31689-13-1] (64), and p,p-dichloroethyl phenyl sulfone [3123-10-2] (65). 

In addition, several addition reactions have been reported for the iron complex [Fe(CNCH3)j] with hydrazine and with methylamine (99) the products (XVI) and (XVII), respectively, are described. A crystal structure study on the latter compound was carried out. 

The iron slurries show exceptional reactivity toward oxidative addition reactions with carbon halogen bonds. In fact, the reaction with C.FcI is so exothermic that the slurry has to be cooled to 0 °C before the addition of C F L The reaction of iron with C F Br is also quite exothermic, hence, even for this addition, the iron slurry is cooled to about 0 ° C. The organoiron compound formed in the above reactions, solvated Fe(C.F )2, reacts with CO at room temperature and ambient pressure to yiela Fe(C,F3)2(CO)2(DMEL. 

As you learned in Chapter 1, aromatic compounds do not react in the same way that compounds with double or triple bonds do. Benzene s stable ring does not usually accept the addition of other atoms. Instead, aromatic compounds undergo substitution reactions. A hydrogen atom or a functional group that is attached to the benzene ring may be replaced by a different functional group. Figure 2.6 shows two possible reactions for benzene. Notice that iron(III) bromide, FeBrs, is used as a catalyst in the substitution reaction. An addition reaction does not occur because the product of this reaction would be less stable than benzene. 

The type and quality of the pigment are determined not only by the nature and concentration of the additives, but also by the reaction rate. The rate depends on the grades of iron used, their particle size, the rates of addition of the iron and nitrobenzene (or another nitro compound), and the pH value. No bases are required to precipitate the iron compounds. Only ca. 3 % of the theoretical amount of acid is required to dissolve all of the iron. The aromatic nitro compound oxidizes the Fe2 + to Fe3 + ions, acid is liberated during hydrolysis and pigment formation, and more metallic iron is dissolved by the liberated acid to form iron(II) salts consequently, no additional acid is necessary. 

One of the simplest biochemical addition reactions is the hydration of carbon dioxide to form carbonic acid, which is released from the zinc-containing carbonic anhydrase (left, Fig. 13-1) as HC03-. Aconitase (center, Fig. 13-4) is shown here removing a water molecule from isocitrate, an intermediate compound in the citric acid cycle. The H20 that is removed will become bonded to an iron atom of the Fe4S4 cluster at the active site as indicated by the black H20. An enolate anion derived from acetyl-CoA adds to the carbonyl group of oxaloacetate to form citrate in the active site of citrate synthase (right, Fig. 13-9) to initiate the citric acid cycle. 

Nitroaromatic compounds (NACs) are one of the widespread contaminants in the environments. Sources of NACs are numerous they originate from insecticides, herbicides, explosives, pharmaceuticals, feedstock, and chemicals for dyes (Agrawal and Tratnyek, 1996). Under anaerobic conditions, the dominant action is nitro reduction by zero-valent iron to the amine. Other pathways do exist, such as the formation of azo and azoxy compounds, which is followed by the reduction of azo compounds to form amines. Also, in addition to the possibility of azo and azoxy compounds, phenylhydrox-ylamine may be an additional intermediate (Agrawal and Tratnyek, 1996). Nitrobenzene reduction forms the amine aniline. Known for its corrosion inhibition properties, aniline cannot be further reduced by iron. Additionally, it interferes with the mass transport of the contaminant to the surface of the iron. The overall reaction is as follows ... 

The bromine solution is red the product that has the bromine atoms attached to carbon is colorless. Thus a reaction has taken place when there is a loss of color from the bromine solution and a colorless solution remains. Since alkanes have only single C—C bonds present, no reaction with bromine is observed the red color of the reagent would persist when added. Aromatic compounds resist addition reactions because of their aromaticity the possession of a closed loop (sextet) of electrons. These compounds react with bromine in the presence of a catalyst such as iron filings or aluminum chloride. 

Li and coworkers published addition reactions of ethers, sulfides, or tertiary amines 40 to p-dicarbonyl compounds 39 (Fig. 8) [96]. Fe2(CO)9 proved to be the catalyst of choice and di-tert-butyl peroxide the optimal oxidant. a-Functionalized p-dicarbonyl compounds 41 were isolated in 52-98% yield. Although the details of the catalytic cycle remain unclear, it seems to be likely that the peroxide is reductively cleaved by the Fe(0) catalyst leading to an Fe(I) complex and a ferf-butoxyl radical, which abstracts the a-hydrogen atom of 40. Addition of the resulting radical to the free enol form of 39 or the corresponding iron enolate of 39 may subsequently occur. It remains unclear, however, whether the main catalytic reaction proceeds on an Fe(0)-Fe(I) oxidation stage or whether further oxidation of initially formed Fe(I) rather leads to an Fe(II) catalyst. This cannot be excluded,... 

The compound may react as a typical metal(0) species, susceptible to substitution and oxidative addition reactions. Both are promoted by the unsaturated nature of the molecule, which is the first stable four-coordinate iron(0) species to be observed at ambient temperature. 

The solid compound slowly decomposes at room temperature and quickly at 70°, while at -30° it may be stored for several months. In solution, it slowly decomposes at room temperature, yielding a black, ferromagnetic powder and P(CH3)3. However, the stability in solution may be enhanced by addition of P(CH3)3. Like [(CH3)3P]4Co14 and [(CH3)3P]4Ni,13 the iron compound is very soluble in hydrocarbons and ethers. These solutions are extremely air sensitive, the solid being pyrophoric. The spectroscopic and analytical data and some reactions are reported elsewhere8 9,15 16. The purity is tested by means of the ir spectrum8. Indicative are bands at 1822 V(Fe—H)], 895, and 455 cm-1. Anal. Calcd. for Ci2H36FeP4 C, 40.02 H, 10.08 Fe, 15.51. Found C, 39.61 H, 9.86 Fe, 15.52. 

The four-coordinate sqnare planar iron(n) porphyrins discussed above are not only of great valne in heme protein model chemistry, but also in chemical applications, since they undergo a wealth of ligand addition reactions. For example it has been shown that TPPFe complexes are active catalysts for important carbon transfer reactions in organic chemistry and are found to catalyze the stereoselective cyclopropanation of aUcenes, olefin formation from diazoalkanes, and the efficient and selective olefination of aldehydes and other carbonyl compounds. The active species in these carbon transfer reactions are presumably iron porphyrin carbene complexes. " It was also found that ferrous hemin anchored to Ti02 thin films reduce organic halides, which can pose serious health problems and are of considerable environmental concern because of their prevalence in groundwater. ... 

The Simmons-Smith reaction is an efficient and powerful method for synthesizing cyclopropanes from alkenes [43]. Allylic alcohols are reactive and widely used as substrates, whereas a,j8-unsaturated carbonyl compounds are unreactive. In 1988, Ambler and Davies [44] reported the electrophilic addition of methylene to a,/3-unsaturated acyl ligands attached to the chiral-at-metal iron complex. The reaction of the racemic iron complex 60 with diethylzinc and diiodomethane in the presence of ZnCl2 afforded the c/s-cyclopropane derivatives 61a and 61b in 93 % yield in 24 1 ratio (Sch. 24). 

Like the double bond, the carbon-carbon triple bond is susceptible to many of the common addition reactions. In some cases, such as reduction, hydroboration and acid-catalyzed hydration, it is even more reactive. A very efficient method for the protection of the triple bond is found in the alkynedicobalt hexacarbonyl complexes (.e.g. 117 and 118), readily formed by the reaction of the respective alkyne with dicobalt octacarbonyl. In eneynes this complexation is specific for the triple bond. The remaining alkenes can be reduced with diimide or borane as is illustrated for the ethynylation product (116) of 5-dehydro androsterone in Scheme 107. Alkynic alkenes and alcohols complexed in this way show an increased structural stability. This has been used for the construction of a variety of substituted alkynic compounds uncontaminated by allenic isomers (Scheme 107) and in syntheses of insect pheromones. From the protecting cobalt clusters, the parent alkynes can easily be regenerated by treatment with iron(III) nitrate, ammonium cerium nitrate or trimethylamine A -oxide. ° ... 

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