Iron systems

Bioinorganic applications of m.c.d. spectroscopy copper, rare earth ions, cobalt and non-heme iron systems. D. M. Dooley and J. H. Dawson, Coord. Chem. Rev., 1984, 60,1 (176). 

The graphite-bromine-iron system has also been studied. No stoi-... 

Tarasevich MR, Zhutaeva GV, Bogdanovskaya VA, Radina MV, Ehrenburg MR, Chalykh AE. 2007. Oxygen kinetics and mechanism at electrocatalysts on the base of palladium-iron system. Electrochim Acta 52 5108-5118. 

Several nickel(II) complexes (e.g., (173)-(176)) have successfully been used to catalyze ATRP, especially when coupled with bromo-initiators, although activities are usually lower than with copper, ruthenium or iron systems.416-419 The alkylphosphine complex (175) is thermally more stable than (174) and has been used to polymerize a variety of acrylate monomers between 60 °C and 120 °C.418 Complex (176) is an unusual example of a well-defined zerovalent ATRP catalyst it displays similar activities to the Ni11 complexes, although molecular weight distributions (1.2-1.4) are higher.419 Pd(PPh3)4 has also been investigated and was reported to be less controlled than (176).420... 

Hydrogen Production from Residual Oil Using Steam-Iron System... 

Iron-based catalysts have been used in all the plants constructed after the war, because (a) iron is considerably cheaper than cobalt, (b) iron systems are generally more stable, and (c) greater flexibility with regard to product distribution can be attained. With the exception of the SASOL complex, which will be dealt with in Section I,B, the only Fischer-Tropsch plant of any appreciable size constructed in the West since the... 

The seemingly plausible Scheme shown in 4 is inconsistent with the results of the 13C0 labeling study as are most schemes which do not involve CO insertion for the chain propagation. We believe that ethylene arises from the same sequence of steps as the other hydrocarbon products. The role of the second metal center in the reduction cannot be described. We believe that the iron-iron bond is cleaved early in the reaction since the reduction in the presence of PBu3 produced the unsubstituted species, LiCpFe(C0)2. While there is too little information currently available to assess the importance of Scheme 3, our results on reduction in this iron system are not consistent with the normal CO insertion mechanism or with carbene oligomerization. We suggest Scheme 3 until further research can be accomplished. 

A good example of a concentration cell would be the iron system in the worked example above, in which a(R) = a.cui = U accordingly, for simplicity here, we will assume that the reduced form of the couple is a pure solid. 

Some bacteria possess uptake systems of all the ABC types mentioned in this chapter. For example, the pathogenic microbe H. influenzae is able to sequester iron via siderophore-type systems, ferric iron systems, and metal-type systems. Similarly, strains of Yersinia use multiple routes to take up iron bound to siderophores (e.g. yersiniabactin) and haem, as well as unliganded iron by the ferric-iron-type Yfu system and the metal-type Yfe system. No iron-uptake systems of the ABC transporter type were identified in the genomes of Mycoplasma genitalium and Mycoplasma pneumoniae. In contrast, among the 19 ABC transporters of the related species Ureaplasma urealyticum six presumed different Fe3+ and/or haem transporters were identified [228]. 

Although the preparative chemistry of (vinylketene)cobalt(I) complexes is relatively limited in the literature, the methods used include all the major procedures that have been more widely exploited in the analogous chromium and iron systems. There are many similarities between the intermediates involved in the synthesis of vinylketene complexes of iron, chromium, and cobalt, but as the metal is varied the complexes containing analogous ligands often exhibit significant differences in stability and reactivity (see Sections II and VI). Comparison of such species has often been an important aim of the research in this area. The (vinylketene)cobalt(I) complexes have also been shown to be synthetically useful precursors to a variety of naphthols, 2-furanones, ce-pyrones, phenols,6,22,95 >8, y-unsaturated esters,51 and furans.51,96a... 

Abstract Two systems are discussed in this chapter, which are copper activating zinc-iron system with and without depressants. Firstly, the system in the absence of depressants is discussed. And it is obtained that at a specific pH the activation for each mineral occurs in a certain range. Through the electrochemical methods and surface analysis the entity contributing to the activation can be identified which are usually copper sulphides and vary for different minerals. Secondly, the system with depressants is researched. And also the effects of pulp potential on the activation are discussed. The same conclusion can be obtained as the one from the former system. Furthermore, zeta potential are involved in the discussion of activation and die mechanism can be explained firom the changes of zeta potential. Similarly, the activation mechanism of this system is also studied through solution chemistry, bonding of activator with mineral surfaces and surface analysis. 

Review work for future updates of our data base should focus on iron compounds and complexes. The iron system is thought to be of crucial importance for characterizing the redox behaviour of radioactive waste repositories. Preliminary applications have indicated that the lack of data for the iron system is a source of major uncertainties associated with the definition of an oxidation potential. Hence, there is little use in developing sophisticated redox models for radionuclides as long as the dominant redox processes in a repository are poorly known. 

The apparent pH of the neutral solution, in this case Fe(OH)3 in 878 water molecules, can be obtained by taking the observed ratios of the hydrolysis species, for example, for the iron system, the pKa for the first hydrolysis reaction... 

Recent work by Ford et al. demonstrates that a variety of metal carbonyl clusters are active catalysts for the water-gas shift under the same reaction conditions used with the ruthenium cluster (104a). In particular, the mixed metal compound H2FeRu3(CO)13 forms a catalyst system much more active than would be expected from the activities of the iron or ruthenium systems alone. The source of the synergetic behavior of the iron/ruthenium mixtures is under investigation. The ruthenium and ruthenium/iron systems are also active when piperidine is used as the base, and in solutions made acidic with H2S04 as well. Whether there are strong mechanistic similarities between the acidic and basic systems remains to be determined. 

It may be concluded that the steric bulk of the alkyl substituents (R) is an extremely important factor in stabilizing the various coordination modes and thus steers the course of the reactions. However, the tendency to form metal-metal bonds and the electronic influence of R may also be important. In this respect it is of interest that in the case of the analogous iron systems the number of products is much smaller. For example Fe2(CO)9 reacts with R-DAB according to equations (8) and (9). 

While the potential for these species in nucleophile substitution for chloride has been demonstrated, the processes have not been fully developed nor applied. The two-stage process of addition-substitution for chloride and arene detachment is exemplified for the iron system in equation (21). 

While the reaction thermodynamics is important, the reaction kinetics is equally important in designing zero-valent iron system furthermore, the... 

Copper in its high oxidation state [Cu(III), formed in the reaction of Cu2+ with -OH] releases OH in acid media (Meyerstein 1971 Cohen et al. 1990 Ulanski and von Sonntag 2000). Thus, it can also not be fully excluded also in the iron system a very short-lived Fe(I V) species is an intermediate on the way to OH. 

These differences in the reaction conditions and the stereochemical results of the transesterification of the related manganese and iron systems of Eqs. (2) and (8) are explained on the basis of the results of the following reaction. 

Grundl, T. and D. Macalady. 1989. Electrode measurement of redox potential in anaerobic aqueous iron systems. J. Contam. Hydrol. 5, 97-117. 

A general kinetic model should accommodate all chemical processes known to affect the dechlorination process. These include (1) reductive dechlorination takes place on the iron surface, rather than in the aqueous phase, so adsorption must occur (2) other components in the system may affect the dechlorination reaction by competing for the reaction sites (3) surface sites for reduction and for sorption may not be the same, as for the system with PCE and TCE where dechlorination takes place on the reactive sites, but most of the adsorption is clearly on the nonreactive sites (Burris et al., 1995). In the following section we will first discuss a single-site model similar to the one used by Johnson et al. (1998), which has accounted for the first two observations, then develop a two-site model that will also take the third observation into consideration. We aim to illustrate how coadsorbates in the iron system will affect adsorption and reduction of chlorinated solvents. TCE will be used as an example since relevant adsorption and reduction data are available, from which the required parameters for simulation could be estimated. 

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