Cobalt-iron-system

Nis] Nishizawa, T., Ishida, K., The Co-Fe (Cobalt-Iron) System , Bull. Alloy Phase Diagrams, 5(3), 250-259 (1984) (Crys. Structure, Phase Diagram, Review, Thermodyn., 129) [1985Sch] Schmid, R., Musbah, O., Chang, Y.A., Phase Relations and Thermodynamics of the Fe-Co-S System at 1073 K , Z. Metallkd., 76(1), 1-6 (1985) (Experimental, Phase Diagram, Thermodyn.,, , 17)... 

Basic oxides of metals such as Co, Mn, Fe, and Cu catalyze the decomposition of chlorate by lowering the decomposition temperature. Consequendy, less fuel is needed and the reaction continues at a lower temperature. Cobalt metal, which forms the basic oxide in situ, lowers the decomposition of pure sodium chlorate from 478 to 280°C while serving as fuel (6,7). Composition of a cobalt-fueled system, compared with an iron-fueled system, is 90 wt % NaClO, 4 wt % Co, and 6 wt % glass fiber vs 86% NaClO, 4% Fe, 6% glass fiber, and 4% BaO. Initiation of the former is at 270°C, compared to 370°C for the iron-fueled candle. Cobalt hydroxide produces a more pronounced lowering of the decomposition temperature than the metal alone, although the water produced by decomposition of the hydroxide to form the oxide is thought to increase chlorine contaminate levels. Alkaline earths and transition-metal ferrates also have catalytic activity and improve chlorine retention (8). 

Earlier catalysts were based on cobalt, iron, and nickel. However, recent catalytic systems involve rhodium compounds promoted by methyl iodide and lithium iodide (48,49). Higher mol wt alkyl esters do not show any particular abiUty to undergo carbonylation to anhydrides. 

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). 

Christokova St. G., Stoyanova M., and Georgieva M. 2001. Low-temperature iron-modified cobalt oxide system. Part 1. Preparation and characterisation. Appl. Catal. A Gen. 208 235 2. 

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... 

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... 

CRYSTAL PHASES (a-, f, y, tj, etc.). Certain alloy systems may form different crystal structures, according to the relative proportions of the constituents, e.g., Cu-Zn. for which no less than five different phases are known. In many cases, the same crystal structure occurs with quite different constituent metals, so that it is often possible to use one expression such, for example, as 0-phase, to cover a wide variety of compounds all having the same basic structure. This effect is explained hy the Hume-Rother rules. Pure substances, as well as alloys, may exhibit more than one crystal structure, depending on temperature and past history, e.g.. cobalt, iron, titanium. 

Shortly after the introduction of the bismuth molybdate catalysts, SOHIO developed and commercialized an even more selective catalyst, the uranium antimonate system (4). At about the same time, Distillers Company, Ltd. developed an oxidation catalyst which was a combination of tin and antimony oxides (5). These earlier catalyst systems have essentially been replaced on a commercial scale by multicomponent catalysts which were introduced in 1970 by SOHIO. As their name implies, these catalysts contain a number of elements, the most commonly reported being nickel, cobalt, iron, bismuth, molybdenum, potassium, manganese, and silica (6-8). 

As in the cobalt system, the reaction generates significant quantities of CH4 as a by-product (in some cases, the methane is the major product). The selectivity of homologated alcohol to hydrocarbon appears to be independent of the partial pressures of either CO or H2 127), and the authors suggest that this could be attributable, at least in the Mn system, to the relative rates of methyl migration to homolytic bond dissociation. In the iron system, methane is generated by simple reductive elimination from the HFe(CH3)(CO)4 intermediate. 

A chemistry of cobalt-sulfide-thiolate molecular clusters comparable with that of iron systems has also begun to emerge. Treatment of [Co4( -SPh)6(SPh)4]2- with HS- in acetone affords the octanuclear cluster [Co8(ji4-S)6(SPh)8]4 isolated as its Pr4N+ salt.988 In MeCN solution the complex is red-purple with intense sulfur-core charge transfer bands which obscure the Co" d-d transitions. This behaviour contrasts with that of both mono- and poly-nuclear cobalt"-thiolate complexes, which all display LMCT bands below 440 nm and have well-developed v2 and v3 features. The [Co8(/j4-S6)]4+ core sustains reversible one-electron oxidation and reduction (E]l2 = —0.54, — 1.18 V, MeCN) and chemical reduction with sodium acenaphthylenide in THF gives [Co8(/r4-... 

Redox-active metals are the initiators of perhaps greatest importance for lipid oxidation in oils, foods, and biological systems because they are ubiquitous and active in many forms, and trace quantities (electron transfers appear to be active catalysts these include cobalt, iron, copper, manganese, magnesium, and... 

Benzene, benzene-d , and fluorobenzene were found (770, 777) to react with chromium, cobalt, iron, and nickel atoms on codeposition in the neat ligand at 77 K, or in argon matrices at 10-12 K. IR studies of the products indicated that the initial reaction of these transition-metal atoms with an aromatic system is 7r-complex formation. Studies of ligand concentration-effects showed that the chromium-atom reaction is approximately second-order with respect to benzene, yielding the previously known (782) complex (CeH6)2Cr, whereas, with the other metals, the reaction is first-order, yielding MfCsHs), M = Co, Fe, or Ni. The absence of CrfCeH ) is probably a reflection of (a) the fact that the... 

Not only pure aluminum, but also aluminum alloys can be electrodeposited from organic electrolyte systems. Thus, codeposition of iron, nickel, and cobalt from systems composed of AlBrj, LiBr, and toluene have been reported. However, only a small content up to a maximum of 1.4% (for instance, iron) is reached [175]. 

Amidocarbonylation is a recently developed, organometallic-catalyzed route to amino acid generation - particularly A(-acyl a-amino acids - using either aldehydes or alkenes as starting materials and synthesis gas as an integral building block. The two principal classes of reaction are illustrated in eqs. (1) and (2). Both syntheses offer the opportunity to introduce two functionalities, amido and carboxylate, simultaneously where an amide is the co-reactant. Homogeneous amidocarbonylation catalysts are typically cobalt carbonyl-based, or utilize transition-metal binary systems, e. g. cobalt-rhodium, cobalt-palladium, and cobalt-iron. 

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