Iron-carbonyl catalyst

Rhodium and cobalt carbonyls have long been known as thermally active hydroformylation catalysts. With thermal activation alone, however, they require higher temperatures and pressures than in the photocatalytic reaction. Iron carbonyl, on the other hand, is a poor hydroformylation catalyst at all temperatures under thermal activation. When irradiated under synthesis gas at 100 atm, the iron carbonyl catalyzes the hydroformylation of terminal olefins even at room temperatures, as was first discovered by P. Krusic. ESR studies suggested the formation of HFe9(C0) radicals as the active catalyst, /25, 26/. Our own results support this idea, 111,28/. Light is necessary to start the hydroformylation of 1-octene with the iron carbonyl catalyst. Once initiated, the reaction proceeds even in the... 

In 1993, Murai s group examined the effectiveness of the iron-triad carbonyl complexes Fe(CO)5, Fe2(CO)9 and Fe3(CO)12 as catalysts for the reaction of styrene with triethylsilane [47]. Whereas Fe(CO)5 showed no catalytic activity, Fe2(CO)9 and Fe3(CO)12 formed selectively P-silylstyrene 57a and ethylbenzene 58. Interestingly, Fe3(CO)12 is the catalyst that exhibited the highest selectivity. This trinuclear iron carbonyl catalyst was also successfully applied in the reaction of different para-substituted styrenes with Et3SiH giving only the (E)-P-triethylstyrenes in 66-70% yield (Scheme 4.23). 

A very pronounced synergistic effect is found for binary ruthenium-iron carbonyl catalysts in the water-gas shift reaction. Both mixed ruthenium-iron clusters and mixtures of ruthenium clusters with iron complexes are considerably more active in basic solutions. Whereas the water-gas shift activity (moles of H2 per mole of complex per day) of alkaline aqueous ethoxyethanol solutions of Ru3(CO)12 and Fe(CO)j is... 

In basic solution Fe(CO)6 and M(CO) (M = Cr, Mo, or W) catalyse the water-gas shift reaction (i.e. HgO + C0 C02 + H2). Ruthenium carbonyl compounds catalyse this reaction in both basic and acidic media mixed ruthenium-iron carbonyl catalysts e.g. [FeRu3H2(CO) 3] are considerably more active in basic solution than either ruthenium or iron carbonyls alone. [PtLg] (activity L = PPr 3>PEt3>PPh3) and KaPtCl4-SnCl4,5H20 also catalyse the water-gas shift reaction the proposed mechanism for the latter catalyst is shown in Scheme 1. ... 

Chromium. The complexes Cr(arene)(CO)s are highly selective catalysts for the hydrogenation of dienes to monoenes. A recent study concentrated on the reduction of methyl hexa-2,4-dienoate (sorbate), and the mechanism was found to be similar to that for reaction with iron-carbonyl catalysts. It does not involve rate-determining loss of the arene to give Cr(CO>3 as the active species, as suggested earlier for a different catalytic system, but rather the arene becoming bi- or uni- rather than ter-dentate, so that the diene can be co-ordinated ... 

Reactions of acetylene and iron carbonyls can yield benzene derivatives, quinones, cyclopentadienes, and a variety of heterocycHc compounds. The cyclization reaction is useful for preparing substituted benzenes. The reaction of / fZ-butylacetylene in the presence of Co2(CO)g as the catalyst yields l,2,4-tri-/ f2 butylbenzene (142). The reaction of Fe(CO) and diphenylacetylene yields no less than seven different species. A cyclobutadiene derivative [31811 -56-0] is the most important (143—145). 

Dr. Moeller In our plant, we investigated our catalyst after 4000 and 5000 hrs of operation and we found no trace of iron on our catalysts. But we know that if you take no precautions against iron carbonyl formation, then you will destroy some part of your activity by iron deposition on your catalyst. And we found that the iron carbonyl is formed mainly at the mild steel tube walls or at the tube in the temperature range of 150°-200°C. So, if you enter this range and you have to heat up your gas, which has a high CO content and steam in it, you have to... 

Feed gases were controlled by Brooks 5850 series E mass flow controllers. Iron carbonyl traps consisting of lead oxide on alumina (Calsicat) were placed on the CO gas line. All gas lines were filtered with Supelco 02/moisture traps. Catalysts were activated with H2 N2 (100 cm3/min 130 cm3/min) at 300°C, purged in N2 (130 cm3/min), and cooled to a temperature of interest in N2 to obtain background scans. For CO adsorption measurements, CO N2 (3.75 cm3/min 130 cm3/min) was flowed at 300°C and then cooled to the temperature of interest. Following CO adsorption experiments, steady-state water-gas shift measurements were carried out at either 225 or 185°C, using C0 H20 N2 (3.75 cm3/min 62.5 cm3/min 67.5 cm3/min) or C0 H20 H2 (same ratio). 

King and coworkers—formate intermediates and a kinetic approach over Cr and other Group VIb carbonyl catalysts. Like Pettit and coworkers,18 34 King et a/.25,3 J 42,43,54,59,138,155 also studied water-gas shift on mononuclear carbonyls of iron and, in a detailed investigation, indicated that Scheme 7 of Pettit et al,34 was... 

The present paper focuses on the interactions between iron and titania for samples prepared via the thermal decomposition of iron pentacarbonyl. (The results of ammonia synthesis studies over these samples have been reported elsewhere (4).) Since it has been reported that standard impregnation techniques cannot be used to prepare highly dispersed iron on titania (4), the use of iron carbonyl decomposition provides a potentially important catalyst preparation route. Studies of the decomposition process as a function of temperature are pertinent to the genesis of such Fe/Ti02 catalysts. For example, these studies are necessary to determine the state and dispersion of iron after the various activation or pretreatment steps. Moreover, such studies are required to understand the catalytic and adsorptive properties of these materials after partial decomposition, complete decarbonylation or hydrogen reduction. In short, Mossbauer spectroscopy was used in this study to monitor the state of iron in catalysts prepared by the decomposition of iron carbonyl. Complementary information about the amount of carbon monoxide associated with iron was provided by volumetric measurements. 

The evolution of the initial surface species in several oxides was studied early on [72, 73] the first studies already indicated that catalysts derived from iron carbonyls can be more than one order of magnitude more dispersed than catalysts prepared by conventional techniques using salts of Fe as precursors [72]. 

Several factors must be taken into account when the dispersion of iron catalysts prepared by carbonyl complexes is compared to that of conventionally prepared catalysts. The iron loading and the possible formation of irreducible iron phases (by the interaction of Fe or Fe with the support) can determine a low reduction degree for conventionally prepared catalysts with low iron content and a support with high ability to react with the iron cations. In contrast, when catalysts prepared from carbonyl complexes are considered, for a given support the temperature of pre treatment which defines the hydroxyl population of the surface is a main aspect to be taken into account. For Fe/Al203 catalysts prepared from iron carbonyls and reduced after impregnation at a moderate temperature (573 K), the extent of... 

The ease of oxidahon of the surface iron carbonyl species has been shown in the preparation of Fe/MCM-41 catalysts. A method of preparation with ultrasound that led to subcarbonyl confined species in the case of Cr, Mn or Co catalysts rendered Fe203 when Fe2(CO)9 was used as precursor [23]. 

A similar addition to alkynes results in the formation of the corresponding unsaturated acids and derivatives.14,23,121-124 Cobalt, nickel, and iron carbonyls, as well as palladium complexes, are the most often used catalysts.14... 

More recently another report on the catalytic conversion of C02, H2, and alcohols into formate esters has appeared (160a). This work uses as catalysts the anionic iron carbonyls HFe(CO)4" and HFe CO), and reports modest conversions to alkyl formates under conditions of elevated pressure and temperature. 

The phenomenon of metal transport via the creation of volatile metal carbonyls is familiar to workers using carbon monoxide as a reactant. It is often found that carbon monoxide is contaminated with iron pentacarbonyl, formed by interactions between carbon monoxide and the walls of a steel container. Thus, it is common practice to place a hot trap between the source of the CO and the reaction vessel. Iron carbonyl decomposes in the hot trap and never reaches the catalyst that it would otherwise contaminate or poison. Transport of a number of transition metals via volatile metal carbonyls is common. For example, Collman et al. (73) found that rhodium from rhodium particles supported on either a polymeric support or on alumina could be volatilized to form rhodium carbonyls in flowing CO. 

In an earlier related study, Evans and Newell (112) demonstrated the anionic iron carbonyl hydrides [HFe3(CO),][PNP] and [HFe(CO)4][PNP] to be catalytically active for this reaction, generating yields no greater than 5.8 1 moles of formate per mole of catalyst precursor. The low yields were attributed to catalyst degradation caused by oxidation by carbon dioxide as evidenced by the detection of carbonates in the system. 

Exclusive formation of silylstyrenes 76 is achieved when the reactions of styrene and 4-substituted styrenes with HSiEt3 are catalyzed by Fe3(CO)i2 or Fe2(CO)9100. Other iron-triad metal carbonyl clusters, Ru3(CO)i2 and Os3(CO)i2, are also highly active catalysts, but a trace amount of hydrosilylation product 77 is detected in the Ru-catalyzed reactions and the Os-catalyzed reactions are accompanied by 3-12% of 77 (equation 31)100. Mononuclear iron carbonyl, Fe(CO)5, is found to be inactive in this reaction100. 

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