Iron carbonyl, as catalyst

Branchadell, V., Crevisy, C., Gree, R., From Allylic Alcohols to Aldols by Using Iron Carbonyls as Catalysts Computational Study on a Novel Tandem Isomerization Aldolization Reaction, Chem. Eur. J. 2004, 10, 5795 5803. 

Reduction of the ketones cyclohexanone, / -chloroacetophenone, acetophenone, butanone, and /7-methylacetophenone by phase transfer catalysis with the application of [NMe(C8Hi7)3]Cl, [NEt3(CH2Ph)]Cl, and 18-crown-6 as phase transfer agents and isopropanol and 1-phenylethanol as hydrogen donors as well as iron carbonyls as catalysts, represents a very interesting reaction. 

Under the same reaction conditions with slightly increased temperatures (110-170 °C) and iron carbonyl as catalyst, p-quinone was found to be the main reaction product [402]. If the same reaction is carried out with a slightly increased amount of water hydroquinone is obtained in good yields [399, 400, 402]. As with the conversion of acetylene with carbon monoxide and a third component, in the reaction of ethylene, carbon monoxide and water or alcohol, different reaction products may also be obtained by altering the reaction conditions and catalysts. 

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... 

Most examples in the literature on hydrosilylation with iron complexes as catalyst concern Fe(CO)5 or related iron carbonyl compounds [41]. The first use of iron pentacarbonyl was reported for the reaction of silicon hydrides with alkenes at 100-140 °C to form saturated and unsaturated silanes according to Scheme 4.20 [42, 43]. 

It may be considered ironic that as early as 1969 a nearly complete description of the characteristic features of the subsequently presented LPO technology had been published by Monsanto researchers [5]. The company decided at that stage not to deal with hydroformylation any longer, but instead they concentrated on the development of the nowadays well-known acetic acid process (using modified rhodium carbonyl as catalyst) (cf. Section 2.1.2.1) [6]. 

In around 1925, the Fisher-Tropsh process, which synthesizes mainly liquid hydrocarbons by the reaction of carbon monoxide with hydrogen at 180-300 C and under 1—300 atm in the presence of nickel, cobalt and iron compounds as catalysts, was developed [81,81a,81b]. This process was used as the process for synthetic petroleum in Germany. However, at present, the production has been continued only in South Africa as state policy. This reaction is revealed to have the action of metal carbonyls as intermediates of the catalysts. In 1938, Roden [82] developed the 0X0 process which produced aldehydes by the reaction of olefins with carbon monoxide and hydrogen in the presence of cobaltcarbonyl type catalysts. 

Iron hydrocarbonyl has been repeatedly reported to be an active hydro-formylation catalyst [165, 166]. Some papers state that it is active at a lower pressure than cobalt [23, 165, 166, 168-170]. However, in a recent paper it was shown that iron hydrocarbonyl is only 1 10 times as active as Co carbonyl [824, 980]. Other authors recommend adding iron carbonyl as a promoter to Co catalysts [171, 979]. 

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). 

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... 

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]. 

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]. 

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. 

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). 

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