Carbonyl iron catalysis

Another noncatalytic step proposed by King et al. (18) in iron carbonyl/base catalysis of the WGSR involves the formation of formate ion however, we recently observed that formate formation appears to have little importance in the related rhodium catalysis of hydrohydroxymethylation. We plan to perform studies of the CO + KOH and C02 + KOH reactions independent of catalysis to more fully appreciate the relationship of these reactions to solution pH and thus the catalytic activity. 

The substituent R may be alkyl, cydoalkyt. or benzyl. Catalysts are selected from transition metals which can form carbonyl complexes. Ruthenium and especially cobalt form active catalysts, although other metals like Rh. Pd. Ft. Os, Ir, Cr, Mn, Fe, and Nt have also been examined. If metals like ruthenium or iron catalysis are used, carbon dioxide is formed instead of water as the by-product. 

Our studies have focussed largely on the catalysis of the shift reaction by ruthenium carbonyl and by the ruthenium carbonyl/iron carbonyl mixtures in the presence of organic amines under low pressures of CO. Representative studies are indicated in Table II where it is notable that ruthenium alone is a considerably better catalyst than is iron alone. Among the ruthenium systems, pyridine solutions are somewhat more... 

Recent developments on iron catalysis have shown the enormous potential of this metal in the reduction of carbonyl groups with hydrogen or using transfer hydrogen and silanes as reducing agents [69]. However, the use of well-defined iron-NHC complexes as catalysts for these reduction processes is rather undeveloped [72]. 

Apart from catalysis with well-defined iron complexes a variety of efficient catalytic transformations using cheap and easily available Fe(+2) or Fe(+3) salts or Fe(0)-carbonyls as precatalysts have been pubhshed. These reactions may on first sight not be catalyzed by ferrate complexes (cf. Sect. 1), but as they are performed under reducing conditions ferrate intermediates as catalytically active species cannot be excluded. Although the exact nature of the low-valent catalytic species remains unclear, some of these interesting transformations are discussed in this section. 

Iron carbonyls have been also used to fabricate nanostructures of potential use in catalysis. In this context, the preparation at room temperature of nano-sized a-Fe single crystals over carbon micro-grid films has been reported. The particles were prepared by electron beam induced deposition using Fe(CO)s as precursor [77]. The use of a focused electron beam to induce metal deposition from carbonyl compounds opens a new route for the preparation of nano-sized metal particles. 

Iron pentacarbonyl is the most important carbonyl compound of iron. It is used primarily to produce finely divided iron metal. Other apphcations are in catalysis of organic reactions in ceramics as an anti-knock in gasohne and in production of red iron oxide pigment. Other carbonyls of iron have very few commercial apphcations. 

Cyclic amino-carbenes, in molybdenum carbonyls, 5, 457 Cyclic bis(phosphine) dichlorides, with iron carbonyls, 6, 48 Cyclic carbenes, as gold atom ligands, 2, 289 Cyclic carbometallation, zirconium complexes, 10, 276 Cyclic carbozirconation characteristics, 10, 276 intermolecular reactions, 10, 278 intramolecular reactions, 10, 278 Cyclic dinuclear ylides, and gold , 2, 276 Cyclic 1,2-diols, intramolecular coupling to, 11, 51 Cyclic enones, diastereoselective cuprate additions, 9, 515 Cyclic esters, ring-opening polymerization, via lanthanide catalysis, 4, 145 Cyclic ethers... 

Heterometal alkoxide precursors, for ceramics, 12, 60-61 Heterometal chalcogenides, synthesis, 12, 62 Heterometal cubanes, as metal-organic precursor, 12, 39 Heterometallic alkenes, with platinum, 8, 639 Heterometallic alkynes, with platinum, models, 8, 650 Heterometallic clusters as heterogeneous catalyst precursors, 12, 767 in homogeneous catalysis, 12, 761 with Ni—M and Ni-C cr-bonded complexes, 8, 115 Heterometallic complexes with arene chromium carbonyls, 5, 259 bridged chromium isonitriles, 5, 274 with cyclopentadienyl hydride niobium moieties, 5, 72 with ruthenium—osmium, overview, 6, 1045—1116 with tungsten carbonyls, 5, 702 Heterometallic dimers, palladium complexes, 8, 210 Heterometallic iron-containing compounds cluster compounds, 6, 331 dinuclear compounds, 6, 319 overview, 6, 319-352... 

The first experiments which were carried out in the author s laboratory on organometallic phase-transfer catalysis were concerned with the reduction of nitrobenzenes (4) to anilines (5) by triiron dodecacarbonyl. Such a conversion was reported to occur in benzene containing methanol at reflux for 10-17 h, with the hydridoundecacarbonyltriferrate anion as the likely key intermediate (16). It was our expectation that the trinuclear iron hydride should be generated by phase-transfer catalysis and if so, effect reduction of nitro compounds (4) under exceedingly mild conditions. Indeed this was the case, as illustrated by the results shown in Table I (17). Not only is the reaction complete in 2 h or less using sodium hydroxide as the aqueous phase, benzene as the organic phase, and benzyltrieth-ylammonium chloride as the phase-transfer catalyst, but it occurs at room temperature and requires less metal carbonyl than when the reaction was... 

The hydride iron carbonyl anion, [HFe(CO)4] , has a structure that is best described as a distorted tbp with the hydride ligand occupying an axial site. The anion is fluxional both in solution and in the solid state.113 The main use is found in organic synthesis and catalysis.114 A typical reaction is the reduction of olefins... 

The shapc-selective catalysis by metal carbonyls deposited in Y zeolites has also been studied by Ballivet-Tkalchenko and Tkaichenko [47. 1351-Iron, cobalt and ruthenium carbonyls in the supercages of acidic and neutral Y zeolites were examined. The product distributirm i limited to the range Ci C9. Fc3(CO)i3 on Na Y zeolite is an active catalyst, whereas Fe3(CO)i2- HY is inactive. However, the addition of the acidic HY zeolite to the Fc3(CO)ii-Y... 

Carbonylation Processes by Homogeneous Catalysis Coordination Chemistry History Coordination Numbers Geometries Iron Organometallic Chemistry Manganese Organometallic Chemistry Nickel Organometallic Chemistry Rhodium Organometallic Chemistry. 

Certain classical coordination complexes (see Coordination Complexes) of iron (e.g. Prussian blue) will be dealt with in other articles (see Iron Inorganic Coordination Chemistry and Cyanide Complexes of the Transition Metals), as will much of the chemistries of iron carbonyls (see Metal Carbonyls) and iron hydrides (see Hydrides) (see Carbonyl Complexes of the Transition Metals Transition Metal Carbonyls Infrared Spectra, and Hydride Complexes of the Transition Metals). The use of organoiron complexes as catalysts (see Catalysis) in organic transformations will be mentioned but will primarily be covered elsewhere (see Asymmetric Synthesis by Homogeneous Catalysis, and Organic Synthesis using Transition Metal Carbonyl Complexes). 

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