Iron-cobalt carbonyl catalyst

Entrapment of the ionic iron-cobalt carbonyl compounds [(C2Hs)4N +-[FeCo3(CO)i2] (Low, 1990) in silica sol-gel, completely retains the structural features of the homogeneous complex. The entrapped cluster proved to be a stable and recyclable catalyst for quantitative transformation of norbomadiene selectively into dodecahydro-l,2,4 5,6,8-dimetheno-r-indecene ( binor-S ) (Scheme 24-3) (Blum, 2000). 

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... 

Fischer-Tropsch synthesis could be "tailored by the use of iron, cobalt and ruthenium carbonyl complexes deposited on faujasite Y-type zeolite as starting materials for the preparation of catalysts. Short chain hydrocarbons, i.e. in the C-j-Cq range are obtained. It appears that the formation and the stabilization of small metallic aggregates into the zeolite supercage are the prerequisite to induce a chain length limitation in the hydrocondensation of carbon monoxide. However, the control of this selectivity through either a definite particle size of the metal or a shape selectivity of the zeolite is still a matter of speculation. Further work is needed to solve this dilemna. 

Transition metal complexes which react with diazoalkanes to yield carbene complexes can be catalysts for diazodecomposition (see Section 4.1). In addition to the requirements mentioned above (free coordination site, electrophi-licity), transition metal complexes can catalyze the decomposition of diazoalkanes if the corresponding carbene complexes are capable of transferring the carbene fragment to a substrate with simultaneous regeneration of the original complex. Metal carbonyls of chromium, iron, cobalt, nickel, molybdenum, and tungsten all catalyze the decomposition of diazomethane [493]. Other related catalysts are (CO)5W=C(OMe)Ph [509], [Cp(CO)2Fe(THF)][BF4] [510,511], and (CO)5Cr(COD) [52,512]. These compounds are sufficiently electrophilic to catalyze the decomposition of weakly nucleophilic, acceptor-substituted diazoalkanes. 

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... 

Although nickel i the prefer red metal for alkyne carbonylation, catalysts based on cobalt, rhodium, iron, ruthenium, and palladium are preferred for the carbonylation of alkenes, The common intermediate is an acyl-metal species formed by the ligand migration sequence... 

Cobalt catalysts were used for substitution reactions of organic halides [442] and a small-ring enol lactone [Eq. (201) 443]. The cobalt salt seems to be the most effective one among a few transition metal salts involving copper, nickel, [see Eq. (130)], and iron. Without the catalyst, Grignard reagent attacked the carbonyl carbon of the enol lactone to give a mixture of a few ketonic compounds in a low yield. 

Some insight into the mechanisms of the iodine-promoted carbonylation has been obtained by radioactive tracer techniques [17] and low-temperature NMR spectroscopy [18]. The mechanism involves the formation of HI, which in a series of reactions forms with rhodium a hydrido iodo complex which reacts with ethylene to give an ethyl complex. Carbonylation and reductive elimination yield propionic acid iodide. The acid itself is then obtained after hydrolysis. The rate of carboxylation was reported to be accelerated by the addition of minor amounts of iron, cobalt, or manganese iodide [19]. The rhodium catalyst can be stabilized by triphenyl phosphite [20]. However, it is doubtful whether the ligand itself would meet the requirements of an industrial-scale process. 

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. 

Alkyne cyclotrimerization occurs at various homogeneous and heterogeneous transition metal and Ziegler-type catalysts [7], Substituted benzenes have been prepared in the presence of iron, cobalt, and nickel carbonyls [8] as well as trialkyl- and triarylchromium compounds [9]. Bis(acrylonitrile)nickel [10] and bis(benzonitrile)palladium chloride [11] catalyze the cyclotrimerization of tolane to hexaphenylbenzene. NiCl2 reduced by NaBH4 has been utilized for the trimer-ization of 3-hexyne to hexaethylbenzene [12]. Ta2Cl6(tetrahydrothiophene)3 and Nb2Cl6(tetrahydrothiophene)3 as well as 7 -Ind-, and 77 -Ru-rhodium... 

The carbonylation of a benzyl halide in the presence of iron pentacarbonyl to give a phenylacetic acid may serve to exemplify the interaction of a metal carbonyl, carbon monoxide, PT catalyst, aqueous sodium hydroxide, and the substrate [79]. Fe(CO)5 is attacked by QOH at the interphase, and the species formed is extracted into the depths of the oganic phase, where it reacts with CO and benzyl halide (Eqs. 13 and 14). This new anion 3 is the actual catalyst. It reacts with a second benzyl halide to give a non-ionic intermediate 4 (Eq. 15). By insertion of CO and attack of QOH, 4 is decomposed to the reaction product under regeneration of 3 (Eq. 16). Thus, the action of the PT catalyst is twofold. Firstly it transports the metal carbonyl anion. More important seems to be its involvement in the (rate-determining) decomposition step. A basically similar mechanism was proposed for cobalt carbonyl reactions [80], which have been modified somewhat quite recently (see below). 

Hydrocarboxylation is the formal addition of hydrogen and a carboxylic group to double or triple bonds to form carboxylic acids or their derivatives. It is achieved by transition metal catalyzed conversion of unsaturated substrates with carbon monoxide in the presence of water, alcohols, or other acidic reagents. Ester formation is also called hydroesterification or hydrocarb(o)alkoxylation . The transition metal catalyst precursors are nickel, iron or cobalt carbonyls or salts of nickel, iron, cobalt, rhodium, palladium, platinum, or other metals4 5. 

Carbohalogenation of various terminal or internal alkynes, via addition of perfluoroalkyl iodides or bomides, is catalyzed by carbonyl complexes of iron, cobalt or ruthenium. In this case, dichlorotris(triphenylphosphane)ruthenium(II) is not active as a catalyst. rram-Addition products are usually obtained in good yield under mild reaction conditions36. 

In spite of the differences in the electronic configuration of iron, cobalt, and nickel, the manner in which their respective carbonyls function as catalysts is essentially the same, differing only in detail. Under the proper conditions, for example, any of these metal carbonyls catalyze the reaction of acetylene, carbon monoxide, and alcohols to form acrylates. An iron complex, XI, in which most of the terminal carbonyls have been replaced by cyclopentadienyl groups, has been found to function, hke dicobalt octa-carbonyl, as a homogeneous hydrogenation catalyst 16) ... 

Homogeneous organometallic catalysts such as iron and cobalt carbonyls and rhodium complexes effect double-bond migration as do some metals and their oxides, sulphur dioxide and iodine. 

Besides the mentioned catalysts, the other transition metals were also appUed in carbonylation of nitro compounds by various groups [71-79]. Such as nickel, osmium, iron, cobalt, and molybdenum. All the expected products were produced by the carbonylation of nitro compounds. Interestingly, anilines were produced from nitroarenes in the presence of Mo(CO)e and DBU under microwave irradiation in moderate to excellent yields (Scheme 9.7). 

The heptanuclear iron carbonyl cluster [Fe3(CO)u(/u-H)]2-Fe(DMF)4 (178) acted as an efficient catalyst in the reduction of carboxamides by l,2-bis(dimethylsilyl)benzene in toluene to the corresponding amines in high yields. Several tertiary and secondary amides including a sterically crowded amide were also reduced smoothly A review of the development of optically active cobalt complex catalysts for enan-tioselective synthetic reactions has addressed the applications of ketoiminatocobalt(II) complexes such as (5)-MPAC (179) and (5)-AMAC (180), transition-state models for borohydride reduction, halogen-free reduction by cobalt-carbene complexes. 

Cobalt, nickel, iron, ruthenium, and rhodium carbonyls as well as palladium complexes are catalysts for hydrocarboxylation reactions and therefore reactions of olefins and acetylenes with CO and water, and also other carbonylation reactions. Analogously to hydroformylation reactions, better catalytic properties are shown by metal hydrido carbonyls having strong acidic properties. As in hydroformylation reactions, phosphine-carbonyl complexes of these metals are particularly active. Solvents for such reactions are alcohols, ketones, esters, pyridine, and acidic aqueous solutions. Stoichiometric carbonylation reaction by means of [Ni(CO)4] proceeds at atmospheric pressure at 308-353 K. In the presence of catalytic amounts of nickel carbonyl, this reaction is carried out at 390-490 K and 3 MPa. In the case of carbonylation which utilizes catalytic amounts of cobalt carbonyl, higher temperatures (up to 530 K) and higher pressures (3-90 MPa) are applied. Alkoxylcarbonylation reactions generally proceed under more drastic conditions than corresponding hydrocarboxylation reactions. 

The products of cyclocarbonylation find application in the pharmaceutical industry as well as in the chemical industry, for example, as solvents. The best catalysts for this reaction are cobalt carbonyls however, carbonyls of rhodium and iron and palladium complexes have also been utilized. Sometimes nickel carbonyl may also be used, although it is less active in this type of reaction. Aromatic and aliphatic hydrocarbons as well as cyclic ethers are used as solvents. Reactions are carried out at 390-570 K and 10-30 MPa. 

A quite different process, called Reppe carbonylation, has been used to convert acetylene to acrylic acid esters. The catalysts are carbonyls of iron, cobalt or nickel and the hydrogen source is a hydrogen halide, HX. The process is thought to involve oxidative addition of HX to the metal carbonyl, followed by coordination and insertion of alkyne into the M—H bond and insertion of CO into the M—C bond. The resulting acyl complex is cleaved by alcohol to produce the ester and the metal hydride catalyst. De Angelis et al. have reported a theoretical analysis of the Ni(CO)4 system. 

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. 

Besides nickel and cobalt, almost all of the catalysts discussed in the last chapter which were suited for the formation of free acids can be applied, e. g. rhodium, palladium and, with certain restrictions, iron. Cobalt hydrocarbonyl catalyzes the stoichiometric ester synthesis at mild reaction conditions [35, 121]. The initially formed acylcobalt carbonyls react rapidly with alcohols even at 50 °C and, in the presence of Na-alcoholate, even at 0 °C to give esters [121]. Dienes with isolated double bonds react with carbon monoxide and alcohols at mild reaction conditions in the presence of Pd/HCl to give unsaturated monocarboxylic acid esters and at more severe conditions to give saturated dicarboxylic acid esters [508]. 

Suitable catalysts for ring closure reactions are cobalt carbonyls [123, 280, 673, 674], rhodium carbonyls [280, 678], iron carbonyl [123] and certain palladium compounds [679]. Nickel carbonyls, the active catalysts in the Reppe syntheses, are inactive in most cases [123, 673]. A few examples in which nickel is active are the formation of phenols from allyl halides, acetylene and carbon monoxide, which is only a side reaction, and the mechanistically unclear formation of lactones from allyl carbinol and bu-tyne-l-ol-4 [438]. 

Chen AA, Kaminsky M, Geoffrey GL, Vannice MA. Carbon monoxide hydrogenation over carbon-supported iron-cobalt and potassium-ironicobalt carbonyl cluster-derived catalysts. 

Wilkinson s catalyst is useful for effecting intramolecular decarbonylation of aldehydes to hydrocarbons with retention of configuration (Walborsky and Allen, 1971). Decarbonylation of disubstituted cyclopropenones by iron, nickel, or cobalt carbonyls results in the formation of alkynes (Bird and Hudec, 1959). Tetraphenylethylene was obtained in 68% yield by reaction of diphenylketene with cobalt carbonyl (Hong et ai, 1968). 

Unlike the iron triad complexes, cobalt triad compounds, particularly those of Rh and Ir are much more active in hydrosilation catalysis, although the cobalt carbonyl Co2(CO)g has played a very important role in furthering understanding of the catalytic cycle with transition metals. Recently, a simple cobalt salt, CoBr2, in conjunction with added Bu"P, Znl2 and BU4NBH4 was shown to afford 1,4-hydrosilated isoprene (silicon at C-4) in 90% isolated yield, where most metal catalysts derived from Ru, Rh, Pd and Pt usually lead to a mixture of regioisomers. ... 

A similar dependence of the activity of bimetallic catalysts on their composition is observed in the synthesis of hydrocarbons with increasing content of palladiiun, the activity drops by 1-2 orders of magnitude. Supporting of iron, cobalt, rutheniiim, or rhodium carbonyls on Cu/Si02 also suppressed the activity of these metals for synthesis of hydrocarbons from CO and H2 by 1-2 orders of magnitude. 

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. 

Reduction of unsaturated aldehydes seems more influenced by the catalyst than is that of unsaturated ketones, probably because of the less hindered nature of the aldehydic function. A variety of special catalysts, such as unsupported (96), or supported (SJ) platinum-iron-zinc, plalinum-nickel-iron (47), platinum-cobalt (90), nickel-cobalt-iron (42-44), osmium (<55), rhenium heptoxide (74), or iridium-on-carbon (49), have been developed for selective hydrogenation of the carbonyl group in unsaturated aldehydes. None of these catalysts appears to reduce an a,/3-unsaturated ketonic carbonyl selectively. 

Carbonvlation of Benzyl Halides. Several organometallic reactions involving anionic species in an aqueous-organic two-phase reaction system have been effectively promoted by phase transfer catalysts(34). These include reactions of cobalt and iron complexes. A favorite model reaction is the carbonylation of benzyl halides using the cobalt tetracarbonyl anion catalyst. Numerous examples have appeared in the literature(35) on the preparation of phenylacetic acid using aqueous sodium hydroxide as the base and trialkylammonium salts (Equation 1). These reactions occur at low pressures of carbon monoxide and mild reaction temperatures. Early work on the carbonylation of alkyl halides required the use of sodium amalgam to generate the cobalt tetracarbonyl anion from the cobalt dimer(36). 

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