Carbon monoxide reaction with dicobalt

An organometallic equivalent that opens epoxides is a hydrosilane, for example, MeaSiH, and carbon monoxide, catalyzed by dicobalt octacarbonyl See 10-55 for other coupling reactions with organosilanes. Silyl enol ethers react with epoxides in a related reaction, but a Lewis acid, such as TiCl4, is required. ... 

Cobalt has an odd number of electrons, and does not form a simple carbonyl in oxidation state 0. However, carbonyls of formulae Co2(CO)g, Co4(CO)i2 and CoJCO),6 are known reduction of these by an alkali metal dissolved in liquid ammonia (p. 126) gives the ion [Co(CO)4] ". Both Co2(CO)g and [Co(CO)4]" are important as catalysts for organic syntheses. In the so-called oxo reaction, where an alkene reacts with carbon monoxide and hydrogen, under pressure, to give an aldehyde, dicobalt octacarbonyl is used as catalyst ... 

Carbon Monoxide Process. This process involves the insertion of carbon monoxide [630-08-0] into a chloroacetate. According to the hterature (34) in the first step ethyl chloroacetate [105-39-5] reacts with carbon monoxide in ethanol [64-17-5] in the presence of dicobalt octacarbonyl [15226-74-1], Co2(CO)g, at typical temperature of 100°C under a pressure of 1800 kPa (18 bars) and at pH 5.7. Upon completion of the reaction the sodium chloride formed is separated along with the catalyst. The ethanol, as well as the low boiling point components, is distilled and the nonconverted ethyl chloroacetate recovered through distillation in a further column. The cmde diethyl malonate obtained is further purified by redistillation. This process also apphes for dimethyl malonate and diisopropyl malonate. 

Other processes described in the Hterature for the production of malonates but which have not gained industrial importance are the reaction of ketene [463-51-4] with carbon monoxide in the presence of alkyl nitrite and a palladium salt as a catalyst (35) and the reaction of dichioromethane [75-09-2] with carbon monoxide in the presence of an alcohol, dicobalt octacarbonyl, and an imida2ole (36). 

A somewhat related process, the cobalt-mediated synthesis of symmetrical benzo-phenones from aryl iodides and dicobalt octacarbonyl, is shown in Scheme 6.49 [100]. Here, dicobalt octacarbonyl is used as a combined Ar-I bond activator and carbon monoxide source. Employing acetonitrile as solvent, a variety of aryl iodides with different steric and electronic properties underwent the carbonylative coupling in excellent yields. Remarkably, in several cases, microwave irradiation for just 6 s was sufficient to achieve full conversion An inert atmosphere, a base or other additives were all unnecessary. No conversion occurred in the absence of heating, regardless of the reaction time. However, equally high yields could be achieved by heating the reaction mixture in an oil bath for 2 min. 

Cyclopentanecarboxaldehyde has been prepared by the procedure described above 2 3 by the reaction of aqueous nitric acid and mercuric nitrate with cyclohexene 6 by the action of magnesium bromide etherate 6 or thoria 7 on cyclohexene oxide by the dehydration of frarei-l, 2-cyclohexanediol over alumina mixed with glass helices 8 by the dehydration of divinyl glycol over alumina followed by reduction 9 by the reaction of cyclopentene with a solution of [HFe(CO)4] under a carbon monoxide atmosphere 10 and by the reaction of cyclopentadiene with dicobalt octacarbonyl under a hydrogen and carbon monoxide atmosphere.11... 

Metal Hydrides. Metal hydrides generally react readily with acetylenes, often by an insertion mechanism. Cobalt hydrocarbonyl gives complicated mixtures of compounds with acetylenes. The only products which have been identified so far are dicobalt hexacarbonyl acetylene complexes (34). Greenfield reports that, under conditions of the hydroformy lation reaction, acetylenes give only small yields of saturated monoaldehydes (30), probably formed by first hydrogenating the acetylene and then reacting with the olefin. Other workers have identified a variety of products from acetylene, carbon monoxide, and an alcohol with a cobalt catalyst, probably cobalt hydrocarbonyl. The major products observed were succinate esters (74,19) and succinate half ester acetals (19). 

The reaction of dicobalt octacarbonyl with molecular hydrogen Eq. (17), can occur at room temperature and is similarly inhibited by carbon monoxide, again suggesting an unsaturated intermediate (158). Pino et al. (116) suggested that dicobalt octacarbonyl is in equilibrium with a more reactive lower carbonyl. Natta et al. have also shown that Co4(CO)12 and Co2(CO)8, in the absence of hydrogen, coexist at carbon monoxide pressures corresponding to the highest rates of hydroformylation (104, 158). 

One of the most interesting catalytic reactions to be discovered is the so-called oxo reaction. The oxo reaction consists of the catalytic addition of carbon monoxide and hydrogen to olefins to form, primarily, aldehydes possessing one carbon atom more than the original olefin. This hy-droformylation reaction was developed during World War II by Roelen and co-workers (22) in Germany. While they utilized solid Fischer-Tropsch cobalt-thoria catalyst, it became apparent to them that the hydroformylation reaction was probably a homogeneous catalytic process with either dicobalt octaearbonyl or cobalt hydrocarbonyl as the catalyst. 

Diaryl ditellurium reacted with carbon monoxide at elevated pressures in acetonitrile in the presence of dicobalt octacarbonyl at 125° to give the diaryl tellurium and the Je-aryl tellurolobenzoate12. Formally, these reactions can be considered to be a replacement of one tellurium atom in the diaryl ditellurium by carbon monoxide. Didodecyl ditellurium produced only didodecyl tellurium and no 7e-dodecyl tellurolotridecanoate12. 

H2 — 4H+ + 4(e), and as soon as formed, Co° metal reacts with carbon monoxide to form more dicobalt octacarbonyl which repeats the cycle. The protons are fixed by the pyridine in the form of the pyridinium salt of the hydrocarbonyl. The overall reaction may be represented as follows ... 

The salt is insoluble in water and in solvents such as hexane or toluene and may, therefore, be separated from dicobalt octacarbonyl which is readily soluble in hydrocarbon solvents. Thus, two analyses and the requisite simple calculations permit the estimation of both [Co(CO)4]2 and Co(CO)4-. A convenient apparatus for the determination has been described (Orchin and Wender, 41). Alternately, the concentration of dicobalt octacarbonyl may be measured by adding pyridine to the solution containing the carbonyls. All the dimer is converted to the anion with the evolution of carbon monoxide according to Equation (2). After gas evolution has ceased, a solution of iodine in pyridine may be added. This reagent is similar to aqueous iodine and liberates all the carbon monoxide in the anion originally present as well as that formed from the dimer by reaction with pyridine. 

A 2.0-g. sample of powdered dicobalt octacarbonyl is placed in a 25-ml. glass reactor in a nitrogen-filled glove bag. The reactor is evacuated then 5 g. of trichlorosilane is condensed from the vacuum system into the reactor which has been cooled to —196°. The Teflon stopcock is closed, the reaction vessel allowed to warm to room temperature, and then the reactants are permitted to stand for 24 hours. Cool the reactor to —42° (diethyl ketone slush), open the Teflon stopcock, and remove the excess silane and noncondensable substances into the vacuum system with pumping. The remaining dry, solid material is then transferred in a nitrogen (or carbon monoxide) filled glove bag to a sublimation apparatus. The solid is then sublimed in vacuo... 

This review has already indicated numerous applications of dicobalt-alkyne complexes in organic synthesis. Like the Nicholas reaction (see Section II,D), the Pauson-Khand reaction has seen widespread use.175 This reaction is a three-component cycloaddition of alkynes with alkenes and carbon monoxide which occurs in the presence of octacarbonyldicobalt to afford cyclopentenones, as shown in Eq. (16). 

When 3-deoxy-l,2 5,6-di-0-isopropylidene-a-D-erythro-hex-3-en-ose (63) was allowed to react with carbon monoxide and hydrogen in the presence of preformed dicobalt octacarbonyl, the reaction... 

A particularly useful synthesis of cyclopentanones involves the coupling of an alkene, an alkyne and carbon monoxide in the presence of dicobalt octacarbonyl (equation 17). The reaction proceeds via an al-kyne-cobalt complex (7) and with relatively unreactive alkenes such as cyclopentene it is preferable to synthesize the complex in a separate step. With highly strained alkenes such as norbomadiene, how-... 

Dicobalt octacarbonyl has been prepared by the thermal decomposition of cobalt tetracarbonyl hydride1 and by the reaction of suspensions of cobalt(II) compounds such as the carbonate in inert organic liquids with carbon monoxide under superatmospheric pressure.2,3 The procedure described here may be regarded as a modification of the second approach. It is superior to the first in giving a higher yield. 

The 0X0 reaction, which involves heating an olefin with hydrogen and carbon monoxide under pressure in the presence of dicobalt octacarbonyl, with the introduction of a formyl or (hydroxymethyl) group at one carbon atom, is believed to proceed by the addition of the hydride HCo(CO)4 across the double bond, followed by insertion of CO into the newly formed carbon-cobalt bond. It would be anticipated that the cobalt ion would be nucleophilic and would therefore mainly attack glycals at C-1. In accordance with this view, the products of the reaction with the model glycal 2,3-dihydro-4Ff-pyran have been found to contain 78% of 2-(hy-... 

The fact that the rate varies inversely with carbon monoxide pressure has led to the postulation (4, 5) that the first step involves the reaction of the olefin with dicobalt octacarbonyl to form an olefin-carbonyl complex, I, and carbon monoxide. Martin (6) showed that the following sequence of equations led to a kinetic expression which fits the data obtained with different ratios of gases at elevated pressures quite well ... 

There is good reason for believing that the reaction of I with carbon monoxide [Equation (3)] yields dicobalt octacarbonyl and the thermody-... 

Item 4 is the basis for the postulate that the first step involves formation of an olefin-carbonyl complex and carbon monoxide by reaction of dicobalt octacarbonyl with the olefin ... 

Decomposition of the complex by reaction with hydrogen or cobalt hydrocarbonyl, HCo(CO)4, which also may be present, is then suggested to yield tile aldehyde and a precursor of dicobalt octacarbonyl. Dicobalt octacarbonyl is formed again by reaction of this precursor with carbon monoxide. 

An interesting cyclization reaction was reported that involved the reaction of dienes, diynes, or ene-ynes with transition metals to form cyclopentenone derivatives in the presence of carbon monoxide.363 in a simple example, ene-yne 444 was heated with dicobalt octacarbonyl and CO to give a 68% yield of 445.364 jjjj transformation has become an important synthetic tool known as the Pauson-Khand reaction.365 jhe mechanism probably involves insertion of the alkene (or alkyne) into the transition metal bond, which is why it is presented in this section. Formally, it is a [2+2+l]-cycloaddition, but the accepted mechanism is the one proposed by Magnus,364 and shown in Figure 13.8.366 n has been stated that further study is required to... 

Two general methods have been used for the preparation of cyclopentadienylcobalt dicarbonyl the reaction between dicobalt octacarbonyl and cyclopentadiene and the reaction of bis (cyclopentadienyl) cobalt with carbon monoxide at elevated temperatures and pressures. The method given here is a modification of the second method, and as in the preparation of cyclopentadienylvanadium tetracarbonyl described above, avoids isolation of the intermediate pyrophoric bis(cyclopentadienyl)metal derivative. 

AstraZeneca published the use of an immobilized transition metal carbonyl complex as a catalyst in the Pauson-Khand reaction [67]. This reaction is known to produce useful products but it also suffers from a number of drawbacks dicobalt octacarbonyl and its analogs are volatile, toxic, and unstable due to loss of carbon monoxide and aerial oxidation. These drawbacks can be avoided by the use of an immobilized metal carbonyl complex (Scheme 13), which is safe and convenient to handle (see also [68]). It offers the additional advantages of being reusable after recovery from the reaction medium and the product becomes less contaminated with metal carbonyl remnants. The reaction was applicable to a wide range of substrates with the exception of tetra-substituted alkenes. A typical reaction of enine 32 to the bicyclic enone 33 is depicted in Scheme 13. 

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