Octacarbonyl dicobalt

It is used to produce carbonyl iron (finely divided iron) for high frequency coils and also for radio and television (Merck 1996). It is also used as a catalyst in many organic syntheses and as an antiknock agent in motor fuels. 

Colorless oily liquid that turns yellow stable but sensitive to air and light freezes at -20°C (-4°F) boils at 103 C (217 F) density 1.50 at 20°C (68°F) vapor density 6.74 (air = 1) insoluble in water, slightly soluble in alcohol, and readily dissolves in most organic solvents. 

Iron pentacarbonyl is highly toxic, the acute toxicity, however, is lower than that of nickel tetracarbonyl. The toxic symptoms, however, are nearly the same. Being highly volatile [the vapor pressure being 30 torr at 20° C (68°F)], this compound presents a serious risk of inhalation to its vapors. Furthermore, it evolves toxic carbon monoxide when exposed to light. The reaction is as follows  

Therefore, all handling and operations must be carried out in fume hoods or under adequate ventilation. Inhalation of its vapor can 

Highly flammable liquid flash point (closed up) — 15°C (5°F) vapor pressure 40 torr at 30.3 C (86 F) (CRC Handbook 1996) autoignition temperature 50°C (122°F). It ignites in air. It reacts violently with strong oxidants including ozone and hydrogen peroxide. Explosion has been reported when heated rapidly with nitric oxide above 50° C (122°F) in an autoclave (Bretherick 1995). Reactions with other oxides of nitrogen under similar conditions are expected to be explosive. 

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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 ... 

The cobalt catalyst can be introduced into the reactor in any convenient form, such as the hydrocarbon-soluble cobalt naphthenate [61789-51 -3] as it is converted in the reaction to dicobalt octacarbonyl [15226-74-17, Co2(CO)g, the precursor to cobalt hydrocarbonyl [16842-03-8] HCo(CO)4, the active catalyst species. Some of the methods used to recover cobalt values for reuse are (11) conversion to an inorganic salt soluble ia water conversion to an organic salt soluble ia water or an organic solvent treatment with aqueous acid or alkah to recover part or all of the HCo(CO)4 ia the aqueous phase and conversion to metallic cobalt by thermal or chemical means. 

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). 

Unmodified Cobalt Process. Typical sources of the soluble cobalt catalyst include cobalt alkanoates, cobalt soaps, and cobalt hydroxide [1307-86 ] (see Cobalt compounds). These are converted in situ into the active catalyst, HCo(CO)4, which is in equihbrium with dicobalt octacarbonyl... 

Dicobalt octacarbonyl [10210-68-1] M 341.9, m 51 . Orange-brown crystals by recrystn from n-hexane under a carbon monoxide atmosphere [Ojima et al. J Am Chem Soc 109 7714 1987 see also Hileman in Preparative Inorganic Reactions, Jolly Ed. Vol 1 101 1987]. 

In addition to rhodium(III) oxide, cobalt(II) acetylacetonate or dicobalt octacarbonyl has been used by the submitters as catalyst precursors for the hydroformylation of cyclohexene. The results are given in Table I. 

Arylmetallic compounds have various, but not very widely used, applications in organic synthesis. Examples are acyl-de-metallation reactions using either dicobalt octacarbonyl in tetrahydrofuran (Seyferth and Spohn, 1969 Scheme 10-92), or carbon monoxide and a rhodium catalyst (Larock and Hershberger, 1980). 

Seyferth, D., Spohn, R. J., Churchill, M. R., Gold, K. Scholer, F, R. (1970) Co8(CO)24C6, a bis(tricobaltnonacarbonyl)/dico-balt hexacarbonyl derivative of 2,4-hexadiyne from the reaction of dicobalt octacarbonyl with hexachlorocyclopropane, J. Or-ganomet. Chem. 23, 237-255. 

MeaSiH) and carbon monoxide, catalyzed by dicobalt octacarbonyl See 10-92... 

Symmetrical ketones can be prepared in good yields by the reaction of organo-mercuric halides with dicobalt octacarbonyl in THF, or with nickel carbonyl in DMF or certain other solvents. The R group may be aryl or alkyl. However, when R is alkyl, rearrangements may intervene in the C02(CO)g reaction, though the Ni(CO)4 reaction seems to be free from such rearrangements. Divinylic ketones... 

When dicobalt octacarbonyl, [Co(CO)4]2, is the catalyst, the species that actually adds to the double bond is tricarbonylhydrocobalt, HCo(CO)3. Carbonylation, RCo(CO)3- -CO—>RCo(CO)4, takes place, followed by a rearrangement and a reduction of the C—Co bond, similar to steps 4 and 5 of the nickel carbonyl mechanism shown in 15-30. The reducing agent in the reduction step is tetra-carbonylhydrocobalt HCo(CO)4, ° or, under some conditions, H2. When HCo(CO)4 was the agent used to hydroformylate styrene, the observation of CIDNP indicated that the mechanism is different, and involves free radicals. Alcohols can be obtained by allowing the reduction to continue after all the carbon monoxide is... 

By analogy with hydroformylation, dicobalt octacarbonyl has been examined as a hydrosilylation catalyst. Various silanes and a-olefins react, often exothermically. Thermal deactivation occurs above 60° C hence, large exotherms and high temperatures must be avoided (56, 57,130). Isomerization is more pronounced than for the bridged olefin complexes of Pt(II) and Rh(I) (see below) it even occurs with trialkoxysilanes (57). Though isomerization is faster than hydrosilylation, little variation in the relative rates of these two processes with the nature of the silane is observed this is in marked contrast to the bridged systems (55). 

When dicobalt octacarbonyl is added to the silane prior to olefin addition, the activity of the system is drastically reduced 13, 14). 

Jacobsen (1999) has carried out carbomethoxylation of asymmetric epoxides. Thus, the carbomethoxylation of (R)-propylene oxide with CO and methanol yields 92% of (3R)-hydroxybutanoic acid in greater than 99% ee. Similarly, the reaction of (/ )-epichlorohydrin gives 96% of 4-chloro-(3R)-hydroxybutanoic acid in greater than 99% ee. The catalyst consists of dicobalt octacarbonyl and 3-hydroxy pyridine. A continuous process for making enantiomeric 1-chloro-2-propanol has been suggested. With a suitable catalyst propylene reacts with O2, water, cupric and lithium chloride to give 78% of (S)-l-chloro-2-propanol in 94% ee. 

The reaction of dicobalt octacarbonyl with [NP(OPh) (OCgH P-Pl O 3)n gives three different phosphine bound cobalt carbonyls. The initial hydroformylation activity of the heterogeneous catalyst... 

A combination of Co-mediated amino-carbonylation and a Pauson-Khand reaction was described by Pericas and colleagues [286], with the formation of five new bonds in a single operation. Reaction of l-chloro-2-phenylacetylene 6/4-34 and dicobalt octacarbonyl gave the two cobalt complexes 6/4-36 and 6/4-37 via 6/4-35, which were treated with an amine 6/4-38. The final products of this domino process are azadi- and azatriquinanes 6/4-40 with 6/4-39 as an intermediate, which can also be isolated and separately transformed into 6/4-40 (Scheme 6/4.11). 

A typical example of this is the dicobalt octacarbonyl catalyzed hydroformylation of olefins to yield aldehydes. According to the classical mechanism proposed by Heck and Breslow /29/ (Equations 28-31), the cobalt carbonyl reacts with hydrogen to form hydrido cobalt tetracarbonyl, which is in equilibrium with the coordinatively unsaturated HCo(C0)2. The tricarbonyl coordinates the olefin, and rearranges to form the alkyl cobalt carbonyl. 

The hypothesis that the cobalt carbonyl radicals are the carriers of catalytic activity was disproved by a high pressure photochemistry experiment /32/, in which the Co(CO), radical was prepared under hydroformylation conditions by photolysis of dicobalt octacarbonyl in hydrocarbon solvents. The catalytic reaction was not enhanced by the irradiation, as would be expected if the radicals were the active catalyst. On the contrary, the Co(C0)4 radicals were found to inhibit the hydroformylation. They initiate the decomposition of the real active catalyst, HCo(C0)4, in a radical chain process /32, 33/. 

The synthesis of phthalimidines by dicobalt octacarbonyl-catalyzed carbonylation of Schiff bases was first described by Pritchard78 and the scope of the reaction was evaluated by Murahashi et a/.79 Later Rosenthal et al.80-83 subjected a variety of related compounds to carbonylation, and also achieved a phthalimidine synthesis directly from benzonitrile under the conditions of the oxo process.84 An example illustrating the formation of a phthalimidine is shown in Scheme 49 a comprehensive review of the scope and mechanism of reactions of this type is available.85... 

The dicobalt octacarbonyl-catalyzed transformation of azoarenes into 2-arylindazolin-3-ones by carbonylation has been known for many years157 high pressures of carbon monoxide are required and under more forcing conditions the products are quinazoline-2,4-diones (Scheme 92). Reactions... 

The indazoline products can also be made directly from the palladium complexes 78 by heating them with the isonitrile in toluene at 120CC.162 They are also formed in dicobalt octacarbonyl-catalyzed reactions of azo-arenes with isocyanides but in this case an alternative reaction pathway leading to indazolo[2,l- ]indazoles (79) is observed (Scheme 96).163 Products of the latter type are formed from sterically hindered isocyanides hence it is likely that in these cases a double metallation is favored over isocyanide insertion into a monometallated species (Scheme 97). 

A direct synthesis of triarylimidazoles and triarylimidazolines has been accomplished by the dicobalt octacarbonyl-catalyzed reaction of benzyla-mine derivatives with carbon tetrachloride. When the reaction temperature is 150°C a complex product is formed and yields of heterocyclic products are poor. By lowering the reaction temperature to 120°C or reducing the reaction time, or by using [Mo(CO)6] and [f)5-C5H5Mo(CO)3]2 as the... 

Subtle differences in the behavior of azoarenes toward cobalt carbonyl derivatives are observed in regard to metal-complex formation. Azobenzene is transformed by dicobalt octacarbonyl in processes of orthometallation and carbonyl insertion into 2-phenylindazolin-3-one (see Section IV,D,2). In contrast, cyclopentadienylcobalt dicarbonyl effects N—N bond cleavage, and carbonylation of the isolable complex 88a provides 1 -phenylbenzimid-azolin-2-one (Scheme 106).171... 

Pyrrolidone is the major product when allylamine is subjected to the conditions of the oxo process using dicobalt octacarbonyl as the catalyst.203 The by-products are pyridine derivatives 112 and 113 and these compounds become the major products when iron pentacarbonyl is used as the catalyst ... 

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. 

The [2+2+1] cycloaddition of an alkene, an alkyne, and carbon monoxide is known as the Pauson-Khand reaction and is often the method of choice for the preparation of complex cyclopentenones [155]. Groth and coworkers have demonstrated that Pauson-Khand reactions can be carried out very efficiently under microwave heating conditions (Scheme 6.75 a) [156]. Taking advantage of sealed-vessel technology, 20 mol% of dicobalt octacarbonyl was found to be sufficient to drive all of the studied Pauson-Khand reactions to completion, without the need for additional carbon monoxide. The carefully optimized reaction conditions utilized 1.2 equivalents of... 

The binary metal carbonyls are named by giving the name of the metal followed by the name carbonyl, with the number of carbonyl groups indicated by the appropriate prefix. For example, Ni(CO)4 is nickel tetracarbonyl, whereas Cr(CO)6 is chromium hexacarbonyl. If more than one metal atom is present, the number is indicated by a prefix. Thus, Co2(CO)8 is dicobalt octacarbonyl, and Fe2(CO)9 has the name diiron nonacarbonyl. 

Dicobalt octacarbonyl and bis(triphenylphosphine)carbonyl chloroiri-dium catalyzed analogous hydrogen-deuterium exchanges (28). 

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... 

Cobalamin, 25 803 folic acid and, 25 802 Cobalt (Co), 7 207-228. See also Co-base superalloys 60Co isotope 60Co nucleus Fe-Ni-Co alloys Dicobalt octacarbonyl Tetracobalt dodecacarbonyl analysis, 7 215-216 in ceramic-matrix composites, 5 554t coke formation on, 5 266 colloidal suspensions, 7 275 economic aspects, 7 214-215 effect on copper resistivity, 7 676t environmental concerns, 7 216 health and safety factors, 7 216-218 in M-type ferrites, 11 66, 69 occurrence, 7 208... 

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