Reactions of Cobalt Carbonyls

Cobalt carbonyl radicals and radical reactions of cobalt carbonyl. G. Palyi, F. Ungvary, V. Galamb andL. Marko, Coord. Chem. Rev., 1984, 53, 37-53 (90). 

Literature examples on the reaction of cobalt carbonyl(49), cobalt carbonyl anion( ), and iron carbonyl anion( ) with propylene oxide have been reported. However either the reaction conditions required are severe, the yields are low, or the reaction is not catalytic. 

Based on the known reactions of cobalt carbonyls, the catalytic cycle shown in Fig. 4.7 has been suggested. The hydrido carbonyl 4.11 is converted to 4.19, a formyl species. Formyl complexes are considered to play a key role in all... 

Reactions of cobalt carbonyl with nonaromatic thiones differ significantly from the aforementioned conversions. 5-Alkyl xanthates, for example, react by the rupture of C—R and C=S bonds to afford alkoxy alkylidyne tricobalt nonacarbonyl clusters, [RO—CCosfCO),] (41) (vide infra). On the other hand, dithioesters, R C(S)SR, react with [CojfCO) ] to give alkylidyne tricobalt nonacarbonyl clusters in yields between 49 and 74%. The R groups include methyl, isopropyl, and phenyl (42). 

Both Co2(CO)g and Co4(CO),2 are oxidized by air even in the solid state, and by halogens. With the latter, complete decomposition to CO and Co(II) halides occurs. Reaction of cobalt carbonyl derivatives with I2 in pyridine is frequently used for analyses by gas volumetry of CO evolved. Octacarbonyldicobalt, Co2(CO)g, is attacked by organic substances that contain active protons and converted to the corresponding Co(II) salts , as in reactions for Fe(CO)j [equations (1) and (m), 14.6.2.3.2]. Included here is reaction of Co2(CO)g with cyclopentadiene to give dicarbonylcyclopentadienylcobalt(I) as a dark red oil (b.p. 75 C/22 torr) ... 

By analogy with the bonding of olefins, it might have been expected that for acetylenes, where there are two n bonds at right angles to each other, a metal atom could be bound to each. This possibility has been realized, for example, in the reaction of cobalt carbonyl with acetylenes of various types ... 

Co2(CO)8 and HCo(CO)4 using HP-IR. A cobalt carbonyl-butadiene complex and an allylcobalt carbonyl species were formed from the reaction of butadiene with Co2(CO)8. Reaction with HCo(CO)4 gradually afforded an alkenyl complex which reacted to form further byproducts. The reaction of cobalt carbonyls with hydrogen or deuterium, and the stoichiometric interaction of the resultant hydride with alkenes has also been studied with HP-IR. Ojima reported HP-IR studies into Co-Rh bimetallic carbonyl catalysts, and observed a CoRh(CO)7 species which was active for hydroformylation-amidocarbonylation. 

Some analogs of methinyltricobalt enneacarbonyl systems with silicon, germanium, and tin in place of the methinyl carbon atom have been studied. The reaction product of C02(CO)q with tetraphenylsilane was once erroneously believed (228) to be [SiCo3(CO)9]2, but it was later (316) proved that the material was 010003(00)9, formed by reaction of cobalt carbonyl... 

Coordinatively Unsaturated Cobalt Carbonyls Relevant to Hydro-formylation. The negative effect of carbon monoxide partial pressure on the rate of hydroformylation was the first indication of the participation of coordinatively unsaturated cobalt carbonyls in the catalysis of aldehyde formation and of the accompanying olefin isomerization. The retarding effect of carbon monoxide has also been observed in cobalt-catalyzed olefin and aldehyde hydrogenation and in various other reactions of cobalt carbonyls as well. It was assumed that in these reactions in fast reversible carbon monoxide dissociation highly reactive coordinatively unsaturated complexes are formed in very low concentrations, undetectable by conventional analytical methods. By using sophisticated new methods, in some cases the detection and characterization of these elusive species has become possible. 

Based on high pressure infrared spectra, the presence of Co(CO)4 radicals in solutions of Co2(CO)8 in n-hexane has been confirmed in the temperature range of 120-210°C (233). For more information about cobalt carbonyl radicals and radical reactions of cobalt carbonyls, see Ref (234). 

The participation of the 17-electron Co(CO)4 radical in various reactions of cobalt carbonyls has been deduced from the observation that the rate of these reactions was found to be proportional to the square root of the Co2(CO)8 concentration (139-141,143,145,151,238-240). This can be related to the fast equilibrium formation of 00(00)4 from 0o2(00)s, which is then involved in the... 

Ma.nufa.cture. Nickel carbonyl can be prepared by the direct combination of carbon monoxide and metallic nickel (77). The presence of sulfur, the surface area, and the surface activity of the nickel affect the formation of nickel carbonyl (78). The thermodynamics of formation and reaction are documented (79). Two commercial processes are used for large-scale production (80). An atmospheric method, whereby carbon monoxide is passed over nickel sulfide and freshly reduced nickel metal, is used in the United Kingdom to produce pure nickel carbonyl (81). The second method, used in Canada, involves high pressure CO in the formation of iron and nickel carbonyls the two are separated by distillation (81). Very high pressure CO is required for the formation of cobalt carbonyl and a method has been described where the mixed carbonyls are scmbbed with ammonia or an amine and the cobalt is extracted as the ammine carbonyl (82). A discontinued commercial process in the United States involved the reaction of carbon monoxide with nickel sulfate solution. 

Organomercury compounds undergo a similar reaction. Alkyl and aryl Grignard reagents can be converted to carboxylic esters with Fe(CO)5 instead of CO. Amides have been prepared by the treatment of trialkyl or triarylboranes with CO and an imine, in the presence of catalytic amounts of cobalt carbonyl ... 

Treatment of the 1,2-oxazines 52 with carbon monoxide at 1000 psi in the presence of cobalt carbonyl brings about insertion of carbon monoxide to form the 1,3-oxazepines S3 <96TL2713>. A convenient route to P-lactams fused to oxepines is made available by alkene metathesis. Thus reaction of 4-acetoxyazetidin-2-one with ally alcohol in the presence of zinc acetate, followed by iV-allylation of the nitrogen affords the derivative 54 which cyclises by RCM to form the oxazepinone 55 <96CC2231>. The same communication describes a similar synthesis of 1,3-dioxepines. 

These sites must be considered to have different catalytic properties. The sites on top (Co atoms of low coordination) would be similar to that of the central atom of cobalt carbonyl complexes, and reactions on these should be similar to those in hydroformylation. Specifically, insertion reactions between n- and cr-ligands (CO... 

Stoichiometric, nucleophilic addition of alkylcobalt compounds to carbonyl compounds were reviewed in 1996.374 This chapter focuses on recent progress in the reactions of cobalt enolates with carbonyls and cobalt-catalyzed coupling reactions. 

A method for observing intermediates directly in the reaction cycle is in situ IR spectroscopy under reaction conditions. As early as 1975, Penninger published a contribution concerning in situ IR spectroscopic studies of cobalt carbonyl modified by tri-u-butylphosphine as a hydroformylation catalyst [58] at relatively low catalyst concentrations of 2 mmoll-1. The observed carbonyl... 

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). 

The reaction conditions were mild (room temperature, 1 atm CO) and a two-fold excess of base was used along with a catalytic amount of cobalt carbonyl. The product distribution was quantified by VPC. The mixtures contained starting material, ester product, and various amounts of methyl benzyl ether. No detectable amounts of benzyl alcohol, ketones, or hydrocarbons were seen. Potassium methoxide alone afforded mostly the ether. A mixture of potassium methoxide and alumina gave a slight improvement in ester yield but the predominant product was again the ether. In contrast, when potassium methoxide on alumina was used, the carboxyalkylated product, methyl phenylacetate, was prepared in 70 yield with little ether detected. Benzyl chloride reacted in a similar fashion under these mild reaction conditions. Other alkoxide and carbonate bases could be used as... 

Cyclododecene may be prepared from 1,5,9-cyclododecatriene by the catalytic reduction with Raney nickel and hydrogen diluted with nitrogen, with nickel sulfide on alumina, with cobalt, iron, or nickel in the presence of thiophene, with palladium on charcoal, with palladimn chloride in the presence of water, with palladium on barium sulfate, with cobalt acetate in the presence of cobalt carbonyl, and with cobalt carbonyl and tri- -butyl phosphine. It may also be obtained from the triene by reduction with lithium and ethylamine, by disproportionation, - by epoxidation followed by isomerization to a ketone and WoliT-Kishner reduction, and from cyclododecanone by the reaction of its hydrazone with sodium hydride. ... 

Metal derivatives of cobalt carbonyl hydride such as Tl[Co(CO)4], Zn[Co(CO)4]2, or Cd[Co(CO)4]2 are formed upon reaction of cobalt octacarbonyl with these metals in the presence of carbon monoxide under pressure. Reaction with halogens (X) produces cobalt carbonyl halides, Co(CO)X2. 

Chung provided one of the simple solutions based on this line of concept. Under the high pressure of carbon monoxide, the higher homolog of cobalt carbonyls including Co4(CO)i2 is depressed, and the considerable amount of Co2(CO)8 becomes available. This is now used for the catalytic reaction at high temperature of 150 °C. 

The Schiff bases from substituted benzaldehydes and anilines will carbonylate in the presence of cobalt carbonyl, as catalyst at 225°C. producing phthalimidine derivatives, XVI, in good yield (70, 52). This reaction may be explained as an... 

Fig. 4. Stability of cobalt carbonyl catalyst [Co2(CO)8 and HCo(CO)4] as a function of CO partial pressure and reaction temperature (57, 58). (Reproduced with permission of Ernest Benn Ltd. and Springer-Verlag.)...

Step 4 Decobaltation of the Reaction Product. The product of the hydroformylation reactor containing the catalyst as a mixture of cobalt carbonyl hydride and dicobalt octacarbonyl is fed to the decobaiting section. Mixing the product at 120 °C and 10 atm with a dilute formic acid/ cobalt formate solution in the presence of air decomposes the catalyst (Reaction 9) (12). 

---