Dicobalt octacarbonyl, and

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). 

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 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). 

Cyclohexylamine, which was one of the best promoters for the stoichiometric reaction, failed to give the catalytic version under the pressure of CO (7 atm). However, Krafft and co-workers used cyclohexylamine coupled with dicobalt octacarbonyl and/or even tetracobalt dodecacarbonyl in DME for a catalytic cyclization. Cyclohexylamine is a relatively sterically bulky amine and is presumed to leave the unsaturated dicobalt species intact and to make CO more labile. ... 

The syntheses of many Co3(CO)9X compounds from dicobalt octacarbonyl and XCCI3 have been optimized 347), and further reactions starting from 0(60)4 and XCCI3 360), or RCF —Co(CO)4 46) have been investigated in order to determine the mechanism of formation of the clusters. Methinyltricobalt enneacarbonyls are also formed from Co2(CO)g and such apical carbon precursors as acetylenes 140), dimethyl ketene 408), or carbyne chromium complexes (7 73). In several cases (7 72,... 

The cobalt(O) complex shown in Entry 2 (Table 3.49) could be prepared either by heating a mixture of an alkyne cobalt carbonyl complex with polystyrene-bound tri-phenylphosphine, or by pretreating resin-bound triphenylphosphine with dicobalt octacarbonyl and then treating the resulting support with the alkyne. 

Heck (59) has suggested that the first step in the carboxylation reaction is the formation of cobalt hydrocarbonyl, which can be formed from dicobalt octacarbonyl and solvent (55). Alkylation and carbonylation then produce an acylcobalt carbonyl. Reaction of the acylcobalt carbonyl with the compound containing active hydrogen then regenerates cobalt hydrocarbonyl, e.g.,... 

IV. Properties, Structure, and Preparation of Dicobalt Octacarbonyl and Cobalt... 

Rate Data for Reduction of Benzhydrol to Diphenylmethane Using 0.5 mole benzhydrol, 150 ml. of a benzene solution containing 7.8 g. dicobalt octacarbonyl, and an initial pressure of 3500 p.s.i. of 1 1 synthesis gas (1H2 1C0)... 

The unique hydrogenating ability of a mixture of synthesis gas and a cobalt catalyst is intimately associated with the chemistry of the cobalt compounds formed under these conditions, namely dicobalt octacarbonyl and cobalt hydrocarbonyl. Before any mechanism for the hydrogenation reaction is discussed it is imperative to consider, if even briefly, the chemistry of the cobalt carbonyls. 

Recent work (Wender, Sternberg, and Orchin, 36) suggests a revision of the view (Hieber, Muhlbauer, and Ehmann, 37) that the reaction between dicobalt octacarbonyl and compounds like methanol, ethanol pyridine, and o-phenanthroline involves only the displacement of one or more carbon monoxide groups of the carbonyl by the base according to Equation (1), using pyridine as an example. 

Equation (2) is representative of a group of reactions between dicobalt octacarbonyl and a compound having an available unshared pair of electrons, i.e., a base in the Lewis sense. It is apparent from the above equations that there has been an internal exchange of electrons and... 

The cited evidence supports the hypothesis that a carbonium ion intermediate can be formed under oxo conditions. The subsequent course of reactions leading to the reduced product is more speculative. With benzhydrol, for example, the diphenylmethyl carbonium ion can be formed from dicobalt octacarbonyl and benzhydrol via the following reactions ... 

It was also discovered that the exo-isomer was formed exclusively in the reaction (except in cases involving norbornadiene where the formed exoisomer underwent irreversible isomerisation to the entfo-isomer, catalysed by dicobalt octacarbonyl) and noted when the products are derived from unsymmetrical acetylenes (MeC=CH or PhC=CH) only a single position isomer is isolated... it is readily shown that the single substituent always occurs on the carbon atom adjacent to the carbonyl group , 3... 

Livinghouse and co-workers were successfully able to employ 5mol% dicobalt octacarbonyl and CO at atmospheric pressure by irradiating the reaction mixture with high-intensity visible light.52 Later, they confirmed that it was possible to perform the reaction in the absence of the irradiation,... 

Cool the reactor to —196° and remove the noncondensable materials by pumping. Allow the reactor to warm to 0° and remove the excess trifluorosilane, tetracarbonyl(trifluorosilyl)-cobalt, and any cobalt carbonyl hydride formed by pumping the volatile products through a — 78° (Dry Ice-acetone mixture) trap into a —196° trap. A dark residue will remain in the reactor consisting of unreacted dicobalt octacarbonyl and decomposition products. Unreacted trifluorosilane will be in the —196° trap. 

The species shown in the system 8.13 are those present under reaction conditions. At lower temperatures and pressures, a wealth of different complexes are present, including dicobalt octacarbonyl and cationic complexes of cobalt that differ depending on what cobalt compound was initially charged [17,23-25]. 

Sodium cobalt carbonylate, Na Co(CO)4". Colorless powder insoluble in water. It is prepared from dicobalt octacarbonyl and sodium amalgam in ether solution under nitrogen. If a solution in another solvent is required the ether is evaporated in vacuum and the new solvent is added with exclusion of air. 

A series of organometallic block copolymers PS-Z -PPES[Co2(CO)6l (PPES-poly(4-(phenylethynyl)styrene)) with various block sizes were obtained by the reaction between dicobalt octacarbonyl and PS- -PPES (Scheme 5.8)." The metal-free block copolymers were... 

Caution. Both dicobalt octacarbonyl and carbon monoxide are poisonous and therefore the reaction should be carried out in a well-ventilated hood. 

This sequence is similar to that originally suggested (4), except that equilibrium is not maintained bettveen dicobalt octacarbonyl and olefin on the one hand and complex I and carbon monoxide on the other. 

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

Although there is a striking similarity between the iron complexes, V and VI, and the corresponding cobalt complexes (dicobalt octacarbonyl and IV), there is one important difference the iron complexes are anions, while the cobalt complexes are imcharged. With this in mind, it is possible to explain the course of the hydroxymethylation reaction in a manner analogous to that postulated for the hydroformylation reaction. 

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... 

This reaction has found its way into organic synthesis fi and is attractive because of its generality and selectivity. In Drummond s synthesis of hydroxymethylacylfulvene,3 0 for example, a Pauson-Khand reaction of the allene-alkyne 446 gave a 69% yield of 447. In this case, molybdenum hexacarbonyl was used. In Takano s synthesis of dendrobine, 448 was treated with dicobalt octacarbonyl and then NMO to give an 89%... 

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. 

Acetylenes with one bulky substituent are transformed into symmetrically or unsymmetrically substituted cyclopentadienones by the combined action of dicobalt octacarbonyl and carbon monoxide see, for example, equation 55. ... 

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. 

There is other evidence to support the suggestion that Co2(CO)7 does exist. The formation of cobalt hydrocarbonyl from dicobalt octacarbonyl and hydrogen is strongly inhibited by carbon monoxide (26). This fact again suggests that a coordinately unsaturated carbonyl is an intermediate, and Co2(CO)7 would seem to be the most likely one. 

CoSe2 nanomaterials have also been prepared as catalysts for nitrogen doped carbons as low cost materials. The carbon supports were synthesised by pyrolysis of vulcan, which was coated with carbon and nitrogen precursors with formaldehyde and ethylene diamine or 1,6-diaminohexane being the carbon and nitrogen sources respectively. To load the CoSca layer dicobalt octacarbonyl and nitrogen doped carbon were mixed with 200 ml dehydrated jylene. The carbonyl sol was then refluxed for 2 h at 140 °C in a four neck flask with nitrogen protection. 

Ungvary F (1972) Kinetics and mechanism of the reaction between dicobalt octacarbonyl and hydrogen. J Organomet Chem 36 363... 

Newtcn and Pauson have prepared the 11 -deoxy-PGE precursor (62 R =Me) by forming a complex between the alkyne (98) and dicobalt octacarbonyl and reacting this complex with ethene. The... 

---