Cobalt carbonyls tetracarbonyl hydride

T,he hydroformylation reaction or oxo synthesis has been used on an industrial scale for 30 years, and during this time it has developed into one of the most important homogeneously-catalyzed technical processes (I). A variety of technical processes have been developed to prepare the real catalyst cobalt tetracarbonyl hydride from its inactive precursors, e.g., a cobalt salt or metallic cobalt, to separate the dissolved cobalt carbonyl catalyst from the reaction products (decobaltation) and to recycle it to the oxo reactor. The efficiency of each step is of great economical importance to the total process. Therefore many patents and papers have been published concerning the problem of making the catalyst cycle as simple as possible. Another important problem in the oxo synthesis is the formation of undesired branched isomers. Many efforts have been made to keep the yield of these by-products at a minimum. 

Carbon monoxide has been found to be surprisingly reactive toward the metals in Group VIII, in both their oxidized and unoxidized states. A sizable number of compounds exist in which one or more CO molecules are attached to a metal atom through the carbon typical of these are nickel tetracarbonyl, Ni(CO)4, iron pentacarbonyl, Fe(CO) cobalt carbonyl hydride, Co(CO)4H platinum carbonyl chloride, Pt(CO)2Cl2 and more complicated molecules such as Co4(CO)i2. 

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. 

Detailed mechanisms for the amidocarbonylation reaction have been proposed by both Pino [2] and Magnus [4], wherein the first step is the formation of a hemi-amidal, followed by the nucleophilic substitution of a hydroxyl group by cobalt tetracarbonyl hydride and carbonyl insertion to an (ct-amidoalkanoyl) cobalt intermediate. This intermediate then provides the desired 7V-acyl-a-amino acid by direct hydrolysis, or via an lactame intermediate, followed by hydrolysis. 

This alkoxycarbonylation reaction is also catalytic, if the alkylcobalt tetracarbonyl is formed from an epoxide and cobalt carbonyl anion in a hydroxylic solvent (9). A stoichiometric amount of base is not required in this reaction. The initial product, a derivative of the anion of 2-hydroxy-ethylcobalt tetracarbonyl, may undergo three reactions (a) react with more epoxide to give polymer, (b) undergo an internal hydride shift to form aldehyde or ketone, or (c) undergo protonation, carbon monoxide insertion, and alcoholoysis (or hydrolysis) to form ester (or acid). Varying amounts of... 

Cobalt carbonyl. See Cobalt tetracarbonyl Cobalt carbonyl hydride. See Cobalt hydrocarbonyl... 

Heck has formulated a mechanism which accounts for hydroformylation of olefins catalyzed by cobalt carbonyl (68). A modification of this mechanism is presented in Fig. 5. Cobalt octacarbonyl reacts with hydrogen to form the tetracarbonyl hydride. It is proposed that this coordinatively saturated complex loses a CO group to form the four-coordinate hydride (LX). Coordination of an olefin yields the olefin complex (LXI). Migration of hydride yields an unsaturated alkyl complex (LXII). Further insertion of a CO group (undoubtedly by a migration mechanism) affords the four-coordinate acyl cobalt(I) complex (LXIII). Oxidative addition of hydrogen affords the hypothetical dihydride (LXIV), which eliminates the product aldehyde and regenerates the cobalt(I) hydride catalyst (LX). This latter... 

E. Hydroformylation and related carbonylation reactions Treatment of olefins with carbon monoxide and hydrogen under pressure and in the presence of dicobalt octacarbonyl gives mainly aldehydes or ketones. Alcohols and paraffins are formed as by-products. The hydroformylation of olefins to aldehydes is of considerable industrial importance. The prediction that cobalt tetracarbonyl hydride was a catalyst in these reactions [93, 94] has been amply verified for example the stoicheio-metric hydroformylation of 1-pentene by HCo(CO)4 proceeds at room temperature giving isomeric alddiydes [95]. It has been shown that HCo(CO)4 is formed under the hig pressure (100 atm. 1 1 H2 CO) and temperature (100-300°) conditions used in hydroformylation reactions [95, 96]. 

Methyl acetate probably originates from the reaction of methanol with the intermediate cobalt-acyl complex. The reaction leading to the formation of acetaldehyde is not well understood. In Equation 8, is shown as the reducing agent however, metal carbonyl hydrides are known to react with metal acyl complexes (20-22). For example, Marko et al. has recently reported on the reaction of ri-butyryl- and isobutyrylcobalt tetracarbonyl complexes with HCo(CO) and ( ). They found that at 25 °C rate constants for the reactions with HCo(CO) are about 30 times larger than those with however, they observed that under hydroformylation conditions, reaction with H is the predominant pathway because of the greater concentration of H and the stronger temperature dependence of its rate constant. The same considerations apply in the case of reductive carbonylation. Additionally, we have found that CH C(0)Co(C0) L (L r PBu, ... 

Apart from the work on binary metal carbonyls and metal carbonyl hydrides, Flieber and his school also greatly extended the field of carbonyl(ni-trosyl) metal complexes. The first compound of the general composition M(CO)x(NO)- was obtained by Robert L. Mond and Albert Wallis as early as in 1922 [67]. While studying the reactivity of Co2(CO)8 toward various substrates, they observed that slowly at room temperature, but almost instantaneously at 40°C, nitric oxide gas reacts with cobalt tetracarbonyl to form a cherry-red liquid, with the evolution of carbon monoxide . This liquid was... 

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