Cobalt 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. 

Co(C04)H Cobalt tetracarbonyl hydride, 2 238, 240 Co(CO)4K Cobalt tetracarbonyl hydride, potassium salt, 2 238 [Co(C204),JK3 Potassium trioxa-latocobaltate(III), 1 37 [Co(Ci,H14N202)]2H20 Bis-(N, N -disalicylalethylenedi-amine-g-aquodicobalt(II), 3 196, 198, 200... 

The optical antipodes of tris(l,10-phenanthroline)nickel-(II) perchlorate are more stable than those of the corresponding tris(2,2 -bipyridine)[tris(2,2 -dipyridyl)] compound. In 18 hours, solutions of the 1,10-phenanthroline complexes lose only 50% of their activity. When examined at 589.0 and 546.1 m/x, the antipodes show a large abnormal rotatory dispersion. The precipitation of [Ni(o-phen)s]-[Co(CO)4]2 is the basis for a method of determining cobalt tetracarbonyl hydride. ... 

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. 

Hvdrofonnybtion is a homogeneous catalysis reaction which employs a coordination complex of cobelt with the olefin. The catalyst precursor is a cobalt salt which is converted tn siru, in the presence of CO and H , to cobalt tetracarbonyl hydride in equilibrium with cobalt tricarbonyl hydride. The latter, which displays a vacant coordination position, forms a complex with the olefm. The olefin undergoes chemical conversions leading to the production of two isomeric aldehydes, and the normal aldehyde is favored in relation to the iso-compound in the ratio of 4/1. 

Table 9.8 gives economic data about Oxo synthesis on propylene for processes using cobalt tetracarbonyl hydride phosphine-modified cobalt and phosphine-modified rhodium catalysts. 

Caution. Some cobalt tetracarbonyl hydride results in this reaction. Because of its toxicity, previously outlined precautions1 must be observed. 

Cobalt tetracarbonyl hydride is prepared by the reaction of acids with salts containing the cobalt tetracarbonyl anion, [Co(CO)4]-.1-6 Alkali metal salts, obtained by treating alkaline cobalt(II) cyanide suspensions with carbon monoxide,1,4,6,7 can be employed,1-3 but either the hexapyridinecobalt(II) salt or the pyridinium salt gives higher yields.5... 

Certain of the properties of cobalt tetracarbonyl hydride have been summarized previously.4 The pure compound decomposes thermally by a second-order process5 to hydrogen and dicobalt octacarbonyl. The compound is strongly... 

Co(CO)4K Cobalt tetracarbonyl hydride, potassium salt, 2 238 [Co(CO)4]2 Dicobalt octacarbonyl, 2 238, 242 6 190, 194 [Co(CO)4]2[Co(C6H5N)6] Cobalt tetracarbonyl hydride, hexa-pyridinecobalt(II) salt, 5 192 [Co(CO)4]2[Ni(C,2H8N2)3] Cobalt tetracarbonyl hydride, tris-(1,10-phenanthroline)nickel-(II) salt, 5 193n., 195 [Co (C204) 3JK3 Potassium trioxa-latocobaltate(III), 1 37 [Co(C5H5N)a][Co(CO)4]2 Cobalt tetracarbonyl hydride, hexa-pyridinecobalt(II) salt, 5 192 Co(C5H702)3 Cobalt(III) acetyl-acetonate, 6 188... 

The alkali salt of cobalt tetracarbonyl hydride can best be prepared by the absorption of carbon monoxide in an alkaline cobalt(II) cyanide suspension. Treatment of this solution with nitric oxide yields the volatile cobalt nitrosyl tricarbonyl/ while treatment with acid yields the volatile cobalt tetracarbonyl hydride. At room temperature, the latter compound decomposes into hydrogen and the nonvolatile dicobalt octacarbonyl, [Co(CX))4]2. 

The shaker containing the yellow solution of the potassium salt of cobalt tetracarbonyl hydride is connected with the nitric oxide reservoir (ssmthesis 37), swept with nitric oxide, and the shaking action started. Soon the solution turns red, and after a time a yellow vapor appears above the solution. From this point on, the solution is swept slowly with nitric oxide at the rate of 2 l./hour for 5 hours, with the... 

The product thus obtained in the trap is reasonably pure. Any trace of cobalt tetracarbonyl hydride is eliminated by allowing the trap to stand at room temperature for 24 hours. The trap is then cooled again to about —79° and the system connected to a prepared sample tube. After the system has been evacuated, the trap is allowed to warm up. Cooling the sample tube causes the cobalt nitrosyl tricarbonyl to distill into the latter. Finally, the capillary of the sample tube is sealed in the flame. Yield 2.5 g. (58 pe cent). 

The procedure for the preparation of the potassium salt of cobalt tetracarbonyl hydride is carried out as already described. Because acidification of this solution liberates not only the hydride but also 700 ml. of carbon dioxide, the operation cannot be carried out in the shaker owing to excessive foaming. 

The cobalt tetracarbonyl hydride that is frozen out in the trap is white to light yellow. It melts at —33° to a light-... 

Cobalt tetracarbonyl hydride cannot be preserved at room temperature except at pressures that would burst the usual glass sample tube. However, small quantities of the material as a yellow vapor will remain in equilibrium with hydrogen and the solid dicobalt octacarbonyl. 

It is noteworthy that cobalt tetracarbonyl hydride vapor mixed with large amounts of carbon monoxide at room temperature can be carried through long connections and a drying train without obvious sign of decomposition. 

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