Cobalt -, iodide

The catalyst of choice is cobalt iodide with various promotors from Group 15 elements. The process is mn at 140—200°C, 28—41 MPa (4,000—6,000 psi), and gives an 88% conversion with 90% selectively to acetaldehyde. Neither of these acetaldehyde syntheses have been commercialized. 

Grignard reagents add to diketene ia the presence of cobalt iodide [15238-00-3] C0I2, or palladium [440-05-3] to give 3-methylenecarboxyhc acids, used ia terpenoid and hormone syntheses, as well as monomers for radical copolymers (116,117) (see Hormones Terpenoids). 

The relatively minor alteration in reaction conditions can be seen to drastically alter the nature of the product (468). In addition many sulfoxide complexes are thermally degraded, and in consequence the extent of drying can alter the nature of the product. Thus, the complex [Co(0-Me2SO)8][I]2 is isolated from a cobaltous iodide-dimethyl sulfoxide system, but extensive drying in vacuo causes degradation to yield [Co(0-Me2SO)6][CoI4] (128). 

Formula C0I2 MW 312.74 also forms a hexahydrate, Col2 6H20, MW 420.83 Synonyms cobaltous iodide cobalt diiodide... 

Elemental composition Co 18.84%, 1 81.16%. C0I2 may be identified from its varying colors in different solvents. Under varying conditions, its aqueous solution may be analyzed for cobalt by AA, ICP or other instrumental techniques after appropriate dilution (see Cobalt). Iodide anion may be analyzed in sufficiently diluted aqueous phase hy ion chromatography. Also, the analy-... 

In a more detailed examination of the ruthenium-cobalt-iodide "melt" catalyst system, we have followed the generation of acetic acid and its acetate esters as a function of catalyst composition and certain operating parameters, and examined the spectral properties of these reaction products, particularly with regard to the presence of identifiable metal carbonyl species. 

It is clear that ruthenium-cobalt-iodide catalyst dispersed in low-melting tetrabutylphosphonium bromide provides a unique means of selectively converting synthesis gas in one step to acetic acid. Modest changes in catalyst formulation can, however, have profound effects upon liquid product composition. 

The iodide content of the catalyst formulation is the key to avoiding these problems of competing reactions and achieving maximum acetic acid selectivity. The addition of iodide ensures that any initially formed methanol (7) is rapidly (H) converted to the more electrophilic methyl iodide. However, further increases in the quantities of iodide beyond that needed for methanol conversion to methyl iodide may lead to a portion, or all, of the catalytic-ally active cobalt carbonyl reverting to catalytically inactive cobalt iodide species - e.g. the [Col4] anion identified in this work, or possibly the cationic [Co(MeOH) (CO) I species (9). 

The reaction of dimethyl carbonate with synthesis gas requires a cobalt-iodide catalyst and operating conditions of 180 C and 4000 psig. The acetaldehyde rate approaches 30 M/hr with selectivities greater than 85%. The productivities are much better than with methanol however, recycle of the CO and methanol back to dimethyl carbonate is very difficult ... 

It has been reported ( ) that homogeneous ruthenium- or cobalt-iodide-based complexes catalyze the homologation of esters of carboxylic acid to their next higher homologues, for instance ... 

Cobaltous bromide and cobaltous iodide in the solid state absorb ammonia with formation of hexammino-cobaltous bromide, [Co(NH3)6]Br2, and hexammino - cobaltous iodide, [Co(NH3)6]I2, respectively. The compounds are unstable, and rapidly lose ammonia on heating and decompose on solution in water. Tetrammino-cobaltous iodide, [Co(NH3)4]I2, is also known. It may be prepared by treating a concentrated solution of cobaltous iodide with ammonia a pale red precipitate is formed, which gradually dissolves on warming, giving a violet-coloured liquid from which small rose-red crystals of the tetram-mine separate. It also is unstable, and decomposes on heating or on standing in air with loss of ammonia and formation of cobalt oxide. In aqueous solution it turns brown, ammonia is evolved, and a precipitate of cobaltous oxyiodide separates. 

Hexammino-cobaltic Iodide, [Co(NH8)8]I3, is produced by the method described above, using hydrogen iodide. It is a dark orange-coloured body, less soluble in water than the bromide, being almost insoluble in cold water and only sparingly soluble in hot. 

If heated in neutral solution it is completely decomposed. Aquo-pentammino-cobaltic bromide, [Co(NH3)5H20]Br3, and aquo-pent-ammino-cobaltic iodide, [Co(NH3)5H20]I3, are prepared by similar means. 

The anionic nickel acetylacetonate catalyst gives only the cis, cis, trans product. Intermediate catalysts have already been seen to give cis, cis, cis structures which do not terminate but produce cis polybutadiene. This will also be seen later with cobalt iodide. At high temperatures or with strongly cationic systems the cyclic dodecatrienes are isomerized to the most stable trans, trans, trans structure. 

The most important synthetic processes are (1) the oxidation of acetaldehyde, and (2) the direct synthesis ftom methyl alcohol and carbon monoxide. The latter reaction must proceed under very high pressure (approximately 650 atmospheres) and at about 250 C. The reaction takes place 111 the liquid phase and dissolved cobaltous iodide... 

The thermochemical aspects of these reactions have been discussed in terms of heats of formation of the halides of elements of the iron group, and of the acceptor metal (75). The yield of carbonyls was especially favored with the iodides and also with sulfides or sulfur-containing materials (76). With iron and cobalt iodides the reaction is facilitated by formation of the carbonyl iodide as an intermediate. 

The basic steps of the catalytic cycle with the cobalt catalyst are shown in Fig. 4.3. The tetracarbonyl cobalt anion 4.7 is formed from cobalt iodide, by reactions 4.5-4.7. 

Cobalt iodide is most readily obtained in solution by warming the finely divided metal with water and iodine. Its formation is accompanied by evolution of heat. It may also be obtained by allowing cobalt to remain in prolonged contact with water and iodine.2... 

A cobalt/iodide catalyzed process to make acetic acid from methanol, introduced by BASF around 1960, grew out of the carbonylation studies by... 

The BASF cobalt/iodide catalyzed process for methanol carbonylation was quite quickly superseded by a rhodium/iodide catalyzed process discovered at Monsanto and first commercialized in 1970 at a plant in Texas City. The Monsanto process was a significant advance and became one of the few large tonnage processes to use a homogeneous transition metal catalyst. It was later... 

The ability of bis(7/ -allyl)cobalt iodide to catalyze the polymerization of butadiene without addition of any further reagent was discovered by Wilke et al. [17], Mainly cw-1,4-polybutadiene was obtained as well as some 1,2 units. In combination with AlBr3 the activity increases considerably and almost pure cA-1,4-polybutadiene is formed. Unfortunately, no further details are reported. However, it seems plausible to conclude that the cationic bis( -butenyl)cobalt(III) fragment, which can react with butadiene by tj -cis coordination, should be considered as the real catalyst of the 1,4-cA polymerization. 

A particularly broad potential for application in syngas reactions is shown by ruthenium carbonyl clusters. Iodide promoters seem to favor ethylene glycol (155,156) the formation of [HRu3(CO),]- and [Ru(CO)3I3]- was observed under the catalytic conditions. These species possibly have a synergistic effect on the catalytic process. Imidazole promoters have been found to increase the catalytic activity for both methanol and ethylene glycol formation (158-160). Quaternary phosphonium salt melts have been used as solvents in these cases the anion [HRu3(CO)u] was detected in the mixture (169). Cobalt iodide as cocatalyst in molten [PBu4]Br directs the catalytic synthesis toward acetic add (163). With... 

Derivation Heating cobalt powder with hydriodic acid anhydrous cobaltous iodide is prepared by heating cobalt in iodine vapor. 

Pyrazolin-5-ones react with salts of various metals to form compounds in which the pyrazolinone has reacted in its enolic form with replacement of the enolic hydrogen to give a salt and having semipolar bonds formed by donation of electrons to the metal by the nitrogen atoms393 394 Usually these compounds contain the number of pyrazolinone residues corresponding to the valence of the metal atom. Such salts as cuprous iodide, ferric iodide, cobaltous iodide, silver iodide and silver diiodide participate in such reactions.393,394 In addition, complexes may be formed in which there has been no elimination of a small molecule between the reactants and no formation of ionic bonds.432... 

The reactivity of the catalyst is enhanced by azeotropic drying of the cobalt complex before use, thus allowing the reaction of sterically hindered and silyl-substituted alkynes. Good reactivity between norbornadiene and disubstituted alkynes (yields in homo-Diels-Alder adducts ca. 85%) is also achieved by adding zinc powder to cobalt iodide/triphenylphosphane catalysts. " ... 

The production of acetic acid by carbonylation of methanol (Equation (1)) can also be traced back to the 1950s when Reppe and coworkers at BASF developed a cobalt iodide catalyst that was effective for this reaction at relatively high temperatures and pressures 250 °C, 600 bar) [1,2]. 

This process operates in the aqueous phase at 250 C and 65.10 Pa absolute, in the presence of cobalt iodide as catalyst The high-pressure reactor lined with hastelloy C for corrosion resistance features internal agitation of the liquid obtained by gas injection ( air lift type). It is continuously supplied with a stream of methanol, dimethyl ether, carbon monoxide if required, and water preheated to between 40 and 80°C. The amount of water added is one-third of that of methanol by weight The arid mixture and the unreacted gases are collected at the top of the reaction tower, cooled, and brought to 1.10 Pa absolute in a flash drum. The methyl iodide and header components in, the Hashed gases are recovered by scrubbing with methanol feed. ... 

The liquid effluent from the flash drum is first degassed. The vapors consisting of methyl iodide and formate, acetaldehyde and methyl acetate, are dissolved in the azeotrope produced by the subsequent acetic add dehydration column. The degassed arid mixture is then distilled to remove the light components and the cobalt iodide, which is recycled to the reactor in the form of an aqueous slurry. This mixture is then dehydrated and purified by azeotropic distillation. The third compound employed is one of the reaction products (methyl acetate, bp10l3 = 70.4°C, water content 8.5 per cent weight). The column has about 60 trays.. ... 

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