Cobalt reaction with methanol

In the Dynamit Nobel/Hercules process no solvent is used. A mixture of cobalt and manganese ethyl hexanoate is used as the catalyst under relatively mild conditions, about 160°C and 7 atm pressure. The product under these conditions is toluic acid, which is isolated and then converted into the methyl ester. The important point to note is that under the operating conditions toluic acid does not undergo any further oxidation. This means that toluic acid is more difficult to oxidize than p-xylene. The methyl ester of toluic acid is then co-oxidized with p-xylene. The product obtained is monomethyl terephthalate, which by reaction with methanol is then converted to dimethyl terephthalate. 

Oxidative addition of methyl iodide to the coordinalively unsaturated cobalt (I) species (1) gives the methyl complex (2) which undergoes CO insertion, probably via methyl migration. Elimination of iodine from the acetyl complex (3) and oxidative addition of hydrogen gives (5). Reductive elimination of the primary product acetaldehyde leads to the unsaturaied complex (6) which oxidatively adds iodine. The catalytic cycle is closed by the elimination of hydrogen iodide from (7), which is consumed by reaction with methanol to give methyl iodide. 

Ethanol can also be obtained by the reaction of methanol with synthesis gas at 185°C and under pressure (6.9—20.7 MPa or 68—204 atm) in the presence of a cobalt octacarbonyl catalyst (177). However, although ethanol was the primary product, methyl formate, methyl, propyl and butyl acetates, propyl and butyl alcohols, and methane were all present in the product. 

A Belgian patent (178) claims improved ethanol selectivity of over 62%, starting with methanol and synthesis gas and using a cobalt catalyst with a hahde promoter and a tertiary phosphine. At 195°C, and initial carbon monoxide pressure of 7.1 MPa (70 atm) and hydrogen pressure of 7.1 MPa, methanol conversions of 30% were indicated, but the selectivity for acetic acid and methyl acetate, usehil by-products from this reaction, was only 7%. Ruthenium and osmium catalysts (179,180) have also been employed for this reaction. The addition of a bicycHc trialkyl phosphine is claimed to increase methanol conversion from 24% to 89% (181). 

PET methanolysis involves the reaction of PET with methanol at high temperatures and pressures in the presence of transesterification catalysts such as magnesium acetate, cobalt acetate, and lead dioxide. 

By studying the NMR spectra of the products, Jensen and co-workers were able to establish that the alkylation of (the presumed) [Co (DMG)2py] in methanol by cyclohexene oxide and by various substituted cyclohexyl bromides and tosylates occurred primarily with inversion of configuration at carbon i.e., by an 8 2 mechanism. A small amount of a second isomer, which must have been formed by another minor pathway, was observed in one case (95). Both the alkylation of [Co (DMG)2py] by asymmetric epoxides 129, 142) and the reduction of epoxides to alcohols by cobalt cyanide complexes 105, 103) show preferential formation of one isomer. In addition, the ratio of ketone to alcohol obtained in the reaction of epoxides with [Co(CN)5H] increases with pH and this has been ascribed to differing reactions with the hydride (reduction to alcohol) and Co(I) (isomerization to ketone) 103) (see also Section VII,C). 

Only a few other cobalt complexes of the type covered in this review (and therefore excluding, for example, the cobalt carbonyls) have been reported to act as catalysts for homogeneous hydrogenation. The complex Co(DMG)2 will catalyze the hydrogenation of benzil (PhCOCOPh) to benzoin (PhCHOHCOPh). When this reaction is carried out in the presence of quinine, the product shows optical activity. The degree of optical purity varies with the nature of the solvent and reaches a maximum of 61.5% in benzene. It was concluded that asymmetric synthesis occurred via the formation of an organocobalt complex in which quinine was coordinated in the trans position (133). Both Co(DMG)2 and cobalamin-cobalt(II) in methanol will catalyze the following reductive methylations ... 

The Co2(CO)g/pyridine system can catalyze carbomethoxylation of butadiene to methyl 3-pentenoate (Eq. 6.44) [80]. The reaction mechanism of the cobalt-catalyzed carbalkoxylation of olefins was investigated and the formation of a methoxycar-bonylcobalt species, MeOC(0)Co from a cobalt carbonyl complex with methanol as an intermediate is claimed [81, 82]. 

Synthesis of Tetrakis(polyethyleneoxy)phthalocyanine cobalt (II) (9). The polyethylene-tethered phthalonitrile (0.827 g, 1.0 mmol), 1,5-diazabicyclo [4.3.0] non-5-ene (0.062 g, 0.50 mmol) and cobalt acetate (0.044 g, 0.25 mmol) were added to a reaction vial equipped with a magnetic stir bar. The reaction was then heated to 175°C for 2 hours before reducing the temperature to 95°C and adding toluene. The reaction mixture was then poured into methanol, filtered, and the sohd washed further with methanol. The collected product was then dried under vacuum to yield... 

The results from our work on the reaction of propylene oxide with cobalt carbonyl and base in methanol are given in Table VIII. Several base/metal oxide combinations were evaluated under mild reaction conditions. The difference in activity between the bases was not as pronounced as that observed in the reaction with benzyl halides with the exception of potassium methoxide which, when used alone, gave exclusively the hydroxy ether resulting from methoxide addition to the epoxide ring. However, the activity of sodium... 

One final interesting isomerization achieved in the cobalt carbonyl system should be mentioned. Heck and Breslow (22b) found that acylcobalt tetracarbonyl compounds undergo alcoholysis with the formation of HCo(CO)4. With methanol, the reaction proceeds at 50° ... 

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, ... 

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 ... 

The metal carboxylate insertion mechanism has also been demonstrated in the dicobaltoctacarbonyl-catalyzed carbomethoxylation of butadiene to methyl 3-pentenoate.66,72 The reaction of independently synthesized cobalt-carboxylate complex (19) with butadiene (Scheme 8) produced ii3-cobalt complex (20) via the insertion reaction. Reaction of (20) with cobalt hydride gives the product. The pyridine-CO catalyst promotes the reaction of methanol with dicobalt octacarbonyl to give (19) and HCo(CO)4. 

Reaction of cw- 1,4-Poly butadiene and PVC. Et2AlClt-Cobalt Compound Catalyst. Commercial cw-1,4-polybutadiene prepared with a Et AlCl-cobalt compound catalyst system was freed of antioxidant by solution in benzene and precipitation with methanol. The cis-1,4,polybutadiene had an intrinsic viscosity in benzene at 25 °C of 2.4 and a greater than 96% cis-1,4 content. 

In earlier chapters we noted that metal ions could either activate or deactivate an imine with respect to addition of a nucleophile. We will now see an example of metal-ion activation in action. In fact, the complexes that are formed from 6.39 arise as a result of metal-initiated nucleophilic attack at the imine groups. The reaction of the free ligand 6.39 with methanolic cobalt(n) acetate results in the attack of methanol upon one of the imine bonds of the initially formed complex (Fig. 6-39). 

Metallization. Bident ate formazans that are insoluble in water can be warmed with cobalt, nickel, and copper salts (preferably acetates) to form metal chelates in solvents such as methanol, ethanol, acetone, and dimethylformamide. Metal complexes of tri- and tetradentate formazans are much more stable. Metallization with divalent salts occurs rapidly at room temperature. On reaction with diazo-tized 2-aminophenols or 2-aminonaphthols, coupling and metallization with divalent metal salts can take place concurrently under the same conditions. When coupling is complete, the dye is usually fully metallized. 

In general, alkylation of a cobalt(I)-containing complex, prepared by NaBH4 reduction of the cobalt(III) complex, can be carried out in methanol.7 However, when a powerfully electrophilic alkylating agent is used, both alkylation of the periphery of the macrocycle and reaction with the solvent methanol can prevent formation of any cobalt alkylation product. In these cases dimethylformamide can be used in place of methanol for the alkylation reaction. 

The linear CO stretching frequency for the carbonylated platinum colloid while lower than that found for surface bound CO, is in the range reported for the platinum carbonyl clusters [Pt 3 (CO) 6 ] n / sind we find that the carbonylated colloid is easily transformed into the molecular cluster [Pt 12 (CO) 24 ] (10) reaction with water. The cluster was isolated in 50 yield based on platinum content of the precipitate by extraction with tetraethylammonium bromide in methanol from the aluminum hydroxide precipitated when water is added to the aluminoxane solution. The isolation of the platinum carbonyl cluster reveals nothing about the size or structure of the colloidal platinum particles, but merely emphasizes the high reactivity of metals in this highly dispersed state. The cluster isolated is presumably more a reflection of the stability of the [Pt3(CO)6]n family of clusters than a clue to the nuclearity of the colloidal metal particles - in a similar series of experiments with colloidal cobalt with a mean particle size of 20A carbonylation results in the direct formation of Co2(CO)8. 

Ignition on contact with furfuryl alcohol powdered metals (e.g., magnesium iron) wood. Violent reaction with aluminum isopropoxide -f- heavy metal salts charcoal coal dimethylphenylphosphine hydrogen selenide lithium tetrahydroaluminate metals (e.g., potassium, sodium, lithium) metal oxides (e.g., cobalt oxide, iron oxide, lead oxide, lead hydroxide, manganese oxide, mercur oxide, nickel oxide) metal salts (e.g., calcium permanganate) methanol + phosphoric acid 4-methyl-2,4,6-triazatricyclo [5.2.2.0 ] undeca-8-ene-3,5-dione + potassium hydroxide a-phenylselenoketones phosphorus phosphorus (V) oxide tin(II) chloride unsaturated organic compounds. 

Reaction with an amine, AIBN, CO and a tetraalkyltin catalyst also leads to an amide.Benzylic and allylic halides were converted to carboxylic acids electroca-talytically, with CO and a cobalt imine complex. Vinylic halides were similarly converted with CO and nickel cyanide, under phase-transfer conditions.Allylic (9-phosphates were converted to allylic amides with CO and ClTi=NTMS, in the presence of a palladium catalyst. Terminal alkynes were converted to the alkynyl ester using CO, PdBr2, CuBr2 in methanol and sodium bicarbonate. ... 

In commercial practice, all PET is made using an antimony compound for the final polycondensation stage. The transesterification reaction between DMT and the glycol is catalysed by salts of manganese, zinc, calcium, cobalt, or other metals. At the end of the ester-interchange stage, when essentially all of the methanol has been evolved, the transesterification catalyst is converted to a catalytically inactive and substantially colourless form by reaction with a phosphorus compound such as triphenyl phosphate or phosphite. Polyesters of 1,4-cyclo-hexanedimethanol and DMT or TA are made using complex titanium catalysts. 

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