Bimolecular reaction cobalt

The formation of II has been postulated above to explain the dissociation of hydrogen by the catalyst. There is independent evidence for the existence of a complex such as II. It has been shown that cobalt hydrocarbonyl, HCo(CO)4, reacts with olefins at room temperature (in the absence of synthesis gas) to form aldehydes 10). Since cobalt hydrocarbonyl is the source of both hydrogen and carbon monoxide in this reaction, at least two molecules of hydrocarbonyl must react with one of olefin. Either a termolecular reaction between two molecules of hydrocarbonyl and one of olefin or two consecutive bimolecular reactions must occur [Equation... 

Nevertheless, cobaltous ions form efficient redox initiating systems with peroxydisulfate ions. " Tertiary aromatic amines also participate in bimolecular reaction with organic peroxides. One of the unpaired electrons on the nitrogen atom transfers to the peroxide link, inducing decomposition. No nitrogen, however, is found in the polymer. It is therefore not a true redox type initiation and the amine acts more like a promoter of the decomposition. Two mechanisms were proposed to explain this reaction. The first one was offered by Homer et al... 

For isopropanol p " 1010 exp(-124//J7) l/(mol s) (the conditions are the same). Naturally, in nonaqueous solutions oxidation occurs more slowly. For example, cobalt acetylacetonate in a chlorobenzene solution oxidizes alcohols via the bimolecular reactions with the following constants (393 K, E. Denisov, V. Solyanikov, V. Martem yanov, 1966) ... 

The reaction does not feature a bimolecular step, such as direct Sn2 attack of the hydroxide nucleophile on the cobalt center. Rather, hydroxide ion participates in a prior-equilibrium reaction, and the actual rate-controlling reaction is believed to be the uni-molecular expulsion of the leaving group from a species that contains a coordinated... 

Recently proof has been reported for a heterometallic bimolecular formation of aldehyde from a manganese hydride and acylrhodium species [2], Phosphine free, rhodium carbonyl species show the same kinetics as the cobalt system, i.e. the hydrogenolysis of the acyl-metal bond is rate-determining. Addition of hydridomanganese pentacarbonyl led to an increase of the rate of the hydroformylation reaction. The second termination reaction that takes place according to the kinetics under the reaction conditions (10-60 bar, 25 °C) is reaction (3). The direct reaction with H2 takes place as well, but it is slower on a molar basis than the manganese hydride reaction. 

Similar considerations apply to the role of spin equilibria in electron transfer reactions. For many years spin state restrictions were invoked to account for the slow electron exchange between diamagnetic, low-spin cobalt(III) and paramagnetic, high-spin cobalt(II) complexes. This explanation is now clearly incorrect. The rates of spin state interconversions are too rapid to be competitive with bimolecular encounters, except at the limit of diffusion-controlled reactions with molar concentrations of reagents. In other words, a spin equilibrium with a... 

The polymer matrix isolates the metal sites, preventing undesirable side-reactions, such as the formation of bimolecular metal-based adducts. UV-Vis and EPR measurements showed that the cobalt centers in the polymer matrix form 1 1 NO-cobalt adducts on exposure to NO gas, but are relatively inert towards O2, CO and CO2. The uptake of NO by this sensing polymer caused an immediate colour change of the initial orange material to the brown-green cobalt-NO adducts. The formation of this sensor- on function occurred at room temperature. However, the release of NO was found to be slow at room temperature in a NO free environment (80% release in 30 days). Under vacuum at 120 °C, the regeneration of the starting material was achieved within 1 h. 

Two major mechanisms have to be taken into consideration for the alkylation of Co -corrins. The classical mechanism of a bimolecular nucleophilic substitution reaction at carbon (the Co -corrin acts as a nucleophile) leads to /3-aUcylated Co -corrins with high diastereoselectivity. Secondly, an electron transfer-induced radical process (where the Co -corrin acts as a one-electron reducing agent) may also lead to cobalt alkylation. The observed formation of incomplete a-aUcylated Co -corrins under kinetically controlled conditions has been proposed to occur via this path. The high nucleophilic reactivity of Co -corrins and their diastereoselective nucleophilic reaction on the ( upper ) /3-face are not increased by the nucleotide function on the ( lower ) a-face rather they appear to be an inherent reactivity of the corrin-bound tetracoordinate Co -center. Among the organometallic B12 derivatives prepared to date, neopentylcobalamin, benzylcobalamin, and... 

The unprotonated forms react by a bimolecular step with rate constant 1.7 x 10 M s at 25 °C in 40% MeOH-HgO. Reaction of the acid form is imimolecular with a rate constant 1.6 x 10 s involving two-electron oxidation of the metal from cobalt(i) to cobalt(m). This requires a rapid reaction between cobalt(i) and cobalt(iii) to give the cobalt(ii) product. Methylcobalamin is also involved in methane biosynthesis. ... 

The stability constants for the coordination of pyridine or substituted pyridines to various alkylcobalt porphyrin systems have been reported. This study has been done in order to observe the m-influence of hydroporphyrin macrocycles on axial position and alkyl exchange reactions. The alkyl exchange reactions of organocobalt(lll) porphyrins with a cobalt(ll) complex of a distinguishable porphyrin or tetrapyrrolc have been studied. The equilibrium constants for the alkyl transfer have been reported. The exchange of the axial ligand is reversible and it follows a bimolecular mechanism. Thermodynamic and activation parameters for homolytic Co-C bond dissociation have been obtained on the (TAP)CoC(CH3)2CN complex (TAP = tetraanisylporphirinato). ... 

Of four possible processes considered it was suggested that the reactions proceed either by a concerted transfer of a carbanion from cobalt to chromium accompanied by electron transfer from chromium to cobalt or alternatively by an Sb2 mechanism involving bimolecular homolytic substitution at saturated... 

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