Carbon monoxide, substitution kinetics

The kinetics and mechanism for oxygen transfer between 4-cyano-V,V,-dimethylaniline V-oxide and a C2-capped mexo-tetraphenylporphyrinatoiron(III) and mc5 o-tetrakis(pentafiuorophenyl)-porphyrinatoiron(III) have been established. Addition of a copper(II) porphyrin cap to an iron(II)-porphyrin complex has the expected effect of reducing both the affinities and rate constants for addition of dioxygen or carbon monoxide. These systems were studied for tetradecyl-substituted derivatives solubilized by surfactants such as poly(ethylene oxide) octaphenyl ether. ... 

Acyliron complexes with central chirality at the metal are obtained by substitution of a carbon monoxide with a phosphine ligand. Kinetic resolution of the racemic acyliron complex can be achieved by aldol reaction with (1 R)-( I (-camphor (Scheme 1.14) [41], Along with the enantiopure (R, c)-acyliron complex, the (Spe)-acyliron-camphor adduct is formed, which on treatment with base (NaH or NaOMe) is converted to the initial (SFe)-acyliron complex. Enantiopure acyliron complexes represent excellent chiral auxiliaries, which by reaction of the acyliron enolates with electrophiles provide high asymmetric inductions due to the proximity of the chiral metal center. Finally, demetallation releases the enantiopure organic products. 

Substitution reactions may be carried out thermally, photochemically, and chemically. In a thermal substitution, heat is used to both increase the kinetics of the process and shift the equilibrium, especially when gaseous carbon monoxide is produced, the A S of the reaction being normally positive. 

Cu(II) to yield a paramagnetic Cu(II)-thiolate complex/ Carbon dioxide coordinated to Ni(0) may be reduced to CO by R—SH (R = H, alkyl, benzyl, phenyll, or substituted phenyl) providing a model for carbon monoxide dehydrogenase enzyme. The disulfide generated in this reaction reacts further with the Ni(0) complex to give Ni(SR)2/ The kinetics of the reduction of Cr(VI) by l-methionine (represented by RSCH3) provides the rate law (45), with values for /c2... 

When D2O was substituted for H2O no deuterium was found in the unreacted methane analysed mass spectrometrically at 10% conversion of methane to carbon monoxide. No H-D exchange with hydrogens of methane has been observed in the CH4 -h H2O -h D2 system. In the case of nickel catalyst supported on y-alumina F containing 7.0% Ni) the kinetic dependences (log rate versus log Pch4 nd log Ph2o) e different. Some incorporation of deuterium into methane was found when the CH4 -h D2O reaction was carried out at 10 torr of CH4. The rate of the reaction Wfor low methane pressures (at constant hydrogen pressure) has been found to be... 

The nickel compounds NiRa(bipy) react with a variety of alkenes, including ethylene, norbomadiene, maleic anhydride, and tetracyanoethylene, to produce Ni(bipy)(alkene) or Ni(bipy)(alkene)2. A kinetic study, supported by characterization of intermediates from the reactions with aorolein and with acrylonitrile, indicates that the reaction mechanism involves the intermediacy of transient complexes NiR2(bipyXalkene), containing the alkene TT-bonded to the nickel as in the products. There is a correlation between the rates of these reactions and the stabilities of the respective complexes Ni(bipy)(alkene). The unstable species CoH(LL)2, where LL = bipy or phen, undergo substitution reactions with, for example, carbon monoxide, in which one LL ligand is replaced. One LL can also be replaced by alkyl halides here the reaction is oxidative elimination rather than simple substitution. ... 

Hueso, J. L. Martinez-Martinez, D. Caballero, A. et al. Near-ambient X-ray photoemission spectroscopy and kinetic approach to the mechanism of carbon monoxide oxidation over lanthanum substituted cobaltites. Catal. Commun. 2009, 10, 1898-1902. 

The complex rm f-[Fe(LLH)2(py)a], with LL = diphenylgjyoximate, reacts with carbon monoxide in chlorobenzene solution. The determined rate law, the positive activation entropy, and the variation of the rate constant where the py ligands are replaced by their p-methyl or m-chloro-derivatives, are all consistent with a limiting 5n1 D) mechanism for these reactions as for those of the [Fe(CN)6L] complexes discussed in the previous paragraph. Preparative and equilibrium studies have been made of the complex [Fe(tim)(NCMe)2] +, where tim is the quadridentate macrocyclic ligand (36) derived from 1,3-diaminopropane and 2,3-butanedione. These studies suggest that kinetic studies of reactions of this complex could provide information on novel substitution reactions of iron(n), for example the (reversible) replacement of the acetonitrile ligand by carbon monoxide. ... 

---