Iron, carbon formation mechanism

Using the analogy of model reactions of alkane oxidation in mixtures ofFe(II) and dioxygen in solvents, a mechanism invoking the formation of intermediate with an iron-carbon bond followed by interaction with soxygen was proposed (Waller and Fimscomb, 1996 Shilov, 1997). 

The vinylcyclopropanes (87) interact with Fe(CO)5 to give the complexes (mechanism involving complex formation at the vinyl double bond followed by opening of the cyclopropane ring to give a 7r-allylic intermediate with an iron-carbon a bond has been mentioned (513). 

We propose mechanisms for carbon formation in the presence of hydrogen on nickel and iron surfaces. Benzene is assumed to adsorb on the metal surface and to be hydrogenated to intermediates. These intermediates decompose to form atomic carbon which migrates through a metal crystallite to form carbon filaments. 

It follows from the existence of conformational scissors (Fig. 4) that in the polymerization of symmetric or quasisymmetric dienes in hydrocarbon media on an active center with a slightly polar carbon-metal bond the primary acts of monomer attachment lead to the cis-conformation of the end unit. This conclusion is in good agreement with the modern concepts of the formation mechanism of the cis-structure of anionic polydienes [70]. According to these concepts this is followed by either the attachment of the next monomer molecule or by the cis-trans isomerization of the end unit. The microstructure is fixed at the moment of the attachment of a new monomer unit to the active center, the configuration (cis- or irons-) of the end unit being retained in the polymer chain ... 

We modeled the sequence of transformations of adsorbed reactants on the NiS-FeS surface [138]. The thermodynamics of each step of this mechanism was calculated. Figure 21.1 shows the AGr values for each step of the proposed mechanism of carbon fixation pathway obtained at the B3LYP/TZVP level of theory. In the first step carbon monoxide was added into the Fe-Ni-S model by binding with the iron center (formation of the Fe-CO center). This step is characterized by positive AGr value equal to 4.3 kcal/mol. This shows that the above reaction will most likely not proceed in a gas phase at 373 K temperature. 

Met] Metauer, G., Schissle, J.-M., Study of Mechanism of Martensite Formation in Certain Iron-Carbon-Silicon and Iron-Carbon-Nickel Alloys (in French), Mem. Scient Rev. Metall, 71(5), 295-306 (1974) (Experimental, Crys. Stmcture, Morphology, 13)... 

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