Theoretical study of the CO dissociation mechanism in [(ƞ 5 -C 5 H 5 ) Fe (CO) 2 (ƞ 1 -C 5 H 5 )]

in this study, using theoretical calculations of DFT density functions, CO substitution reactions in cyclopentadiene and indenyl ligands in complexes [(ƞ 5 - C5H5) Fe (CO)2(ƞ 1 -C5H5)] (I) Which leads to the formation of sandwich complex Fe(η 5 -C5H5)2 were investigated. The free energy barrier of CO dissociation process for complex I was calculated. The first CO substitution giving an η 2 -Cp complex has a higher barrier than the second CO substitution giving an η 5 -Cp complex. This behavior was attributed to the increased degree of aromaticity of Cp in the transition state connecting the η 2 -Cp complex to the η 5 -Cp complex. Calculations show that first and second CO substitution reactions different take place through the formation of two monochromonyl Endo and Exo isomeric. Finally, it was found that the pathway is more accessible to the CO substitution reaction through the Exo-isomer intermediate.