Theoretical study of the mechanism of CO substitution reaction in the complexes M(η5-Cp)(η1-Cp)(CO)2] (I) , [M(η5-Cp)(η1-indenyl)(CO)2] (II) and [M(η5-indenyl)(η1-indenyl)(CO)2] (III)

In this investigation, density functional theory calculations were used to compare the CO substitutions reaction of the Cp (Cp=C5H5) and indenyl(Indenyl=C7H9) ligands in the complexes (ƞ5-C5H5) Fe (CO)2(ƞ1-C5H5) (I), (ƞ5-C5H5) Fe (CO)2(ƞ1-indenyl) (II), (ƞ5-indenyl) Fe (CO)2(ƞ3-indenyl) (III). The reaction dissociation of carbonyl ligands leads to the formation of sandwich complexes Fe(η5-C5H5)2, Fe (η5-C5H5) (η5-indenyl) and Fe (η5-indenyl)2. The activation energy barrier of CO substitutions reaction was calculated for complexes I, II and III. Our calculations show that he activation energy barrier in the first and second CO substitution reactions in complexes II and III is higher than in complex I which indicate that the pair of π - bonded electron in the ƞ3-indenyl ligand has less Nucleophilic properties than the ƞ3- cyclopentadienyl ligand. In addition, calculations show that the monocarbonyl complexes are stable in the exo form and the CO substitution by endo ƞ3-indenyl form never happens.