Structural and energetical characterization of the methylbutadiene-Fe(CO)(3) isomers and related reactive intermediates with quantum chemical methods

A theoretical investigation of isoprene-Fe(CO)(3) (2), (E)-1,3-pentadiene-F e(CO)(3) (3), (Z)-1,3-pentadiene-Fe(CO)(3) (4), and reactive intermediates derived from these complexes was undertaken, employing the HF/DFT hybrid fu nctional Becke3LYP, and the results are presented. Special emphasis is plac ed on cationic, anionic, and radical intermediates formally derived by abst raction of a hydride, a proton, or a hydrogen atom from the methyl group of the parent complexes. The geometry, energy, and electronic situation of th e calculated species are discussed in the context of experimental facts. Th is leads to a better mechanistic understanding of the chemistry of acyclic butadiene-Fe(CO)(3) complexes, provides insights into structural details of the intermediates involved, and allows the evaluation of possible resonanc e formulae. The calculation of transition states of isomerization (or racem ization) processes even permits a quantitative description of energy profil es. In this way, the configurational stability of relevant cationic, anioni c and radical intermediates can be estimated.