Structural and Energetical Characterization of the Methylbutadiene–Fe(CO)3 Isomers and Related Reactive Intermediates with Quantum Chemical Methods

Abstract

A theoretical investigation of isoprene–Fe(CO)3 (2), (E)‐1,3‐pentadiene–Fe(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 functional Becke3LYP, and the results are presented. Special emphasis is placed on cationic, anionic, and radical intermediates formally derived by abstraction of a hydride, a proton, or a hydrogen atom from the methyl group of the parent complexes. The geometry, energy, and electronic situation of the calculated species are discussed in the context of experimental facts. This 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 resonance formulae. The calculation of transition states of isomerization (or racemization) processes even permits a quantitative description of energy profiles. In this way, the configurational stability of relevant cationic, anionic and radical intermediates can be estimated.

Organometallic Radicals: Thermodynamics, Kinetics, and Reaction Mechanisms

“…160 The radical complexes 1 and 2 are formally derived by abstracting a hydrogen atom from the isoprene-Fe (CO) 3 complex (Figure 10.18). 160 The radical complexes 1 and 2 are formally derived by abstracting a hydrogen atom from the isoprene-Fe (CO) 3 complex (Figure 10.18).…”

“…The two pathways are depicted in Figure 10.20. 160 Adapted with permission from Wiley-InterScience. pyramidal product with the acetyl ligand at the basal site. TS2a leads to an acyl product having a square pyramidal geometry in which the acetyl ligand takes the apical position (2a).…”

“…FIGURE 10.19 Structure of the radical complexes 3, 4, and 5 formally derived from abstraction of a hydrogen atom from the neutral pentadiene-Fe(CO) 3 complex and the mesomeric forms of 3, 4, and 5. 160 Adapted with permission from Wiley-InterScience. Spin densities are given in parentheses.…”

Stoichiometric Applications of Acyclic π-Organoiron Complexes to Organic Synthesis

“…Subsequently, Lillya, et al, demonstrated that ionization of the hydroxyl substituent occurs with anchimeric assistance from iron and that isomerization of the initially generated transoid pentadienyl cation (57) to the more stable cisoid cation occurs with retention of configuration about the C1-C2 bond [65]. Recent DFT calculations on the parent cation (R = R 1 = R 4 = R 5 = H) predict that the cisoid structure (56) is 9.2 kcal mol -1 more stable than the transoid structure (57) [66]. Concordant with this energy difference, the NMR spectra of nearly all (pentadienyl)Fe(CO) 3 + cations reveal only the cisoid geometry.…”

Synthesis and Characterization of the Peroxo Complexes of Uranium (VI) Containing Organic Acids and Amine Bases Ligands

“…The synthesis of well defined heteroligand peroxo-metal complexes therefore is an important prerequisite for a heuristic approach in this field of chemistry. It is imperative to note that in recent years a commendable progress has been made in this aspect of lighter metals and a good amount of newer information as well as materials has emerged thereof [13][14][15].…”