Theoretical Studies on the Reaction Mechanism of Metal-Assisted CH Activation

D. Balcells, O. Eisenstein

    Research output: Chapter in BookChapterResearchpeer-review

    10 Citations (Scopus)

    Abstract

    CH activation is a key reaction in the functionalization of hydrocarbons. Considerable experimental work has been done to understand, optimize, and use this reaction in stoichiometric and catalytic processes. This chapter is devoted to the description of the computational studies of CH activation occurring in the presence of a transition-metal complex, with a strong focus on mechanistic issues. The chapter starts with the description of mechanisms with early d0 transition-metal complexes, where σ-bond metathesis is prevalent. It then discusses the addition of CH bonds across polar bonds (1,2 addition), which is a variant of σ-bond metathesis. This is followed by a presentation of the oxidative addition mechanism by more electron rich d4-d10 metal centers. CH activation can also occur through other reaction pathways, which are described as nonclassical mechanisms. This includes the σ-complex assisted metathesis mechanism and the use of electron density analysis for mechanism characterization. Calculations have also been found to be reliable for providing thermochemical data on CH activation. In relation with this, the relationship between the MC and HC bond enthalpies is discussed. Recent computational studies with more realistic models have revealed how ligands, bases, and other additives can assist CH activation and, in some cases, improve selectivity. These studies have shown that the metal center is not the only actor in CH activation. In the following part of the chapter, CH oxidation by inorganic and bioinorganic systems is described. In these systems, the rebound pathway, which is based on the homolytic cleavage of the CH bond, is often the mechanism of choice. A selection of representative cases is described, including bare metal-oxygen systems, the Fenton chemistry, and the Shilov reaction. In the last section, CH activation by iron, manganese, and copper biomimetic species is discussed. In these systems, the spin state often plays a key role in the reactivity of the active species. © 2013 Elsevier Ltd. All rights reserved.
    Original languageEnglish
    Title of host publicationComprehensive Inorganic Chemistry II (Second Edition): From Elements to Applications
    Pages695-726
    Number of pages31
    Volume9
    DOIs
    Publication statusPublished - 1 Aug 2013

    Keywords

    • 1,2-Addition
    • Bare metal-oxygen
    • Biomimetic
    • CH bond activation
    • Catalysis
    • Chelate-, base-, and ligand-assisted
    • Density functional theory (DFT)
    • Energy profiles
    • Fenton chemistry
    • Kinetics
    • Molecular recognition
    • Organometallic
    • Oxidative addition
    • Quantum mechanics (QM)
    • Quantum mechanics/molecular mechanics (QM/MM)
    • Reaction mechanisms
    • Rebound mechanism
    • Selectivity
    • Shilov reaction
    • Theoretical and computational chemistry
    • Thermochemistry
    • σ-Bond metathesis
    • σ-CAM

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