Recent computational studies on transition‐metal carbon–hydrogen bond activation of alkanes

Abstract

This review on computational studies of transition-metal promoted CAH activation of light linear alkanes will cover computational work published since 2010, following upon seminal reviews by Niu and Hall (Chem. Rev. 2000, 100, 353), Vastine and Hall (Coord. Chem. Rev. 2009, 253, 1202), and Balcells et al. (Chem. Rev. 2010. The computational studies are surveyed in terms of the mechanistic nature of the CAH activation step (oxidative addition, r-bond metathesis, 1,2 addition, or electrophilic activation), the type of CAH bond being activated (primary or secondary), and the effect of metal, ligand, and alkane size on the reaction process. In addition to the primary focus on theoretical mechanistic investigations via calculated thermodynamics and kinetics, this review aims to bridge the computational and experimental observations and to highlight the insights that computational chemistry delivers to understanding the nature of CAH activation of linear alkanes mediated by transition metals.bond activation, carbon hydrogen bond, density functional 1 | I N TR ODU C TI ON Toward a deeper understanding of the mechanisms of organometallic reactions and catalysis, computational chemistry has long been recognized as a useful tool to characterize reactive species especially when data on such species are extremely difficult or impossible to obtain experimentally, such the geometric and electronic structure of transition states (TS). The computationally derived potential energy surfaces (PES) not only provides thermodynamic energetics that can be correlated with the experimental kinetics, but also provides insight into the structural nature of the reaction by locating the reactants, intermediates, and products connected by the TSs, and thus, delineates the full reaction mechanism in terms of bondbreaking and bond-forming steps, which may facilitate reaction design to improve the reactivity and selectivity. [1] Several reviews published at the end of the last decade [2][3][4][5][6][7] have shown the progress that computational chemistry has made to the field of CAH bond activation, where the mechanistic interpretation of the activation step has been enhanced to show how the active mechanism for a specific scenario can depend subtly on the metal, the metal's oxidation state, the ligand set, and the substrate. Furthermore, some remarkable improvements have been made in computational methodologies that have profoundly impacted the modeling of transition-metal reactivity.Although density functional theory (DFT) with the hybrid B3LYP functional is often utilized for theoretical investigations of the structure and reactivity of organometallic complexes, the deficiencies of this functional are not negligible for thermochemistry, especially for situations where dispersion interactions are important. [8] Nowadays, dispersion interactions can be treated by adding explicit dispersion corrections by Grimme, [9] to the functional, such as B97D, [10] xB97X-D, [11] or B3LYP-D3BG, [9a] or by employing a Minnesota functional, like M06 or it...

Tetrylenes: Electronic Structure, Stability, Reactivity, and Ligand Properties—A Comparative DFT Study

“…The same C - and A + C -type tetrylenes are the strongest electron donors in complexes. Strong electron-donating ligands are of particular interest for the construction of metal complexes for the activation of challenging substrates such as aliphatic and aromatic C–H bonds. − …”