Electrophilicity of Hoveyda‐Grubbs Olefin Metathesis Catalysts as the Driving Force that Controls Initiation Rates

Abstract

The dissociative mechanism of initiation for a series of Hoveyda-Grubbs type metathesis catalysts modified at the para and meta positions in the isopropoxybenzylidene ligand is investigated by means of DFT calculations. The electron donating/withdrawing capacity of the ligand was screened through the incorporation of various substituents such as halogens, nitro, alkoxides, ketones, esters, amines, and amides. Variations in structural parameters, energy barriers for the RuÀ O bond dissociation, and RuÀ O bond strength were examined as a function of the Hammett constant. It was found that electronic properties of the catalysts such as chemical potential, hardness, and electrophilicity correlate linearly with the dissociative energy barriers. These findings enable a systematic rationalization and prediction of rate of precatalyst initiation through the calculation of only the HOMO-LUMO gap of catalysts, as the faster the initiation, the more electrophilic the catalyst.

Different Reaction Modes Operating in ansa‐Half‐Sandwich Magnesium Catalysts

“…For instance, following the same hydroacetylenation, we calculated an absolute δE 2 of 34.9 kcal/mol for tetra‐aminated Cp, higher than the single substitution with NMe 2 in position 3 of Cp (32.4 kcal/mol). A comprehensive exploration of how electron‐donating or electron‐withdrawing effects deteriorate in Ru‐based catalysts based on phenyl substituents has been previously published [62] …”

“…A comprehensive exploration of how electron-donating or electron-withdrawing effects deteriorate in Ru-based catalysts based on phenyl substituents has been previously published. [62]…”

H-Bonding leading to latent initiators for olefin metathesis polymerization

“…3, we proceeded to do a simple analysis of the frontier molecular orbitals together with conceptual DFT, 65 with the surprise that even though it is about similar stability, corroborated by the almost identical chemical hardness for species A for all systems, the same does not happen with the chemical potential, nor with electrophilicity, but contrarily to what was predicted recently by Martínez and Trzaskowski with Grubbs-Hoveyda type catalysts, where the higher the electrophilicity the higher the reactivity was. 66 Thus, a simple NH group modulates the reactivity, making systems 1 and 2 more electrophilic, explained by similar stabilization of both the HOMO and the LUMO. To unveil how the H-bonds of the halides and the organic moiety of the imine ligand trans to the NHC affect the system, 3D and 2D NCI plots in Fig.…”

An Anthracene-Thiolate-Ligated Ruthenium Complex: Computational Insights into Z-Stereoselective Cross Metathesis

“…However, the inclusion of D3 corrections to M06 was demonstrated to enhance the results for catalyzed olefin metathesis, particularly in treating weak interactions . Furthermore, the computational approach we chose has previously been benchmarked against experimental data. , …”