Challenges in modelling homogeneous catalysis: new answers from ab initio molecular dynamics to the controversy over the Wacker process

Abstract

We present here a review on the mechanistic studies of the Wacker process stressing the long controversy about the key reaction steps. We give an overview of the previous experimental and theoretical works on the topic. Then we describe the importance of the most recent Ab Initio Molecular Dynamics (AIMD) calculations in modelling organometallic reactivity in water. As a prototypical example of homogeneous catalytic reactions, the Wacker process poses serious challenges to modelling. The adequate description 10 of the multiple role of the water solvent is very difficult by using static quantum chemical approaches including cluster and continuum solvent models. In contrast, such reaction systems are suitable for AIMD, and by combining with rare event sampling techniques, the method provides reaction mechanisms and the corresponding free energy profiles. The review also highlights how AIMD has helped to obtain novel understanding of the mechanism and kinetics of the Wacker process.

DFT calculations on the mechanism of copper-catalysed tandem arylation–cyclisation reactions of alkynes and diaryliodonium salts

“…We decided to characterise this step by the free energy level of the intermediate: 17.6 kcal/mol. There are two reasons behind this choice: i) the preceding and subsequent barriers were computed to be very close in energy to that of this structure; ii) one of the participants of this step is the solvent EtOAc molecule, i.e., the solvent plays a two-fold role: it is a reactant and a solvating agent; as it is known, such situations are difficult to describe by implicit solvent models [45]. The intermediate formed in this step ( I 1 ) is stabilised at 5.7 kcal/mol.…”

Palladium-Catalyzed Anti-Markovnikov Oxidation of Aromatic and Aliphatic Alkenes to Terminal Acetals and Aldehydes

“…[1][2][3][4][5][6][7][8][9] Pd/Cu-catalyzed Wacker-type oxidation is a recognized method for synthesizing carbonyl compounds from alkenes. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] The Wacker-type oxidation generally proceeds with Markovnikov selectivity to afford methyl ketones from terminal alkenes, and AM Wacker-type oxidation is relatively rare (Scheme 1). [1][2][3] The AM Wacker-type oxidation provides a complementary method for synthesizing aldehydes from terminal alkenes, compared to hydroformylation and oxidative cleavage such as ozonolysis, where the former provides aldehydes with the same carbon chain length as the starting alkenes, unlike the latter two reactions.…”

Operando Modeling of Multicomponent Reactive Solutions in Homogeneous Catalysis: from Non‐standard Free Energies to Reaction Network Control

“…Although traditionally conversion and catalyst development has been the domain of experimental investigations, the input from the computational modeling has been steadily increasing since the 1980s. The benefits of the synergy between theory and experiment to deliver molecular level insights into complex chemical transformations have become apparent during the last two decades . The development of the predictive theoretical approaches to enable a computer‐based search for the optimal conditions and composition of the reaction mixture for a given chemical transformation to replace tedious and costly experimental work is one of the key challenges for applied computational chemistry today.…”