Dissecting Reaction Paths with the Independent Gradient Model: The Case of a Key Reductive Elimination Step at...

Area of Science:

• * Quantum Chemistry
• * Computational Chemistry
• * Inorganic Chemistry

Background:

• * The Independent Gradient Model (IGM) is a computational tool used to analyze electron density (ED) gradients.
• * Understanding reaction mechanisms in metallacyclic complexes is crucial for catalysis.
• * Concerted reductive elimination is a key reaction pathway in organometallic chemistry.

Purpose of the Study:

• * To investigate the electronic structure variations of a cobalt complex during reductive elimination using IGM.
• * To identify the role of ligands, specifically the Cp* ligand, in the reaction mechanism.
• * To analyze the interaction signatures and electron density changes throughout the reaction coordinate.

Main Methods:

• * Application of the Independent Gradient Model (IGM) to analyze electron density (ED) gradients.
• * Calculation of Intrinsic Reaction Coordinates (IRC) for a metallacyclic cobalt complex.
• * Evaluation of the IGM interfragment Δginter score and the degree of interaction (DOI(Co)).

Main Results:

• * The Cp* ligand acts as an electron density reservoir, supplementing the cobalt center during reductive elimination.
• * Significant electronic changes were observed, indicated by variations in the DOI(Co) score.
• * Peaks in DOI(Co) occurred around, but not at, the transition state (TS), suggesting transient structures play a key role.

Conclusions:

• * The IGM effectively reveals ligand-metal interactions and electronic structure changes during reactions.
• * The Cp* ligand's role as an electron density reservoir was confirmed.
• * Counterintuitively, major electronic restructuring does not occur precisely at the transition state but in preceding or succeeding transient structures.