Hexene hydrogenation catalysed by the complex monohydrid complexes: A DFT study of associated vs dissociated pathways
Sofiene Achour1, Zied Hosni2, Bahoueddine Tangour1
1University of Tunis El Manar, Research Unit of Modeling in Fundamental Sciences and Didactics, IPEIEM, PO Box 254, El Manar 2, 2096, Tunis, Tunisia.
Journal of Molecular Graphics & Modelling
|March 23, 2020
Summary
This DFT study reveals ruthenium catalysts efficiently hydrogenate hexene via dissociative pathways, with phosphine release being the most probable route. Different ruthenium catalysts show similar energetic barriers for this key reaction step.
Area of Science:
- Organometallic Chemistry
- Catalysis
- Computational Chemistry
Background:
- Hexene hydrogenation is a crucial industrial process.
- Ruthenium complexes are effective catalysts for hydrogenation reactions.
- Understanding reaction mechanisms is key to catalyst optimization.
Purpose of the Study:
- To elucidate the mechanism of hexene hydrogenation catalyzed by ruthenium (II) monohydride complexes.
- To compare the feasibility of dissociative and associative catalytic pathways.
- To investigate the influence of different ligands on the reaction mechanism.
Main Methods:
- Density Functional Theory (DFT) calculations were employed.
- Detailed reaction pathways for dissociative and associative mechanisms were explored.
- Activation energies for key steps, particularly hydrogen migration, were computed.
Main Results:
- The dissociative pathway involving phosphine release (Pathway A) is identified as the most probable mechanism.
- Both dissociative (A, B) and associative (D) pathways exhibit comparable activation energies.
- Ligand substitution on the ruthenium center (e.g., PMe3, PCy3, IMes) showed minimal impact on energetic barriers.
Conclusions:
- The dissociative mechanism, initiated by phosphine release, is favored for hexene hydrogenation over ruthenium catalysts.
- Multiple reaction pathways can occur simultaneously, with the dissociative route dominating.
- The study provides a detailed mechanistic understanding crucial for designing improved hydrogenation catalysts.
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