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Structural Flexibility is a Decisive Factor in FLP Dihydrogen Cleavage with Tetrahedral Lewis Acids: A Silane Case
Thaddäus Thorwart1, Lutz Greb1
1Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|June 10, 2024
Summary
Frustrated Lewis pairs (FLPs) activate dihydrogen. This study reveals how Lewis acid flexibility, not just transition state energies, impacts FLP reactions, explaining previously puzzling experimental results.
Area of Science:
- Organometallic Chemistry
- Computational Chemistry
- Catalysis
Background:
- Dihydrogen activation by frustrated Lewis pairs (FLPs) is a key reaction.
- Trigonal-planar Lewis acids are well-studied, but tetrahedral Lewis acids show limited success and discrepancies with computed results.
Purpose of the Study:
- To computationally investigate factors influencing dihydrogen activation by FLPs.
- To compare silicon/nitrogen FLPs with boron/phosphorous FLPs.
- To understand discrepancies between computed and experimental results for tetrahedral Lewis acids.
Main Methods:
- Computational investigation using large ensemble sampling of encounter complexes.
- Analysis of deformation energies and the activation strain model.
- Comparison of silicon/nitrogen FLP with boron/phosphorous FLP.
Main Results:
- Lewis acid structural flexibility significantly influences preexponential terms beyond transition state energies.
- Identified the origin of "overfrustration" in FLP reactions.
- Demonstrated that structural constraints in Lewis acids are crucial for activating weak donor substrates.
Conclusions:
- Structural flexibility of Lewis acids is a critical, previously overlooked factor in dihydrogen activation by FLPs.
- Provides a refined mechanistic understanding of FLP reactivity, particularly for tetrahedral Lewis acids.
- Highlights the importance of Lewis acid design for controlling catalytic activity.
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