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Updated: Jul 19, 2025
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Characterizing Lewis Pairs Using Titration Coupled with In Situ Infrared Spectroscopy
Published on: February 20, 2020
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Electron-deficient cyclopropenium cations as Lewis acids in FLP chemistry
Dipendu Mandal1,2, Zheng-Wang Qu3, Stefan Grimme3
1Institute of Drug Discovery Technology, Ningbo University, Ningbo 315211, Zhejiang, China.
Chemical Communications (Cambridge, England)
|August 11, 2023
Summary
Electron-deficient cyclopropenium cations exhibit Lewis acidity, forming adducts and frustrated Lewis pairs (FLPs). These FLPs enable new C-C bond formation via additions to alkynes or deprotonation, expanding FLP chemistry applications.
Area of Science:
- Organic Chemistry
- Organometallic Chemistry
- Computational Chemistry
Background:
- Cyclopropenium cations, despite π-electron presence, can be Lewis acidic.
- Electron-deficient substituents enhance the Lewis acidity of cyclopropenium cations.
Purpose of the Study:
- To investigate the Lewis acidity of cyclopropenium cations with electron-deficient substituents.
- To explore the reactivity of these cations with phosphines, including the formation of frustrated Lewis pairs (FLPs).
- To demonstrate the application of FLP chemistry in reactions involving delocalized π-cations.
Main Methods:
- Computational examination of chloride and electron affinities.
- Experimental studies of Lewis acid-base adduct formation with phosphines.
- Investigation of FLP reactions with alkynes and alkyne deprotonation.
Main Results:
- Cyclopropenium cations form Lewis acid-base adducts with triphenylphosphine (PPh3).
- Sterically demanding phosphines lead to the formation of frustrated Lewis pairs (FLPs).
- FLPs react with alkynes via addition or deprotonation, forming new C-C bonds.
Conclusions:
- Electron-deficient cyclopropenium cations are effective Lewis acids.
- Frustrated Lewis pair chemistry can be extended to delocalized π-cations.
- This work provides new synthetic routes for C-C bond formation using cyclopropenium cations and FLPs.
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