Frustrated Lewis Pair (FLP) Reactivity from Carbone-BPh₃ Lewis Adduct

Area of Science:

• Organometallic Chemistry
• Main-group Chemistry
• Catalysis

Background:

• Frustrated Lewis Pairs (FLPs) are crucial for activating small molecules.
• Carbodicarbenes (fCDCs) offer a tunable carbene platform for Lewis acid-base chemistry.

Purpose of the Study:

• To systematically investigate the FLP chemistry of fCDCs with varying steric profiles and boron Lewis acids.
• To explore the reactivity spectrum from tightly bound adducts to unbound FLPs.
• To establish fCDC-borane adducts as platforms for metal-free catalysis.

Main Methods:

• Synthesis and characterization of fCDC-borane adducts.
• Variable temperature NMR spectroscopy to study dissociation and reactivity.
• Density Functional Theory (DFT) calculations to elucidate reaction mechanisms.
• Catalytic testing for small molecule activation and transformations.

Main Results:

• A range of CDC-borane systems were synthesized, showing diverse behaviors including stable adducts, reversibly dissociating adducts, and unbound FLPs.
• The most reactive adduct, 1·BPh3, demonstrated broad small molecule activation (C-H, O-H, N-H, H-B, H-Si, S-S, CO2) and catalyzed hydroboration/hydrosilylation of ketones.
• Reversible dissociation and transient encounter complex formation were identified as key to FLP reactivity.

Conclusions:

• fCDC-borane adducts represent a tunable platform for FLP-type small molecule activation.
• Steric and electronic modulation of fCDCs allows control over FLP reactivity.
• This work enables metal-free main-group catalysis with potential for diverse chemical transformations.