Frustrated Lewis Pairs Comprising Nitrogen Lewis Acids for Si-H Bond Activation

Area of Science:

• Organic Chemistry
• Organometallic Chemistry

Background:

• N-heterocyclic nitrogen Lewis acids are emerging compounds in organic chemistry.
• Previous work demonstrated their ability to form Lewis adducts with Lewis bases.

Purpose of the Study:

• To synthesize and characterize a novel frustrated Lewis pair (FLP) capable of cleaving silicon-hydrogen (Si-H) bonds.
• To develop a more effective nitrenium-based Lewis acid for enhanced reactivity.

Main Methods:

• Synthesis of a triazinium-based Lewis acid and its combination with tBu3P to form a FLP.
• Development and characterization of a new nitrenium-based Lewis acid with superior Lewis acidity.
• Experimental and computational confirmation of Lewis acidity.
• Reaction of the FLP with PhSiH3 to cleave the Si-H bond.
• Characterization of the resulting N-H triazane product using multinuclear NMR and single-crystal X-ray crystallography.

Main Results:

• Initial attempts with a triazinium-based Lewis acid yielded low amounts of product due to insufficient Lewis acidity.
• A newly synthesized nitrenium-based Lewis acid exhibited significantly enhanced Lewis acidity.
• The improved FLP achieved quantitative yield in cleaving the Si-H bond of PhSiH3.
• An unprecedented N-H triazane was successfully synthesized and fully characterized.

Conclusions:

• A novel class of N-H triazanes has been synthesized.
• These N-H triazanes demonstrate potential for participation in hydride transfer reactions.
• The developed nitrenium-based Lewis acid and FLP represent a significant advancement in Si-H bond activation.