Lewis Base Catalyzed Selective Chlorination of Monosilanes

Area of Science:

• Organosilicon Chemistry
• Synthetic Chemistry
• Reaction Mechanism Studies

Background:

• Bifunctional monosilanes are valuable synthetic intermediates.
• Existing methods for their synthesis can lack selectivity or require harsh conditions.
• Controlled introduction of silicon-chlorine bonds is crucial for further functionalization.

Purpose of the Study:

• To report a facile and highly selective synthesis of bifunctional monosilanes (R2SiHCl, RSiHCl2, RSiH2Cl).
• To investigate a novel mode of silicon-hydride (Si-H) bond activation.
• To elucidate the reaction mechanisms involved in the chlorination of silanes.

Main Methods:

• Chlorination of dialkylsilanes (R2SiH2) and alkylsilanes (RSiH3) using concentrated HCl in ether solutions.
• Control of reaction parameters such as temperature and time for selective Si-Cl bond formation.
• Combined experimental and computational studies to understand reaction pathways and intermediates.

Main Results:

• Successful synthesis of various bifunctional monosilanes with high selectivity.
• Demonstration of Lewis base-assisted Si-H bond activation (ethers, amines, phosphines, chloride ions).
• Identification of alcohol assistance via hydrogen-bond networks as an effective and selective alternative.

Conclusions:

• A preparatively accessible and selective method for synthesizing key bifunctional monosilanes has been established.
• A new mechanism involving Lewis base or alcohol assistance for Si-H bond activation in chlorination reactions was uncovered.
• The methodology avoids the formation of undesired alkoxysilanes or siloxanes under moderate conditions, enhancing its utility.