The initiation mechanisms for surface hydrosilylation with 1-alkenes

Area of Science:

• Surface Chemistry
• Materials Science
• Computational Chemistry

Background:

• Hydrosilylation is a key reaction for forming substituted silanes in solution, typically requiring a catalyst.
• A similar reaction, thermal hydrosilylation, forms covalent organic monolayers on hydrogen-terminated silicon surfaces.
• Surface hydrosilylation exhibits remarkably low activation energy barriers compared to solution-phase reactions, with ongoing mechanistic debate.

Purpose of the Study:

• To elucidate the mechanism of thermal hydrosilylation on silicon surfaces.
• To investigate the role of visible light and thermal excitation in overcoming activation barriers.
• To explain the low activation energy barriers observed for surface hydrosilylation.

Main Methods:

• Constrained molecular dynamics simulations.
• Density functional theory (DFT) framework.
• Analysis of free energy activation barriers for hydrogen abstraction and alkene insertion.

Main Results:

• Visible light or thermal excitation can overcome the free energy activation barrier for hydrogen abstraction from silicon by alkenes.
• A concerted hydrogen transfer mechanism facilitates the insertion of 1-alkenes into surface Si-H bonds.
• The study provides a mechanistic explanation for the efficient formation of covalent organic monolayers via surface hydrosilylation.

Conclusions:

• The findings clarify the mechanism of surface hydrosilylation, highlighting the roles of light and heat.
• This research offers insights into the formation of functionalized silicon surfaces for materials applications.
• The computational approach provides a valuable tool for understanding surface reactions with low activation barriers.