Reversible Oxidative Addition/Reductive Elimination of a Si-H Bond with Base-Stabilized Silylenes: A Theoretical Insight.

Abstract

Although oxidative addition (OA) and reductive elimination (RE) are exceedingly important processes in organometallic chemistry, such processes are still extremely rare for main-group element species. Herein, we report a theoretical study on the reaction of phosphine-stabilized silylenes with silanes that proceeds through reversible OA/RE at room temperature. Of particular interest is that this theoretical approach highlights the important role of the ligand, which can greatly affect the kinetics and energy balance of the reaction. Indeed, in contrast to the case of free aminosilylenes, the reaction of ligand-supported silylenes proceeds in an unsynchronized manner and starts with the silylene→silane charge transfer (CT). Suitably electron-donating ligands, such as phosphines or N-heterocyclic carbenes, enhancing the CT at the transition state (TS), significantly decrease the Gibbs activation energy and the exergonic nature of the reaction, which promote the OA/RE processes. In the same way, silanes with electron-withdrawing groups also favor the CT and thus stabilize the TS. It was also computationally predicted that phosphine-stabilized silylenes should be able to activate the C-Si bond of trimethoxy(ethynyl)silane (HC≡C-Si(OMe)3 ) and that the reaction should proceed in a reversible manner under mild conditions.