Dehydrogenative Coupling of Hydrosilanes With Alcohols and Amines: A Concerted Asynchronous Mechanism With an Early Hidden Reaction Intermediate

The dehydrogenative coupling of hydrosilanes with protic nucleophiles offers a promising route for hydrogen generation under mild conditions with no added catalysts. The current work is a theoretical investigation of the cross coupling of hydrosilanes and methanol, methylamine and 2‐(methylamino)‐ethanol (MEA), with particular emphasis on the reaction mechanism and consecutive hydride substitutions by the O‐ and N‐containing groups of MEA, in the presence of Ph 4‐n SiH n with n = 1 to 4. We employed the density functional theory (DFT) and the intrinsic reaction coordinate (IRC) technique to delineate the energy profiles and the associated reaction mechanism. All nucleophilic substitutions were found to follow a concerted asynchronous mechanism involving a hidden reaction intermediate (HRI), which occurs prior to a pentacoordinated silicon transition state. This mechanism indicates that the SiO bond formation and SiH bond cleavage precede the HH bond formation. This finding was refined by the reactive internal reaction coordinates (RIRC) analysis. For all Ph 4‐n SiH n silanes, successive (O) substitutions corresponded to decreasing activation energy, indicating that the reaction became increasingly more favorable. For example, the activation energies decreased from 17.30 to 14.94 kcal mol −1 for consecutive (O) substitutions in PhSiH 3 . In contrast, substitutions by (N) groups showed the opposite trend, with activation barriers increasing as more nitrogen‐containing ligands were introduced. These findings provide a molecular‐level understanding of experimental data reported in the literature.