Cyclic(silyl)(amino)carbenes as Ambiphilic Platforms for Small-Molecule Activation and Skeletal Si-C Bond...

Silicon incorporation was computationally explored as a strategy to tune the electronic structure and reactivity of cyclic(alkyl)(amino)carbene (CAAC)-derived frameworks. Density functional theory calculations of cyclic(silyl)(amino)carbenes (CSiACs) show that an ortho-silicon unit raises the highest occupied molecular orbital, stabilizes the accessible acceptor orbital, and narrows the relevant donor-acceptor orbital separation, leading to enhanced ambiphilic character. This electronic modulation lowers the calculated activation barriers for representative small molecules, including CO, H2, NH3, and N2. Among these reactions, NH3 activation exhibits a particularly notable pathway: initial N-H activation is followed by NH2 migration/Si-N bond formation and intramolecular Si-C bond insertion to afford a Si/N-containing six-membered heterocyclic product with a 1,5-diaza-2-silinane-type core. Substituent screening further identifies the C6F5-substituted CSiAC-5 model as the most favorable system for lowering the key NH2 migration barrier. These results suggest that ortho-silicon incorporation can link small-molecule activation with skeletal Si-C bond reorganization, providing a computational route to expanded Si/N-containing heterocyclic frameworks.