Silicon and Oxygen's Bond of Affection: An Acyclic Three-Coordinate Silanone and Its Transformation to an Iminosiloxysilylene

A long-term dream comes true: An acyclic, neutrally charged silanone at last! Here, we report on the first examples of isolable acyclic, neutral, three-coordinate silanones 2 with indefinite stability as solids and lifetimes in solution of up to 2 days. The electronic properties of the Si=O bond were investigated via DFT calculations and revealed the π-donating N-heterocyclic imino (NHI) and σ-donating silyl groups as key factors for their enhanced stability. Besides initial reactivity studies of 2 toward CO₂ and methanol, different isomerization pathways depending on the silyl substitution pattern were found. For 2a (R = TMS), a 1,3-silyl shift gave an intermediary disilene, which was trapped as unique NHC-disilene adduct 6. For the more stable silanone 2b (R = t-Bu), a selective transformation to the first reported room temperature stable, acyclic, two-coordinate N,O-silylene 7 exhibiting a fascinating siloxy ligand was observed. Both compounds were fully characterized experimentally and their bonding features were analyzed by theoretical calculations.