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From Si(II) to Si(IV) and Back: Reversible Intramolecular Carbon–Carbon Bond Activation by an Acyclic Iminosilylene
- Wendel, Daniel, Porzelt, Amelie, Herz, Fabian A. D., Sarkar, Debotra, Jandl, Christian, Inoue, Shigeyoshi, Rieger, Bernhard
- Journal of the American Chemical Society 2017 v.139 no.24 pp. 8134-8137
- carbon dioxide, catalytic activity, chemical bonding, density functional theory, ethylene, hydrogen, ligands, silicon, silicon compounds, temperature
- Reversibility is fundamental for transition metal catalysis, but equally for main group chemistry and especially low-valent silicon compounds, the interplay between oxidative addition and reductive elimination is key for a potential catalytic cycle. Herein, we report a highly reactive acyclic iminosilylsilylene 1, which readily performs an intramolecular insertion into a C═C bond of its aromatic ligand framework to give silacycloheptatriene (silepin) 2. UV–vis studies of this Si(IV) compound indicated a facile transformation back to Si(II) at elevated temperatures, further supported by density functional theory calculations and experimentally demonstrated by isolation of a silylene–borane adduct 3 following addition of B(C₆F₅)₃. This tendency to undergo reductive elimination was exploited in the investigation of silepin 2 as a synthetic equivalent of silylene in the activation of small molecules. In fact, the first monomeric, four-coordinate silicon carbonate complex 4 was isolated and fully characterized in the reaction with carbon dioxide under mild conditions. Additionally, the exposure of 2 to ethylene or molecular hydrogen gave silirane 5 and Si(IV) dihydride 6, respectively.