From Si(II) to Si(IV) and Back: Reversible Intramolecular Carbon–Carbon Bond Activation by an Acyclic Iminosilylene

• Published in: Journal of the American Chemical Society 2017-06, Vol.139 (24), p.8134-8137
• Main Authors: Wendel, Daniel, Porzelt, Amelie, Herz, Fabian A. D, Sarkar, Debotra, Jandl, Christian, Inoue, Shigeyoshi, Rieger, Bernhard
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.7b05136

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.