WACKER-Chair of Macromolecular Chemistry, ∥WACKER-Institute of Silicon Chemistry, ‡Catalysis Research Center, Technische Universität München , Lichtenbergstraße 4, 85748 Garching bei München, Germany.
J Am Chem Soc. 2017 Jun 21;139(24):8134-8137. doi: 10.1021/jacs.7b05136. Epub 2017 Jun 12.
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(CF). 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.
反转性对于过渡金属催化至关重要，但对于主族化学，特别是低价硅化合物来说，氧化加成和还原消除之间的相互作用对于潜在的催化循环至关重要。在此，我们报道了一种高反应性的非环亚氨基硅基亚硅基，它可容易地进行分子内插入其芳族配体骨架中的 C=C 键，得到硅杂环庚三烯（硅叶立德）2。对这种 Si(IV)化合物的紫外可见研究表明，在高温下很容易转化回 Si(II)，这进一步得到了密度泛函理论计算的支持，并通过在添加 B(CF )后分离得到硅烯-硼烷加合物 3 得到了实验验证。3 这种易于进行还原消除的趋势在研究硅叶立德 2 作为硅烯在小分子活化中的合成等价物时得到了利用。事实上，在温和条件下与二氧化碳反应，首次分离并充分表征了单体四配位硅碳酸酯配合物 4。此外，将 2 暴露于乙烯或分子氢中，分别得到硅烷 5 和 Si(IV)二氢化物 6。
