Kapp Leon, Wölper Christoph, Siera Hannah, Haberhauer Gebhard, Schulz Stephan
Institute for Inorganic Chemistry, University of Duisburg-Essen Universitätsstraße 5-7 45117 Essen Germany
Institute for Organic Chemistry, University of Duisburg-Essen Universitätsstraße 5-7 45117 Essen Germany
Chem Sci. 2024 Feb 12;15(11):4161-4170. doi: 10.1039/d3sc06842k. eCollection 2024 Mar 13.
The application of main group metal complexes in catalytic reactions is of increasing interest. Here we show that the electron-rich, acyclic metallasilylene L'(Cl)GaSiL C (L' = HC[C(Me)NDipp], Dipp = 2,6-PrCH; L = PhC(NBu)) acts as a precatalyst in the hydroboration of aldehydes with HBPin. Mechanistic studies with iso-valeraldehyde show that silylene C first reacts with the aldehyde with [2 + 1] cycloaddition in an oxidative addition to the oxasilirane 1, followed by formation of the alkoxysilylene LSiOCH[Ga(Cl)L']CHCHMe (2), whose formation formally results from a reductive elimination reaction at the Si center. Alkoxysilylene 2 represents the active hydroboration catalyst and shows the highest catalytic activity with -hexanal (reaction time: 40 min, yield: >99%, TOF = 150 h) at room temperature with a catalytic load of only 1 mol%. Furthermore, the hydroboration reaction catalysed by alkoxysilylene 2 is a living reaction with good chemoselectivity. Quantum chemical calculations not only provide mechanistic insights into the formation of alkoxysilylene 2 but also show that two completely different hydroboration mechanisms are possible.
主族金属配合物在催化反应中的应用越来越受到关注。在此我们表明，富电子的无环金属硅烯L'(Cl)GaSiL C（L' = HC[C(Me)NDipp]，Dipp = 2,6 - PrCH；L = PhC(NBu)）在醛与HBPin的硼氢化反应中作为预催化剂。用异戊醛进行的机理研究表明，硅烯C首先与醛通过[2 + 1]环加成反应，以氧化加成到氧杂硅环烷1上，随后形成烷氧基硅烯LSiOCH[Ga(Cl)L']CHCHMe（2），其形成形式上是由硅中心的还原消除反应导致的。烷氧基硅烯2代表活性硼氢化催化剂，在室温下仅以1 mol%的催化负载量对己醛表现出最高的催化活性（反应时间：40分钟，产率：>99%，TOF = 150 h⁻¹）。此外，由烷氧基硅烯2催化的硼氢化反应是具有良好化学选择性的活性反应。量子化学计算不仅为烷氧基硅烯2的形成提供了机理见解，还表明两种完全不同的硼氢化机理是可能的。
