作者:Antoine Simonneau、Martin Oestreich
DOI:10.1038/nchem.2329
日期:2015.10
Monosilane (SiH4) is far less well behaved than its carbon analogue methane (CH4). It is a colourless gas that is industrially relevant as a source of elemental silicon, but its pyrophoric and explosive nature makes its handling and use challenging. Consequently, synthetic applications of SiH4 in academic laboratories are extremely rare and methodologies based on SiH4 are underdeveloped. Safe and controlled alternatives to the substituent redistribution approaches of hydrosilanes are desirable and cyclohexa-2,5-dien-1-ylsilanes where the cyclohexa-1,4-diene units serve as placeholders for the hydrogen atoms have been identified as potent surrogates of SiH4. We disclose here that the commercially available Lewis acid tris(pentafluorophenyl)borane, B(C6F5)3, is able to promote the release of the SiâH bond catalytically while subsequently enabling the hydrosilylation of CâC multiple bonds in the same pot. The net reactions are transition-metal-free transfer hydrosilylations with SiH4 as a building block for the preparation of various hydrosilanes. Cyclohexa-2,5-dien-1-yl groups bound to silicon act as masked SiâH bonds that can be released by the action of tris(pentafluorophenyl)borane (B(C6F5)3). In this way, hazardous SiH4 is unleashed from appropriately substituted precursors and engages in alkene hydrosilylation promoted by the same boron catalyst. The overall process is a transfer hydrosilylation of alkenes with monosilane.
甲硅烷(SiH4)的性质远不如其碳类似物甲烷(CH4)稳定。它是一种无色气体,在工业上作为元素硅的来源具有重要意义,但其易燃易爆的特性使得其处理和使用颇具挑战性。因此,SiH4在学术实验室的合成应用极为罕见,基于SiH4的方法学也尚未充分发展。寻找安全可控的替代方案以取代氢硅烷的取代重分配方法是可取的,而含有环己-2,5-二烯基团的环己-1,4-二烯单元作为氢原子的占位符的硅烷已被确认为SiH4的有效替代品。我们在此揭示,商业上可获得的Lewis酸三(五氟苯基)硼烷,B(C6F5)3,能够催化释放Si–H键,随后在同一反应器中实现C–C多重键的氢硅化反应。净反应是一种无过渡金属参与的转移氢硅化反应,其中SiH4作为制备各种氢硅烷的构建单元。与硅原子结合的环己-2,5-二烯基团作为掩蔽的Si–H键,可以通过三(五氟苯基)硼烷(B(C6F5)3)的作用释放出来。通过这种方式,危险物质SiH4从适当取代的前体中释放出来,并在同一硼催化剂的促进下参与烯烃的氢硅化反应。整个过程是一种烯烃的单硅烷转移氢硅化反应。