Department of Chemistry, Smith College , Northampton, Massachusetts 01063, United States.
J Am Chem Soc. 2016 Jul 13;138(27):8639-52. doi: 10.1021/jacs.6b04962. Epub 2016 Jul 1.
Surface passivation has enabled the development of silicon-based solar cells and microelectronics. However, a number of emerging applications require a paradigm shift from passivation to functionalization, wherein surface functionality is installed proximal to the silicon surface. To address this need, we report here the use of persistent aminocarbenes to functionalize hydrogen-terminated silicon surfaces via Si-H insertion reactions. Through the use of model compounds (H-Si(TMS)3 and H-Si(OTMS)3), nanoparticles (H-SiNPs), and planar Si(111) wafers (H-Si(111)), we demonstrate that among different classes of persistent carbenes, the more electrophilic and nucleophilic ones, in particular, a cyclic (alkyl)(amino)carbene (CAAC) and an acyclic diaminocarbene (ADAC), are able to undergo insertion into Si-H bonds at the silicon surface, forming persistent C-Si linkages and simultaneously installing amine or aminal functionality in proximity to the surface. The CAAC (6) is particularly notable for its clean insertion reactivity under mild conditions that produces monolayers with 21 ± 3% coverage of Si(111) atop sites, commensurate with the expected maximum of ∼20%. Atomic force and transmission electron microscopy, nuclear magnetic resonance, X-ray photoelectron, and infrared spectroscopy, and time-of-flight secondary ion mass spectrometry provided evidence for the surface Si-H insertion process. Furthermore, computational studies shed light on the reaction energetics and indicated that CAAC 6 should be particularly effective at binding to silicon dihydride, trihydride, and coupled monohyride motifs, as well as oxidized surface sites. Our results pave the way for the further development of persistent carbenes as universal ligands for silicon and potentially other nonmetallic substrates.
表面钝化使得基于硅的太阳能电池和微电子技术得以发展。然而，一些新兴应用需要从钝化到功能化的范式转变，即在硅表面附近安装表面功能。为了满足这一需求，我们在此报告了使用持久碳烯通过 Si-H 插入反应来功能化氢终止的硅表面。通过使用模型化合物（H-Si(TMS)3 和 H-Si(OTMS)3）、纳米颗粒（H-SiNPs）和平面 Si(111) 晶片（H-Si(111)），我们证明在不同类别的持久碳烯中，更具亲电性和亲核性的，特别是环状（烷基）（氨基）碳烯（CAAC）和非环状二氨基碳烯（ADAC），能够在硅表面的 Si-H 键中插入，形成持久的 C-Si 键，并在表面附近同时安装胺或亚胺官能团。CAAC（6）特别引人注目，因为它在温和条件下具有清洁的插入反应性，在 Si(111) 表面上产生了 21±3%覆盖率的单层，与预期的最大值约为 20%相当。原子力和透射电子显微镜、核磁共振、X 射线光电子和红外光谱以及飞行时间二次离子质谱提供了表面 Si-H 插入过程的证据。此外，计算研究揭示了反应的能量学，并表明 CAAC 6 应该特别有效地与硅二氢化物、三氢化物和耦合单氢化物基以及氧化表面位点结合。我们的结果为进一步开发持久碳烯作为硅和潜在其他非金属基底的通用配体铺平了道路。
