Highly Electron-Deficient Carbon, Boron and Silicon Compounds

在化学系化学合成项目的支持下，加州大学圣地亚哥分校化学与生物化学系的Guy Bertrand教授正在研究高度缺电子的碳、硼和硅化合物。通常，碳、硼和硅等原子包含一个完整的八隅体，即当它们与其他原子形成化合物时，被八个电子包围。该项目旨在隔离只拥有4或5个周围电子的物种。人们认为这些化合物本身就不稳定，这阻碍了对它们的分离。然而，通过连接专门设计来稳定电子缺乏的基团，将制备出具有这些非常低电子计数的稳定化合物。这些稳定版本的可用性提供了对化学反应机制的更好理解，并为新的应用开辟了道路。例如，具有六价电子的碳化合物已成为化学中的有力工具，并在医学和材料科学中得到了应用。该项目将制备碳、硅和硼，它们的价电子少至4个。虽然这项工作在本质上是基础性的，但最终的物种肯定会得到大量的应用，并使整个社会受益。PI实验室是加州大学圣地亚哥分校和法国国家科学研究中心的合资企业。它旨在促进加州大学圣地亚哥分校与欧洲大学之间的本科生和研究生交流。最近分离出的一种单取代碳烯，即氨基碳烯（R2NCH），证明了氨基取代基可以抑制六电子物质的固有不稳定性。因此，Bertrand团队认为，利用这一原理，可以分离出具有主族元素只有5个价电子甚至4个价电子的化合物。将制备单配位碳化合物，即氨基碳炔（R2NC：●）和氨基碳阳离子（R2NC:+），以及等电子硼炔自由基阴离子（R2NB：●-）和硼炔（R2NB:）。除了单坐标系外，碳自由基的二配位阳离子（R2C+●）和碳离子（R2C++ +）也成为了研究的目标，它们在碳原子周围也只有5个和4个价电子，分别是碳的一个和两个电子氧化形式。一旦这些缺乏电子的物种被掌握，它们的合成效用将被探索。举例来说，碳化R2C++可以作为强路易斯酸，包括在受挫的路易斯对化学中找到应用。这个项目是物理，有机，无机和有机金属化学的联系，非常适合各级化学家的教育。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Synthesis Program of the Chemistry Division, Professor Guy Bertrand of the Department of Chemistry and Biochemistry at the University of California – San Diego, is studying highly electron-deficient carbon, boron and silicon compounds. Usually atoms such as carbon, boron, and silicon contain a full octet, i.e. are surrounded by eight electrons when they form compounds with other atoms. This project seeks to isolate species that only possess 4 or 5 surrounding electrons. The isolation such compounds has been impeded by the belief that they are inherently unstable. However, by attaching groups that are specially designed to stabilize electron deficiencies stable compounds with these very low electron counts will be prepared. The availability of these stable versions provides a better understanding of chemical reaction mechanisms and opens the way for new applications. As an example, carbon compounds with six-valence electrons have become powerful tools in chemistry and have found medicinal and material science applications. This project will prepare carbon, silicon and boron with as few as four valence electrons. Although the work is fundamental in nature, the resulting species will certainly find a plethora of applications and benefit society at large. The laboratory of the PI is a joint venture between UCSD and the French CNRS. It serves to promote the exchange of undergraduates and graduates between UCSD and European Universities. The recent isolation of a monsubstituted carbene, namely an aminocarbene (R2NCH), demonstrates that an amino substituent can tame the intrinsic instability of a six-electron species. Therefore, the Bertrand team believes that using this principle compounds featuring a main-group element with only five- and even four-valence electrons can be isolated. Monocoordinated carbon compounds, namely amino carbynes (R2NC:●) and amino carbocations (R2NC:+), as well as the isoelectronic borylene radical anions (R2NB:●-) and borylenes (R2NB:) will be prepared. Apart from monocoordinate systems, dicoordinate carbon radical cations (R2C+●) and carbodications (R2C++), which also feature only five and four valence-electrons around the carbon atom and are the one and two electron oxidized forms of a carbene, respectively, are also being targeted. Once these electron-deficient species are in hand, their synthetic utility will be explored. As an illustration, carbodications R2C++ could find applications as strong Lewis acids, including in frustrated Lewis pair chemistry. This project which is at the nexus of physical, organic, inorganic and organometallic chemistry is well suited to the education of chemists at all levels.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.