Highly Electron-Deficient Carbon, Boron and Silicon Compounds

在化学系化学合成计划的支持下，加州大学圣地亚哥分校化学和生物化学系的盖伊·贝特朗教授正在研究高度缺乏电子的碳、硼和硅化合物。通常，碳、硼和硅等原子包含完整的八位组，即当它们与其他原子形成化合物时，它们被八个电子包围。这个项目试图分离出只有4到5个周围电子的物种。这种化合物的分离受到了这样一种信念的阻碍，即它们天生就不稳定。然而，通过连接专为稳定电子缺陷而设计的基团，将制备出具有这些非常低的电子计数的稳定化合物。这些稳定版本的出现有助于更好地了解化学反应机理，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经成为化学中的强大工具，并在医学和材料科学中得到了应用。该项目将用最少四个价电子制备碳、硅和硼。尽管这项工作在本质上是基本的，但由此产生的物种肯定会有过多的应用，并造福于整个社会。PI的实验室是加州大学圣地亚哥分校和法国CNRS的合资企业。它旨在促进加州大学圣迭戈分校和欧洲大学之间的本科生和毕业生的交流。最近分离的一种单取代卡宾，即氨基卡宾(R2NCH)，表明氨基取代可以驯服六电子物种的内在不稳定性。因此，伯特朗团队认为，使用这一原理，可以分离出主族元素只有五价甚至四价电子的化合物。将制备单配位碳化合物，即氨基卡宾(R2NC：)和氨基碳正离子(R2NC：+)，以及等电子的硼基阴离子(R2Nb：-)和亚乙烯(R2Nb：)。除了单坐标体系外，二配位碳自由基阳离子(R2C+)和碳阳离子(R2C++)也是目标，它们在碳原子周围也只有五个和四个价电子，分别是卡宾的一个和两个电子氧化形式。一旦这些缺乏电子的物种出现，它们的合成用途将被探索出来。例如，碳化R2C++可以作为强Lewis酸的应用，包括在受挫的Lewis对化学中。这个项目集物理、有机、无机和有机金属化学为一体，非常适合各级化学家的教育。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.