Huynh Han Vinh
Department of Chemistry, Faculty of Science , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Republic of Singapore.
Chem Rev. 2018 Oct 10;118(19):9457-9492. doi: 10.1021/acs.chemrev.8b00067. Epub 2018 Mar 30.
N-Heterocyclic carbenes (NHCs) have become without doubt one of the most exciting and popular species in chemical science due to the ease of their preparation and modularity in stereoelectronic properties. Numerous types of NHCs have been prepared, and various experimental methodologies have been proposed for the study of their electronic properties in order to rationalize reactivities observed. The objective of this article is to provide a comprehensive overview of the most common and popular ones among them. In particular, these include the nickel(0)-based TEP, its rhodium(I) and iridium(I) variants, LEP and related electrochemical methods, the palladium(II)-based HEP, phosphinidene- and selenourea-based methods, as well as the use of direct J(C-H) coupling constants of the precarbene carbon in azolium salts. Each individual method and the underlying principle of detection it utilizes will be critically discussed in terms of strength and weakness. In addition, comprehensive amounts of data from various NHCs are compiled for the purpose of comparison. These are also meant to help the scientist in better understanding their own research data and possibly providing directions for their future research, which rely on the unique electronic properties of NHCs.
由于氮杂环卡宾（NHCs）易于制备且立体电子性质具有模块化特点，它们无疑已成为化学科学中最令人兴奋且最受欢迎的物种之一。人们已制备出多种类型的NHCs，并提出了各种实验方法来研究其电子性质，以便对观察到的反应活性做出合理的解释。本文的目的是对其中最常见且最受欢迎的方法进行全面概述。特别地，这些方法包括基于镍（0）的TEP、其铑（I）和铱（I）变体、LEP及相关电化学方法、基于钯（II）的HEP、基于磷烯和硒脲的方法，以及利用唑盐中前卡宾碳的直接J（C-H）耦合常数的方法。将从优缺点方面对每种单独的方法及其所利用的检测基本原理进行批判性讨论。此外，还收集了来自各种NHCs的大量数据用于比较。这些数据也旨在帮助科学家更好地理解他们自己的研究数据，并可能为他们未来依赖NHCs独特电子性质的研究提供方向。
