What Wanzlick Did Not Dare To Dream: Cyclic (Alkyl)(amino)carbenes (cAACs) as New Key Players in Transition‐Metal Chemistry

The first synthesis of cyclic (alkyl)(amino)carbenes (cAACs) was reported in 2005, and since then this class of carbenes has been on a victory tour in main‐group‐element and transition‐metal chemistry. CAACs are easy to synthesize and among the most nucleophilic (σ‐donating) and simultaneously most electrophilic (π‐accepting) carbenes known to date. These properties have led to a vast number of applications of cAACs in main‐group‐element chemistry in, for example, the activation of small‐molecule compounds and enthalpically strong bonds, as well as in the stabilization of highly reactive main‐group‐element compounds. They also proved to possess outstanding ligand properties in transition‐metal chemistry in, for example, the stabilization of unusual low‐valent transition‐metal complexes, leading to enormously highly active but robust catalysts. Here a brief overview of cAAC‐ligated transition‐metal compounds, mainly in low oxidation states, with an emphasis on nickel complexes, is provided, and a personal account of some of the recent developments in the use of cAACs in coordination chemistry and catalysis is given.