Cyclic (alkyl)(amino)carbenes (CAACs) are both stronger σ-donors and π-acceptors than traditional N-heterocyclic carbenes (NHCs). These enhanced electronics have allowed for the activation of small molecules (NH3, H2, CO, P4, etc.), as well as for the stabilization and isolation of main-group, organic and low-valent transition-metal radicals. Furthermore, due to their ability to make strong carbon-metal bonds, CAACs have also shown drastically improved ruthenium, gold and copper catalysis. Although the chemistry of CAACs is vast, it has so far been limited to only 5-membered ring carbenes. Additionally, due to synthetic restrictions, the nitrogen heteroatom has always carried a phenyl derivative as a substituent. Using a new synthetic approach, we can now not only generate 6-membered ring CAACs, but we can also install a wide range of sterically varying alkyl groups on the nitrogen atom. The replacement of the phenyl substituent with an alkyl group greatly enhances the overall donor properties of these new CAACs. 6-membered CAACs are stable below -60 oC and can be bound in situ to many transition-metals. In this presentation, we will discuss the synthesis and electronic properties of these new carbenes as well as their use in coordination chemistry and catalysis.

6-membered Cyclic (alkyl)(amino)carbenes as strong donor ligands for transition-metals in catalysis

251st National Meeting (2016)

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