Tuning the π-Accepting Properties of Mesoionic Carbenes: A Combined Computational and Experimental Study

Mesoionic imidazolylidenes are recognized as excellent electron-donating ligands in organometallic and main group chemistry. However, these carbene ligands typically show poor pi-accepting properties. A computational analysis of 71 mesoionic imidazolylidenes that bear different aryl or heteroaryl substituents in C2 position was performed. The study has revealed that a diphenyltriazinyl (Dpt) substituent renders the corresponding carbene particularly pi-acidic. The computational results could be corroborated experimentally. A mesoionic imidazolylidene with a Dpt substituent was found to be a better sigma-donor and a better pi-acceptor compared to an Arduengo-type N-heterocyclic carbene. To demonstrate the utility of the new carbene, the ligand was used to stabilize a low-valent paramagnetic tin compound.

Automated summary

The study found that mesoionic imidazolylidenes bearing a diphenyltriazinyl (Dpt) substituent exhibit improved pi-acidic properties compared to Arduengo-type N-heterocyclic carbenes. This discovery was supported by computational analysis and experimental evidence. The new carbene was utilized to stabilize a low-valent paramagnetic tin compound, demonstrating its usefulness.