A simply accessible organometallic system to gauge electronic properties of N-heterocyclic carbenes

The intricate sigma and pi-bonding of N-heterocyclic carbenes (NHCs) to metals and the need to quantify their electronic properties to rationalize reactivity of complexes have resulted in the creation of numerous methodologies to understand the NHC-metal interaction which are, as we now show, flawed. Our search for a unified, easily accessible system to gauge these fundamental properties has resulted in the discovery of two systems that highlight the flaws present in existing systems and provide a more accurate measure of the NHC ligand electronic properties. Two new model complexes function as electrochemical probes for the evaluation of electronic properties of N-heterocyclic carbene ligands. The linear ones unearth flaws of previous probes when evaluating the most sterically demanding NHCs.