Unlike catalyst 7, catalyst 11 was found to have a weaker fumarate binding energy that was 4.2 kcal/mol uphill of catalyst 1. The inactivity of 11, despite having the same fumarate as activate catalyst 7, indicated that catalyst activity is not solely dependent on fumarate identity, but may also be affected by the interplay between the NHC ligand and the fumarate ligand.