Extending the comparison to the entire set of 124 structures shown in Figure significantly degrades the correlation (R 2 = 0.64). However, it is noteworthy that the structures most divergent from imidazol-2-ylidenes, such as diaminocyclopropenylidene (122, class S), carbodicarbenes (2-4, class U), or carbodiphosphoranes (1 and 6, class T), exhibit the largest deviations from the correlation line obtained for classes A-I. Limiting the comparison to structures containing at least one nitrogen atom directly bonded to the carbenic carbon (i.e., mono-and diaminocarbenes classes A-Q), whether cyclic or acyclic, results in an imperfect but acceptable correlation (R² = 0.84). It should be noted, however, that this agreement is only achieved by excluding certain outliers, namely the three class A Clsubstituted carbenes and the three class K acyclic (aryl)amino carbenes 7, 8 and 20