| NHC | N-heterocyclic carbene |
| I | imidazol-2-ylidene |
| IR | R-substituted imidazol-2-ylidene |
| Me | methyl group |
| Pr | isopropyl group |
| Bu | tert-butyl group |
| Ph | phenyl group |
| Mes | mesityl group |
| Dipp | 2,6-diisopropylphenyl group |
| Ad | adamantyl group |
| QTAIM | quantum theory of atoms in molecules |