Table 3.
Absolute energies and electron populations of ligand natural orbitals important for the Ti-NHC interaction.

| Orbital a | MaH2 b | MbH2 | McH2 | ||
|---|---|---|---|---|---|
| C σ |
|
Population (№ of electrons) | 1.71 | 1.74 | 1.69 |
| Energy (kcal mol−1) | −136.2 | −142.0 | −133.3 | ||
| C-N π |
|
Population (№ of electrons) | 1.85 | 1.86 | 1.90 |
| Energy (kcal mol−1) | −200.4 | −200.3 | −198.3 | ||
| C-N π* |
|
Population (№ of electrons) | 0.49 | 0.45 | 0.42 |
| Energy (kcal mol−1) | −37.4 | −37.4 | −33.9 | ||
a The backbone of the NHC shown in the orbital figures is unsaturated for MaH2, benzannulated for MbH2 and saturated for McH2, see Scheme S1. b MaH2, MbH2 and McH2 are the neutral, model, OH-containing free-carbene ligands of the complexes 1a, 1b-THF and 1c.