Table 1.
Comparison of the geometric parameters, rotational barrier about the CringN bonds, and spectroscopic data for compounds 2, 3 and 4.
| Compound | Cring-N Bond Lengtha (Å) |
Carbene Angle (°) |
Rotational Barrierb (kJ/mol) |
13C NMRc (ppm) |
|---|---|---|---|---|
| 2[10] | 1.306 | 62.3 | 75 | 99 |
| 3 | 1.328 | 59.1 | 56 | 167 |
| 4[10] | 1.334 | 57.2 | 53 | 185 |
a
: average value of the CringN bond lengths.
b
: Calculated based on variable temperature NMR experiments.
c
: Chemical shift for the carbene carbon and the corresponding carbon in 2 and 3.