Table 4.
Experimental T 1 values, determined at 9.4 T in methanol‐d 4 solution for the indicated proton nuclei of free and bound imidazole (5b) at 263 and 298 K respectively
| Temperature | 263 K | 298 K | 298 K (with HCl) | ||||
|---|---|---|---|---|---|---|---|
| Catalyst | Proton/T 1 (s) | IMes | d 22‐IMes | IMes | d 22‐IMes | IMes | d 22‐IMes |
| Free substrates | H‐2 | 33.7 | 25.5 | 16.9 | 22.9 | 15.8 | 21.8 |
| H‐4 and H‐5 | 14.1 | 12.0 | 12.2 | 15.1 | 11.9 | 14.8 | |
| NCMe | 8.2 | 9.6 | 8.3 | 9.5 | 7.9 | 10.3 | |
| Bound imidazole | H‐2eq | 3.1 | 4.3 | 13.7 | 14.1 | 8.7 | 13.4 |
| H‐4eq | 1.6 | 2.4 | 13.6 | 17.4 | 11.2 | 17.8 | |
| H‐5eq | 1.0 | 1.2 | 9.3 | 9.4 | 3.2 | 6.6 | |
| H‐2ax | 4.1 | 3.1 | 4.0 | 3.0 | 4.4 | 7.6 | |
| H‐4ax | 2.7 | 3.6 | 7.9 | 3.5 | 9.5 | 7.1 | |
| H‐5ax | 2.8 | 1.7 | 4.6 | 2.5 | 5.5 | 4.9 | |
| Temperature | 263 K | 298 K | 298 K (with HCl) | ||||
| Catalyst | Proton/T 1 (s) | SIMes | d 22‐SIMes | SIMes | d 22‐SIMes | SIMes | d 22‐SIMes |
| Free substrates | H‐2 | 34.4 | 25.9 | 17.0 | 14.8 | 13.2 | 12.8 |
| H‐4 and H‐5 | 14.7 | 13.0 | 12.8 | 14.0 | 10.5 | 12.1 | |
| NCMe | 11.5 | 10.8 | 9.8 | 14.7 | 8.2 | 14.3 | |
| Bound imidazole (eq = equatorial) (ax = axial) | H‐2eq | 3.5 | 3.7 | 13.0 | 11.0 | 13.1 | 9.9 |
| H‐4eq | 1.8 | 1.4 | 11.1 | 10.0 | 11.0 | 10.2 | |
| H‐5eq | 1.9 | 1.9 | 9.7 | 8.8 | 10.6 | 10.5 | |
| H‐2ax | — | 3.0 | — | 8.2 | — | — | |
| H‐4ax | 2.8 | 3.6 | 7.9 | 6.0 | 17.9 | 7.5 | |
| H‐5ax | — | 2.6 | 4.2 | 3.8 | 13.8 | 4.8 | |
The associated reagent concentrations were 6.5 mM (iridium), 65 mM (imidazole) and 19.5 mM (acetonitrile), and the labelling follows that in Scheme 1.