Table 1. 15N NMR Chemical and Coordination Shiftsa (ppm) of the Halogen(I), Silver(I), and Proton Complexes of Pyridine15,19,62,63.
| entry | structure | δ(15N) | δ(15N)coord |
|---|---|---|---|
| 1 | pyridine (Pyr) | –67.0 | |
| 2 | PyrH+BF4– | –186.5 | –119.5 |
| 3 | (Pyr)2H+BF4– | –134.1 | –67.1 |
| 4 | (Pyr)2Ag+BF4– | –126.5 | –59.5 |
| 5 | (Pyr)2I+BF4– | –175.1 | –108.1 |
| 6 | (Pyr)2Br+BF4– | –142.9 | –75.9 |
| 7 | (Pyr)2Cl+BF4– | nac | nac |
| 8 | (Pyr)2F+BF4– | –122.1 /–68.8b | –55.1/–1.8 |
| 9 | (4-NMe2-Pyr)2I+BF4– | –214.2 | –104.8 |
| 10 | (4-CF3-Pyr)2I+BF4– | –164.1 | –112.5 |
a
The 15N NMR coordination shift represents the chemical shift change upon complex formation, δ(15N)coord = δ(15N)complex – δ(15N)ligand.
b
Measured in CDCN3 at −35 °C; all other chemical shifts given here were measured in CD2Cl2. The fluorine(I) complex is asymmetric, and accordingly, its nitrogens have different chemical shifts.