Table 1.

¹⁵N NMR shifts in ppm. The spectra are recorded in d₆ ‐DMSO, unless noted otherwise. All shifts are reported relative to an external nitromethane standard. Coordination shifts Δδ¹⁵N, if obtained, are given in squared brackets. ¹H‐¹⁵N HMBC spectra of complexes 1–6 and their ligands are given in the SI.

Compound	δ15Nimine [Δδ15Nimine]	δ15Npyridine [Δδ15Npyridine]	δ15NIM [Δδ15NIM]	δ15NAZ [Δδ15NAZ]
1	−83.2 [−13.7]		−173.4 [−57.3]	−203.7 [+7.1]
2	−86.0 [−16.1]		−171.7 [−55.2]	−205.6
3‐M	−89.6 [−41.7]	−128.6 [−67.0]
3‐D	−107.7 [−59.8]	−105.3 [−43.7]
4	−94.0 [−46.1]	−126.8 [−64.3]
5 [a]	−79.1		−170.5	−211.4
6	−86.1 [−21.1]		−170.0 [−52.8]	−206.1 [+3.5]

[a] measured in acetonitrile.