The diamagnetic nature of the two prepared transition metal complexes allowed us further spectroscopic characterization by multinuclear NMR spectroscopy. The singlet signal at δ 85 ppm in the 31 P{ 1 H} spectrum of the dppe ligand in FeN2 (Figure ) is split into a doublet in FeNP and slightly shifted downfield to δ 86 ppm (Figure ). In addition, a triplet resonance is observed for the NP ligand at δ 271 ppm with a coupling constant of 3 JPP = 9.2 Hz. We synthesized 50% enriched Fe 14/15 NP by treatment of FeN2 with 15 N labeled 15 N3PA (vide supra). In the ~50% N isotopically enriched Fe 14/15 NP complex the triplet resonance at at δ 271 ppm splits into a doublet of triplets, partially overlapping with the unlabeled triplet (Figure ). A weak doublet at δ 450 pm ( 1 JNP = 51.1 Hz) is observed in the N NMR spectrum (Figure ). Our attempts to determine the 31 P-57 Fe coupling constant between the PN ligand and the iron center failed. We were only able to determine the coupling constant of the dppe ligand to the 57 Fe center to be 1 JFeP = 55. 4 Hz in FeN2 (Figure ) and 1 JFeP = 56.5 Hz in FeNP (Figure ).