We explored the potential energy surface around FeNP computationally. As a global energetic minimum we located a closed shell (S = 0, with S as the total spin number of the system) low spin electronic ground state for the [(dppe)Fe(Cp*)(NP)] + cation (FeNP + ) at the DLPNO-CCSD(T)/cc-pVTZ//PBE0-D3(BJ)/cc-pVTZ + thermal correction to Gibbs free energy level of theory (Figure ). Isomerization of the NP ligand occurs via the side-on bound isomer that is connected via TS1 (25.5 kcal mol -1 , Figure ) to FeNP + and 16.8 kcal mol -1 energetically less preferred. Further isomerization via TS2 (36.6 kcal mol -1 , Figure ) leads to the PN linkage isomer FePN + that is surprisingly 14.3 kcal mol -1 higher in energy than the FeNP + isomer. We computed the 31 P NMR chemical shifts of all three isomers according to a literature benchmark study at the PBE0-D3(BJ)/6-31G(d) level of theory. According to the computations all three isomers should be distinguishable by NMR spectroscopy as they are separated by roughly 80 ppm (Figure ). The computed chemical shift for FeNP + with δ 282 ppm is in good agreement with the experimentally observed resonance at δ 271 ppm. The energetic high barrier of TS2 (36.6 kcal mol -1 ) prevents isomerization of the NP ligand at room temperature. Even after refluxing the complex in toluene or after irradiation with green and yellow light with light emitting diodes (LEDs) we did not observe any new resonance by P NMR spectroscopy.