The energetic preference of the FeNP + isomer vs the FePN + is surprising because we initially expected a better orbital overlap between iron and phosphorus and a preference of the FePN + isomer. However, our local energy decomposition (LED) and natural orbital chemical valence (NOVC) analysis indicates that the interaction between the ligand and the metal center is of significant covalent nature (see Figure top for intrinsic bond orbitals (IBOs) and Figure -S30 and Table -S11). In the NOCV/EDA analysis of FeNP + we obtain an energy of -90.8 kcal mol -1 (Table ) for the orbital interaction term ∆Eorb, representing orbital mixing effects, e.g., charge transfer and polarization effects. As the term is similar for FePN + (-98.8 kcal mol -1 ), this is indicative that the interaction between the ligand and the metal center is strongly covalent in nature and mainly dominated by the ∆Esteric term (44.0 kcal mol -1 for FeNP + and 66.8 kcal mol -1 for FePN + ). The most important mixing contributions for FeNP + is the π-backdonation from the occupied d orbitals of suitable symmetry on the Fe atom to the empty LUMO antibonding π* orbitals of the ligand ∆Eorb[d(Fe) → π*(NP)] (-28.6 kcal mol -1 , Figure ) and ∆Eorb[d(Fe) → π⊥(NP)] (-21.9 kcal mol -1 , Figure ). Another significant contribution is the σ-donation from the HOMO of the ligand to the empty d orbitals of Fe ∆Eorb[σ(NP) → d(Fe)] (-32.1 kcal mol -1 , Figure ). The relative stability of the isomers correlates well only with Pauli repulsion effects. Thus, the relative stability between the isomers essentially originates from the fact that the atomic orbitals on phosphorus are larger and more diffuse than those on nitrogen. This causes an increase in Pauli repulsion when the ligand coordinates from the phosphorus side. This is not compensated by a corresponding increase in orbital interactions, as quantified by the NOCV scheme (Table ). With a dinitrogen ligand in FeN2 + the orbital interactions are qualitatively the same as in FeNP + . In general, the frontier orbitals of N2 are of similar shape and nature as in PN (Figure ). However, the LUMO orbitals of N2 feature higher energies than those of PN, whilst the HOMO and HOMO-1 orbitals show lower energies. Hence, N2 is expected to be a poorer π acceptor as well as a poorer σ donor than PN. This is confirmed by our NOCV/EDA analysis. All donation and back donation components are smaller in ). The covalent interaction between the iron center and the PN ligand is also shown by IBO analysis (Figure top). The backbonding of the metal to the ligand is only minimal (see second row right orbital in Figure ) and in stark contrast to the situation for [Mo](PN) -complex reported by the Smith group (Figure ). In summary, we presented the synthesis and development of a molecular precursor N3PA that dissociates at room temperature and slowly releases dinitrogen, anthracene and phosphorus mononitride with a half-life of roughly half an hour. Phosphorus mononitride polymerizes very rapidly in solution by forming yellow-orange-brown polymers but can be efficiently transferred and trapped as demonstrated by the synthesis of [(dppe)Fe(Cp*)(NP)][BArF24]. The PN ligand is surprisingly N-bonded to the iron center because of a significant covalent iron pnictogen bond character that results in less Pauli repulsion when the ligand coordinates from the N side. The synthesis of N3PA and the prepared iron complex with a PN ligand opens new pathways to conduct further reactivity studies of the PN molecule in the future.