We computed the most essential part of the potential energy surface around N3PA at PBE0-D3(BJ)/cc-pVTZ + Gibbs free energy correction with augmented DLPNO-CCSD(T)/cc-pVTZ single point energies (Figure ). We located two minima for N3PA, and the energetically preferred conformer is in line with our crystal structure depicted in Figure . In the higher energy conformer the P-N single bond is rotated by 180° and the azide group takes a parallel position to a terminal aromatic ring that results in an energy rise of 0.9 kcal mol -1 . Both conformers are connected by a low lying transition state TS3 (2.9 kcal mol -1 ). For the decomposition of N3PA, two fragmentation pathways have been considered, first: cleavage of dinitrogen from the azide group and the formation of phosphinonitrene NPA (TS4 23.3 kcal mol -1 and TS5 39.8 kcal mol -1 ) that easily further dissociates into N2, PN and A via TS6 (1.7 kcal mol -1 ). The second pathway is connected with the cleavage of anthracene. In an initial step a phosphirane intermediate (I1) forms via TS2 (33.9 kcal mol -1 ) that further dissociates into N2, PN and A via TS1 (42.5 kcal mol -1 ). Based on the computed free energy values the first pathway with an initial cleavage of dinitrogen is energetically favored. The minimum energy decomposition pathway with a total barrier of 23.3 kcal mol -1 is within the experimental error of our Eyring analysis (ΔG ⧧ = ΔH ⧧ -TΔS ⧧ = 22.1 ± 1.5 kcal mol -1 at 298.15 K). Next we focused on the ability of N3PA to transfer a PN molecule as a ligand to a transition metal complex. As indicated by our computations (vide supra) the N3PA molecule has two reactive sites. The reaction may be initiated by cleavage of the azide unit in a Staudinger-type reaction with dinitrogen release and the remaining NPA unit might be transferred to a transition metal. On the other hand the Cummins group has already demonstrated phosphinidene transfer reactivity of various RPA compounds (including R = Me2N, Et2N, Me2Pip, i Pr2N). Inspired by the recent work of Hamon et al. we synthesized [(dppe)Fe(Cp*)(N2)][BArF24] (FeN2, dppe = 1,2-bis(diphenylphosphino)ethane, Cp* = 1,2,3, 4,5-pentamethylcyclopentadienyl, BArF24 = Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) by treatment of (dppe)Fe(Cp*)(Cl) with NaBArF24. After stirring the latter two reagents for 60 min in diethyl ether, the initially dark brown solution turned red and a colorless precipitate (NaCl) developed. After filtration through Celite and layering the filtrate with pentane, dark red crystalline blocks formed after one day (Figure ). FeN2 was characterized by IR, NMR, and Mößbauer spectroscopy as well as single crystal X-ray crystallography (vide infra, Figure , S7-S11, S25 and Table ). We found a nitrogen-nitrogen bond length of 1.131(7) Å within the single crystal that is only slightly longer than the dinitrogen triple bond in the gas phase (1.09768(5) Å). Treatment of FeN2 with an excess of N3PA (~3 equiv.) at room temperature in diethyl ether immediately led to a gas evolution and precipitation of anthracene as a colorless solid. After filtration the filtrate was placed in the freezer to crystallize further A that was removed by filtration. The filtrate was layered with pentane. After one day at room temperature dark red crystalline blocks (Figure ) were observed that were analyzed by IR, NMR, and Mößbauer spectroscopy as well as single crystal X-ray crystallography (vide infra, Figure , S13-S17, S26 and Table ). Our X-ray crystallographic study revealed the successful formation of [(dppe)Fe(Cp*)(NP)][BArF24] (FeNP) with the previously weak N2 ligand replaced by PN (Figure ). Surprisingly, the PN ligand is terminally N-bonded to the iron center and displays a PN bond length of 1.493(2) Å that is only slightly longer than in free gaseous PN (1.49086(2) Å, vide supra). This is indicative of a weak interaction between the ligand and the metal as also demonstrated in our theoretical analysis (vide infra). Intrinsic bond orbital (IBO) analysis reveals a Wiberg bond order of 2.51 for the PN ligand, which is minimally perturbed vis-a-vis the free PN molecule. The P-N bond distance in FeNP is longer than in in crystalline [Mes*NP] + salts (Mes* = 2,4,6-t Bu3C6H2), e.g., 1.475(8) Å in 1 or 1.467(4) in [Mes*NP][OTf] (OTf = CF3SO3 -). In comparison to [Mo](PN) -the PN distance is approximately 0.043 Å shorter. The Wiberg bond order for PN in [Mo](PN) -is 2.13. IBO charges reveal an almost neutral PN ligand in FeNP (N: -0.57, P: 0.57) in stark contrast to [Mo](PN) -where the PN ligand carries an overall significant negative charge (N: -0.95, P: 0.57). This is consistent with the latter system having considerably more back-bonding to the PN ligand (c.f. Figure and).