Inorganic metallocene derivatives containing only cyclo-Pn ligands have been targeted for more than 20 years, but their syntheses have never been achieved by pursuing the conventional route of using P4 phosphorus except for the generation of [Ti(η5-P5)2]2-. Herein, we report a facile one-step method for the synthesis of the homoleptic iron complex [Fe(P4)2]2- by the Zintl-phase-type precursor KP. 31P NMR analyses indicate that upon dissolving the KP phase in ethylenediamine P42- was generated only in the presence of 2,2,2-crypt. The amounts of cation-sequestering agents, the type of iron precursor, and their consuming ratio have a decisive impact on the yield of [Fe(P4)2]2-. Both the FeII and the FeIII precursors can oxidize P42- to give a concomitant product [(P7)Fe(P4)]3-, which can be partially inhibited by the addition of potassium to produce relatively pure crystalline [K(2,2,2-crypt)]2[Fe(P4)2].