Inorganic Ferrocene Analogue [Fe(P4)2]2-

Inorganic metallocene derivatives containing only cyclo-P-n ligands have been targeted for more than 20 years, but their syntheses have never been achieved by pursuing the conventional route of using P-4 phosphorus except for the generation of [Ti(eta(5)-P-5)(2)](2-). Herein, we report a facile one-step method for the synthesis of the homoleptic iron complex [Fe(P-4)(2)](2-) by the Zintl-phase-type precursor KP. P-31 NMR analyses indicate that upon dissolving the KP phase in ethylenediamine P-4(2-) 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(P-4)(2)](2-). Both the FeII and the FeIII precursors can oxidize P-4(2-) to give a concomitant product [(P-7)Fe(P-4)](3-), which can be partially inhibited by the addition of potassium to produce relatively pure crystalline [K(2,2,2-crypt)](2)[Fe(P-4)(2)].