Non-innocent Intercalation of Diamines into Tetragonal FeS Superconductor

We report two solvothermal pathways toward intercalated iron sulfide, [Fe8S10]Fe(en)(3)center dot en(0.5) (en = ethylenediamine), featuring [Fe8S11](2-) layers stacked by [Fe(en)(3)](2+) cations and free ethylenediamine molecules. [Fe8S10]Fe(en)(3)center dot en(0.5) is synthesized in a simple single-step method from Fe and S in ethylenediamine with addition of NH4Cl mineralizer as well as from solvothermal treatment of mackinawite, tetragonal FeS. In situ synchrotron powder X-ray diffraction experiments reveal a clear transformation of tetragonal FeS into [Fe8S10]Fe(en)(3)center dot en(0.5) upon reaction with ethylenediamine. In-house control synthetic experiments confirmed the chemical process, whereby ethylenediamine leaches iron solely from the tetragonal Fe-S layers to form [Fe(en)(3)](2+) complexes and thereby oxidize the intralayer iron to Fe2.25+. Our report emphasizes that, in layered iron chalcogenides, diamines can intercalate as charged coordination complexes in tandem with neutral diamine molecules.

Automated summary

Two solvothermal pathways were reported for the preparation of intercalated iron sulfide [Fe8S10]Fe(en)(3)·en(0.5), showing that diamines can intercalate as charged coordination complexes in layered iron chalcogenides along with neutral diamine molecules.