Investigating the Structural, Spectroscopic, and Electrochemical Properties of [Fe{(EP i Pr₂)₂N}₂] (E = S, Se) and the Formation of Iron Selenides by Chemical Vapor Deposition

The anionic L = [(EPiPr ₂ ) ₂ N] ^– (E = S, Se) form of the dichalcogenidoimidodiphosphinato-type ligands containing iPr peripheral groups has been shown previously to afford tetrahedral [M ^II L ₂ ] complexes (E = S, M = Mn, Co, Ni, Zn; E = Se, M = Co, Ni, Zn). The syntheses of the analogous [FeL ₂ ] complexes [E = S (1), Se (2)] were performed in this work through metathesis reactions between FeCl ₂ and the corresponding KL salts. For both 1 and 2, X-ray crystallography revealed two distinct molecules in the asymmetric unit. Complexes 1 and 2 are isostructural and exhibit P–E and P–N bond-length differences compared with those of the free ligands, and these differences are translated into shifts of the corresponding IR bands. Cyclic voltammetry studies showed that the Fe ^II → Fe ^III oxidation in 2 occurs at a lower potential than that of 1. The zero-field Mössbauer spectra of the two complexes are quite similar and provide evidence of similar S = 2 electronic structures. The observation of crystallographically distinct Fe ^II E ₄ sites for both 1 and 2 is also revealed in the corresponding Mössbauer spectra. Complex 2 was employed as a single-source precursor in catalyst-aided chemical vapor deposition experiments, which afforded the iron selenides FeSe and Fe ₃ Se ₄ .