The [Fe{(SePPh2)2N}2] Complex Revisited: X‐ray Crystallography, Magnetometry, High‐Frequency EPR, and Mössbauer Studies Reveal Its Tetrahedral FeIISe4 Coordination Sphere

The synthesis and characterization of complex [Fe{(SePPh2)2N}2] (1) is described. X‐ray crystallography shows that this system contains a tetrahedral FeSe4 coordination sphere. The structural features of 1 are compared with those of similar first row transition element complexes, including a recently reported preparation of [Fe{(SePPh2)2N}2] (1SP) exhibiting a highly unusual square planar FeSe4 coordination sphere. The electronic structure of 1 was elucidated by magnetometry, high‐frequency EPR, and Mössbauer spectroscopic studies, which reveal zero‐field splitting (ZFS) parameters typical of high spin S = 2 tetrahedral FeII sites. Accurate ZFS parameters (D = +8.22 cm–1, E/D = 0.104) were obtained by analysis of the EPR spectra and compared with those of the analogous [Fe{(SPPh2)2N}2] complex. The literature complex [Fe{(SePPh2)2N}2] was re‐investigated by X‐ray crystallography, magnetometry, high frequency EPR and Mössbauer spectroscopy, revealing its tetrahedral FeSe4 coordination sphere and determining its spin Hamiltonian parameters.