By reacting Fe(CO) _5 and SnI _4 in the ionic liquids [XIm][NTf _2] (XIm: 1-ethyl-3-methylimidazolium/EMIm, 1-ethyl-imidazolium/EHIm, 1-propyl-3-methylimidazolium/PMIm; NTf 2: bistrifluoridomethansulfonimide), the compounds [XIm][FeI(CO) _3(SnI _3) _2] are obtained as transparent, dark red crystals. According to single-crystal structure analysis, the title compounds crystallize monoclinically and contain the anionic carbonyl complex [FeI(CO) _3(SnI _3) _2] ~- as well as [EMIm] ~+, [EHIm] ~+ or [PMIm] ~+ cations. The anionic carbonyl is composed of a Sn-Fe-Sn barbell-shaped building unit with Fe-Sn distances of 252.0(1) pm. Herein, tin is coordinated distorted tetrahedrally by iodine; iron is coordinated pseudo-octahedrally by three carbonyl ligands, one iodine atom and two tin atoms. Bonding situation and valence state are investigated in detail for [EMIm][FeI(CO) _3(SnI _3) _2] based on bond-lengths considerations, infrared spectroscopy, M?ssbauer spectroscopy, density functional theory and DFT-based Mulliken population analysis. Hence, the formal oxidation state of the metal atoms can be concluded to Fe ~(±0) and Sn ~(3+).
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