Begel S, Puchta R, Sutter J, Heinemann FW, Dahlenburg L, van Eldik R (2015)
Publication Language: English
Publication Status: Published
Publication Type: Journal article
Publication year: 2015
Publisher: American Chemical Society
Book Volume: 54
Pages Range: 6763-6775
DOI: 10.1021/acs.inorgchem.5b00595
In an earlier study we investigated the reaction of iron(II) chloride with NO in a strongly coordinating ionic liquid 1-ethyl-3-methylimidazolium dicyanamide [emim][dca] and showed that the actual reactive species in solution was [Fe-II(dca)(5)Cl](4-). For the present report we investigated in detail how this reaction could proceed in a noncoordinating ionic liquid 1-ethyl-3-methylimidazolium trifluoromethylsulfonate [emim][OTf]. The donor ability of OTf- is much lower than that of dca(-), such that the solubility of FeCl2 in [emim][OTf] strongly depended on other donors like water or chloride ions present or added to the ionic liquid. On increasing the chloride concentration in [emim] [OTf], the tetrachloridoferrate complex [emim](2)[FeCl4] was formed, as verified by X-ray crystallography. This complex undergoes reversible binding of NO, for which the UV-vis spectral characteristics of the green brown nitrosyl product resembled that found for the corresponding nitrosyl complexes formed in water and [emim][dca] as solvents. A detailed analysis of the spectra revealed that the {Fe-NO}(7) species has Fe-II-NO center dot character in contrast to Fe-III-NO- as found for the other solvents. The formation constant, however, is much higher than in [emim] [dca], lying closer to the value found for water as solvent. Surprisingly, the Mossbauer spectrum found in [emim][OTf] is very unusual and unsimilar to that found in water and [emim] [dca] as solvents, pointing at a different electron density distribution between Fe and NO in {Fe-NO}.(7) First, the high isomer shift points to the presence of iron(II) species in solution, thus indicating that upon NO binding no oxidation to iron(III) occurs. Second, the negligible quadrupole splitting suggests a high local symmetry around the iron center. The nitrosyl product is suggested to be [(FeCl3NO)-Cl-II](-), which is supported by electron paramagnetic resonance (EPR) and IR measurements. The nature of the Fe(II) complexes formed in [emim][OTf] depends on the additives required to dissolve FeCl2 in this ionic liquid.
APA:
Begel, S., Puchta, R., Sutter, J., Heinemann, F.W., Dahlenburg, L., & van Eldik, R. (2015). Studies on the Reaction of Iron(II) with NO in a Noncoordinating Ionic Liquid. Inorganic Chemistry, 54, 6763-6775. https://dx.doi.org/10.1021/acs.inorgchem.5b00595
MLA:
Begel, Svetlana, et al. "Studies on the Reaction of Iron(II) with NO in a Noncoordinating Ionic Liquid." Inorganic Chemistry 54 (2015): 6763-6775.
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