Hexakis(carbonyl)iron(II) Undecafluorodiantimonate(V), [Fe(CO)6][Sb2F11]2, and -Hexafluoroantimonate(V), [Fe(CO)6][SbF6]2,
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- 作者：Eduard Bernhardt ; Bianca Bley ; Rudolf Wartchow ; Helge Willner ; Eckhard Bill ; Peter Kuhn ; Iona H. T. Sham ; Matthias Bodenbinder ; Raimund Brö ; chler ; and Friedhelm Aubke
- 刊名：Journal of the American Chemical Society
- 出版年：1999
- 出版时间：August 11, 1999
- 年：1999
- 卷：121
- 期：31
- 页码：7188 - 7200
- 全文大小：175K
- 年卷期：v.121,no.31(August 11, 1999)
- ISSN：1520-5126
文摘
Hexakis(carbonyl)iron(II) undecafluorodiantimonate(V), [Fe(CO)6][Sb2F11]2, is conveniently preparedby the oxidative carbonylation of Fe(CO)5 with XeF2 as external oxidizer in the conjugate Br
nsted-Lewissuperacid HF-SbF5. The colorless compound crystallizes from the reaction medium in high purity. Themolecular structure is obtained by single-crystal X-ray diffraction. The cation is a regular octahedron, whilethe vertex-shared di-octahedral [Sb2F11]- anion is distorted from D4h symmetry by bending and rotationalprocesses, due to significant interionic interactions, primarily of the F···C type. Washing of [Fe(CO)6][Sb2F11]2with anhydrous HF results in an unusual elution of SbF5 and the quantitative conversion to hexakis(carbonyl)iron(II) hexafluoroantimonate(V) [Fe(CO)6][SbF6]2. The molecular structure of the salt shows octahedral ionswith slight tetragonal distortions for the cation (elongation) and the anion (compression). Both salts are thermallystable up to 150 
C. The averaged bond distances and the vibrational wavenumbers of [Fe(CO)6]2+ are nearlyidentical in both compounds. The [Fe(CO)6]2+ cation, the first and so far only isolated and structurallycharacterized dipositive, superelectrophilic carbonyl cation formed by a 3d-metal, is further characterized bya normal coordinate analysis (NCA). The obtained force constants are compared to those of the isoelectronicmolecule Cr(CO)6. Changes in 
-back-bonding affect the FCO/CO and FCO/MC interaction force constants morestrongly than the stretching force constants FCO and FMC. All 13 fundamentals of [Fe(CO)6]2+ are detectedand assigned with the help of the data obtained from the normal coordinate analysis and density functionalcalculations published previously. The electronic ground state 1A1g of the [Fe(CO)6]2+ cation is established bymagnetic susceptibility measurements of polycrystalline [Fe(CO)6][SbF6]2 and [Fe(CO)6][Sb2F11]2 between 2and 300 K. The magnetic impurity formed during synthesis is identified as Fe[SbF6]2 which has iron(II) inhigh spin (5T2g) ground state. Consistent with a diamagnetic ground state are the single line in the 57Fe Mössbauerspectrum (i.s. = -0.003(8) mm s-1 relative to 
-Fe), obtained on polycrystalline samples and the single sharpline in the 13C NMR spectrum in DF solution at 178 ppm with J (57Fe-13C) of 19.2 Hz.
nsted-Lewissuperacid HF-SbF5. The colorless compound crystallizes from the reaction medium in high purity. Themolecular structure is obtained by single-crystal X-ray diffraction. The cation is a regular octahedron, whilethe vertex-shared di-octahedral [Sb2F11]- anion is distorted from D4h symmetry by bending and rotationalprocesses, due to significant interionic interactions, primarily of the F···C type. Washing of [Fe(CO)6][Sb2F11]2with anhydrous HF results in an unusual elution of SbF5 and the quantitative conversion to hexakis(carbonyl)iron(II) hexafluoroantimonate(V) [Fe(CO)6][SbF6]2. The molecular structure of the salt shows octahedral ionswith slight tetragonal distortions for the cation (elongation) and the anion (compression). Both salts are thermallystable up to 150 C. The averaged bond distances and the vibrational wavenumbers of [Fe(CO)6]2+ are nearlyidentical in both compounds. The [Fe(CO)6]2+ cation, the first and so far only isolated and structurallycharacterized dipositive, superelectrophilic carbonyl cation formed by a 3d-metal, is further characterized bya normal coordinate analysis (NCA). The obtained force constants are compared to those of the isoelectronicmolecule Cr(CO)6. Changes in -back-bonding affect the FCO/CO and FCO/MC interaction force constants morestrongly than the stretching force constants FCO and FMC. All 13 fundamentals of [Fe(CO)6]2+ are detectedand assigned with the help of the data obtained from the normal coordinate analysis and density functionalcalculations published previously. The electronic ground state 1A1g of the [Fe(CO)6]2+ cation is established bymagnetic susceptibility measurements of polycrystalline [Fe(CO)6][SbF6]2 and [Fe(CO)6][Sb2F11]2 between 2and 300 K. The magnetic impurity formed during synthesis is identified as Fe[SbF6]2 which has iron(II) inhigh spin (5T2g) ground state. Consistent with a diamagnetic ground state are the single line in the 57Fe Mössbauerspectrum (i.s. = -0.003(8) mm s-1 relative to -Fe), obtained on polycrystalline samples and the single sharpline in the 13C NMR spectrum in DF solution at 178 ppm with J (57Fe-13C) of 19.2 Hz.