Is the Corrolate Macrocycle Innocent or Noninnocent? Magnetic Susceptibility, Mössbauer, 1H NMR, and DFT Investigations of Chloro- and Phenyliron Corrolates
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- 作者：Olga Zakharieva ; Volker Schü ; nemann ; Michael Gerdan ; Silvia Licoccia ; Sheng Cai ; F. Ann Walker ; and Alfred X. Trautwein
- 刊名：Journal of the American Chemical Society
- 出版年：2002
- 出版时间：June 12, 2002
- 年：2002
- 卷：124
- 期：23
- 页码：6636 - 6648
- 全文大小：238K
- 年卷期：v.124,no.23(June 12, 2002)
- ISSN：1520-5126
文摘
In an attempt to determine the electron configuration of (anion)iron corrolates, i.e., whether theyare S = 1 Fe(IV)-corrolate(3-) or S = 3/2 Fe(III)-corrolate(2-
), with antiferromagnetic coupling between theiron and macrocycle electrons to yield overall S = 1, two axial ligand complexes of an iron octaalkylcorrolatehave been studied by temperature-dependent magnetic susceptibility, magnetic Mössbauer, and 1H NMRspectroscopy, and the results have been compared to those determined on the basis of spin-unrestrictedDFT calculations. Magnetic susceptibility measurements indicate the presence of a noninnocent macrocycle(corrolate (2-)) for the chloroiron corrolate, with strong antiferromagnetic coupling to the S = 3/2 Fe(III)center, while those for the phenyliron corrolate are not conclusive as to the electron configuration.Temperature- and field-dependent Mössbauer spectroscopic investigations of these two complexes yieldedspectra that could be simulated with either electron configuration, except that the isomer shift of the phenyl-iron complex is -0.10 mm/s while that of the chloroiron complex is +0.21 mm/s, suggesting that the ironin the former is Fe(IV) while in the latter it is Fe(III). 1H NMR spectroscopic studies of both axial ligandcomplexes show large negative spin density at the meso carbons, with those of the chloroiron complex(Cai, S.; Walker, F. A.; Licoccia, S. Inorg. Chem. 2000, 39, 3466) being roughly four times larger thanthose of the phenyliron complex. The temperature dependence of the proton chemical shifts of the phenylironcomplex is strictly linear. DFT calculations are consistent with the chloroiron complex being formulated asS1 = 3/2 Fe(III)-corrolate (2-) S2 = 1/2, with negative spin density at all nitrogens and meso carbons, anda net spin density of -0.79 on the corrolate ring and positive spin density (+0.17) on the chloride ion and+2.58 on the iron. In contrast, the phenyliron complex is best formulated as S = 1 Fe(IV)-corrolate (3-),but again with negative spin density at all nitrogens and meso carbons of the macrocycle, yet with the netspin density on the corrolate ring being virtually zero; the phenyl carbanion carbon has relatively largenegative spin density of -0.15 and the iron +2.05. On the basis of all of the results, we conclude that inboth the chloroiron and phenyliron complexes the corrolate ring is noninnocent, in the chloroiron complexto a much larger extent than in the phenyliron complex.
), with antiferromagnetic coupling between theiron and macrocycle electrons to yield overall S = 1, two axial ligand complexes of an iron octaalkylcorrolatehave been studied by temperature-dependent magnetic susceptibility, magnetic Mössbauer, and 1H NMRspectroscopy, and the results have been compared to those determined on the basis of spin-unrestrictedDFT calculations. Magnetic susceptibility measurements indicate the presence of a noninnocent macrocycle(corrolate (2-)) for the chloroiron corrolate, with strong antiferromagnetic coupling to the S = 3/2 Fe(III)center, while those for the phenyliron corrolate are not conclusive as to the electron configuration.Temperature- and field-dependent Mössbauer spectroscopic investigations of these two complexes yieldedspectra that could be simulated with either electron configuration, except that the isomer shift of the phenyl-iron complex is -0.10 mm/s while that of the chloroiron complex is +0.21 mm/s, suggesting that the ironin the former is Fe(IV) while in the latter it is Fe(III). 1H NMR spectroscopic studies of both axial ligandcomplexes show large negative spin density at the meso carbons, with those of the chloroiron complex(Cai, S.; Walker, F. A.; Licoccia, S. Inorg. Chem. 2000, 39, 3466) being roughly four times larger thanthose of the phenyliron complex. The temperature dependence of the proton chemical shifts of the phenylironcomplex is strictly linear. DFT calculations are consistent with the chloroiron complex being formulated asS1 = 3/2 Fe(III)-corrolate (2-) S2 = 1/2, with negative spin density at all nitrogens and meso carbons, anda net spin density of -0.79 on the corrolate ring and positive spin density (+0.17) on the chloride ion and+2.58 on the iron. In contrast, the phenyliron complex is best formulated as S = 1 Fe(IV)-corrolate (3-),but again with negative spin density at all nitrogens and meso carbons of the macrocycle, yet with the netspin density on the corrolate ring being virtually zero; the phenyl carbanion carbon has relatively largenegative spin density of -0.15 and the iron +2.05. On the basis of all of the results, we conclude that inboth the chloroiron and phenyliron complexes the corrolate ring is noninnocent, in the chloroiron complexto a much larger extent than in the phenyliron complex.