混合价态的[FeIV(μ-O)(μ-羧基)2FeIII]3+核心。

Mixed-valent [FeIV(mu-O)(mu-carboxylato)2FeIII]3+ core.

作者信息

Slep Leonardo D, Mijovilovich Ana, Meyer-Klaucke Wolfram, Weyhermüller Thomas, Bill Eckhard, Bothe Eberhard, Neese Frank, Wieghardt Karl

机构信息

Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany.

出版信息

J Am Chem Soc. 2003 Dec 17;125(50):15554-70. doi: 10.1021/ja030377f.

DOI:10.1021/ja030377f

PMID:14664603

Abstract

The symmetrically ligated complexes 1, 2, and 3 with a (mu-oxo)bis(mu-acetato)diferric core can be one-electron oxidized electrochemically or chemically with aminyl radical cations [*NR3][SbCl6] in acetonitrile yielding complexes which contain the mixed-valent [(mu-oxo)bis(mu-acetato)iron(IV)iron(III)]3+ core: ([9]aneN3)(2FeIII2)(mu-O)(mu-CH3CO2)22 (1(ClO4)2), (Me3[9]aneN3)(2FeIII2)(mu-O)(mu-CH3CO2)22 (2(PF6)(2)), and [(tpb)(2FeIII2)(mu-O)(mu-CH3CO2)2] (3) where ([9]aneN3) is the neutral triamine 1,4,7-triazacyclononane and (Me3[9]aneN3) is its tris-N-methylated derivative, and (tpb)(-) is the monoanion trispyrazolylborate. The asymmetrically ligated complex (Me3[9]aneN3)FeIII(mu-O)(mu-CH3CO2)2FeIII(tpb) (4(PF6)) and its one-electron oxidized form [4ox]2+ have also been prepared. Finally, the known heterodinuclear species (Me3[9]aneN3)CrIII(mu-O)(mu-CH3CO2)2Fe([9]aneN3)2 (5(PF6)(2)) can also be one-electron oxidized yielding [5ox]3+ containing an iron(IV) ion. The structure of 4(PF6).0.5CH3CN.0.25(C2H5)2O has been determined by X-ray crystallography and that of [5ox]2+ by Fe K-edge EXAFS-spectroscopy (Fe(IV)-O(oxo): 1.69(1) A; Fe(IV)-O(carboxylato) 1.93(3) A, Fe(IV)-N 2.00(2) A) contrasting the data for 5 (Fe(III)-O(oxo) 1.80 A; Fe(III)-O(carboxylato) 2.05 A, Fe-N 2.20 A). [5ox]2+ has an St = 1/2 ground state whereas all complexes containing the mixed-valent [FeIV(mu-O)(mu-CH3CO2)2FeIII]3+ core have an St = 3/2 ground state. Mössbauer spectra of the oxidized forms of complexes clearly show the presence of low spin FeIV ions (isomer shift approximately 0.02 mm s(-1), quadrupole splitting approximately 1.4 mm s(-1) at 80 K), whereas the high spin FeIII ion exhibits delta approximately 0.46 mm s(-1) and DeltaE(Q) approximately 0.5 mm s(-1). Mössbauer, EPR spectral and structural parameters have been calculated by density functional theoretical methods at the BP86 and B3LYP levels. The exchange coupling constant, J, for diiron complexes with the mixed-valent FeIV-FeIII core (H = -2J S1.S2; S(1) = 5/2; S2 = 1) has been calculated to be -88 cm(-1) (intramolecular antiferromagnetic coupling) and for the reduced diferric form of -75 cm(-1) in reasonable agreement with experiment (J = -120 cm(-1)).

摘要

具有（μ-氧代）双（μ-乙酸根）二铁核心的对称连接配合物1、2和3可以通过电化学方法或在乙腈中用氨基自由基阳离子[*NR3][SbCl6]进行化学单电子氧化，生成含有混合价态[(μ-氧代)双(μ-乙酸根)铁(IV)铁(III)]3+核心的配合物：([9]环壬三胺)(2FeIII2)(μ-O)(μ-CH3CO2)22 (1(ClO4)2)、(Me3[9]环壬三胺)(2FeIII2)(μ-O)(μ-CH3CO2)22 (2(PF6)2)和[(tpb)(2FeIII2)(μ-O)(μ-CH3CO2)2] (3)，其中([9]环壬三胺)是中性三胺1,4,7-三氮杂环壬烷，(Me3[9]环壬三胺)是其三-N-甲基化衍生物，(tpb)(-)是单阴离子三吡唑基硼酸根。还制备了不对称连接的配合物(Me3[9]环壬三胺)FeIII(μ-O)(μ-CH3CO2)2FeIII(tpb) (4(PF6))及其单电子氧化形式[4ox]2+。最后，已知的异双核物种(Me3[9]环壬三胺)CrIII(μ-O)(μ-CH3CO2)2Fe([9]环壬三胺)2 (5(PF6)2)也可以进行单电子氧化，生成含有铁(IV)离子的[5ox]3+。通过X射线晶体学确定了4(PF6)·0.5CH3CN·0.25(C2H5)2O的结构，通过Fe K边扩展X射线吸收精细结构光谱（Fe(IV)-O(氧代)：1.69(1) Å；Fe(IV)-O(羧酸根) 1.93(3) Å，Fe(IV)-N 2.00(2) Å）确定了[5ox]2+的结构，这与5的数据（Fe(III)-O(氧代) 1.80 Å；Fe(III)-O(羧酸根) 2.05 Å，Fe-N 2.20 Å）形成对比。[5ox]2+具有St = 1/2基态，而所有含有混合价态[FeIV(μ-O)(μ-CH3CO2)2FeIII]3+核心的配合物都具有St = 3/2基态。配合物氧化形式的穆斯堡尔光谱清楚地显示存在低自旋FeIV离子（在80 K时，同质异能位移约为0.02 mm s(-1)，四极分裂约为1.4 mm s(-1)），而高自旋FeIII离子表现出δ约为0.46 mm s(-1)和ΔE(Q)约为0.5 mm s(-1)。通过密度泛函理论方法在BP86和B3LYP水平上计算了穆斯堡尔、电子顺磁共振光谱和结构参数。对于具有混合价态FeIV-FeIII核心的二铁配合物（H = -2J S1·S2；S(1) = 5/2；S2 = 1）计算出的交换耦合常数J为-88 cm(-1)（分子内反铁磁耦合），对于还原的二铁形式计算出的J为-75 cm(-1)，与实验结果（J = -120 cm(-1)）合理吻合。