Characterization of a tricationic trigonal bipyramidal iron(IV) cyanide complex, with a very high reduction potential, and its iron(II) and iron(III) congeners.
Characterization of a tricationic trigonal bipyramidal iron(IV) cyanide complex, with a very high reduction potential, and its iron(II) and iron(III) congeners.
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DOI：
10.1021/ic102094d
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发表时间：
2011-04-04
影响因子：
4.6
通讯作者：
Que L Jr
中科院分区：
文献类型：
--
作者：
England J;Farquhar ER;Guo Y;Cranswick MA;Ray K;Münck E;Que L Jr
目前，只有少数合成的S = 2氧代铁（IV）配合物。这些作为模型的高自旋（S = 2）oxoiron（IV）的物种已被假定，并在几种情况下，作为关键的中间体在催化循环的各种非血红素氧活化酶确认。三角双锥配合物[FeIV（O）（TMG 3 tren）]2+（1）是第一个高产率生成的S = 2氧代铁（IV）模型配合物，也是第一个进行晶体学表征的配合物。在这项研究中，我们证明了TMG 3 tren配体也能够支持三阳离子氰基铁（IV）单元[FeIV（CN）（TMG 3 tren）]3+（4）。该络合物是通过电解氧化高自旋（S = 2）铁（II）络合物[FeII（CN）（TMG 3 tren）]+（2），经由S = 5/2络合物[FeIII（CN）（TMG 3 tren）]2+（3）产生的，其过程通过使用紫外-可见光谱法方便地监测，以跟踪向红迁移的LMCT谱带的生长。XAS、穆斯堡尔谱和NMR光谱的组合被用来确定4具有S = 0铁（IV）中心。与其抗磁性铁（IV）基态一致，EXAFS分析4表明铁供体原子键长的显着收缩，相对于那些晶体学特征的配合物2和3。值得注意的是，4具有相对于Fc+/o约1.4V的FeIV/III还原电位，这是对于单铁络合物观察到的最高值。4的相对高的稳定性（在含有0.1 M KPF 6的CD 3CN溶液中，在25 °C下的t1/2 = 15 min），反映在其通过缓慢的本体电解的高产率积累和在−40 °C下对13 C NMR的顺从性，突出了TMG 3 tren配体的空间保护的高碱性全烷基胍基供体支持高度带电的高价络合物的能力。
Currently, there are only a handful of synthetic S = 2 oxoiron(IV) complexes. These serve as models for the high-spin (S = 2) oxoiron(IV) species that have been postulated, and confirmed in several cases, as key intermediates in the catalytic cycles of a variety of non-heme oxygen activating enzymes. The trigonal bipyramidal complex [FeIV(O)(TMG3tren)]2+ (1) was both the first S = 2 oxoiron(IV) model complex to be generated in high yield and the first to be crystallographically characterized. In this study, we demonstrate that the TMG3tren ligand is also capable of supporting a tricationic cyanoiron(IV) unit, [FeIV(CN)(TMG3tren)]3+ (4). This complex was generated by electrolytic oxidation of the high-spin (S = 2) iron(II) complex [FeII(CN)(TMG3tren)]+ (2), via the S = 5/2 complex [FeIII(CN)(TMG3tren)]2+ (3), the progress of which was conveniently monitored by using UV-Vis spectroscopy to follow the growth of bathochromically shifting LMCT bands. A combination of XAS, Mössbauer and NMR spectroscopies was used to establish that 4 has a S = 0 iron(IV) center. Consistent with its diamagnetic iron(IV) ground state, EXAFS analysis of 4 indicated a significant contraction of the iron-donor atom bond lengths, relative to those of the crystallographically characterized complexes 2 and 3. Notably, 4 has an FeIV/III reduction potential of ~1.4 V vs Fc+/o, the highest value yet observed for a monoiron complex. The relatively high stability of 4 (t1/2 in CD3CN solution containing 0.1 M KPF6 at 25 °C ≈ 15 min), as reflected by its high-yield accumulation via slow bulk electrolysis and amenability to 13C NMR at −40 °C, highlights the ability of the sterically protecting, highly basic peralkylguanidyl donors of the TMG3tren ligand to support highly charged high-valent complexes.
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DOI：
10.1039/dt9840001349
发表时间：
1984-01-01
期刊：
JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS
影响因子：
--
作者：
ADDISON, AW;RAO, TN;VERSCHOOR, GC
通讯作者：
VERSCHOOR, GC
影响因子：
4.6
作者：
Britovsek, GJP;England, J;White, AJP
通讯作者：
White, AJP
影响因子：
15
作者：
Dey, Abhishek;Hocking, Rosalie K.;Solomon, Edward I.
通讯作者：
Solomon, Edward I.
影响因子：
2.9
作者：
HAN, SW;MADDEN, JF;SPIRO, TG
通讯作者：
SPIRO, TG
影响因子：
15
作者：
Eser, Bekir E.;Barr, Eric W.;Fitzpatrick, Paul F.
通讯作者：
Fitzpatrick, Paul F.