Reactivities of Fe(IV) complexes with oxo, hydroxo, and alkylperoxo ligands: an experimental and computational study.
Reactivities of Fe(IV) complexes with oxo, hydroxo, and alkylperoxo ligands: an experimental and computational study.
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DOI：
10.1021/ic901391y
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发表时间：
2009-12-07
影响因子：
4.6
通讯作者：
Que, Lawrence, Jr.
中科院分区：
文献类型：
--
作者：
Fiedler, Adam T.;Que, Lawrence, Jr.
在之前的一篇论文中(Jensen等人，J.Am化学。SoC。2005.127,10512)合成了绿松石色中间体[FeIV(β-BPMCN)(OOtBu)(OH)]2+(TQ；BPMCN=N，N‘-双(2-吡啶甲基)-N，N’-二甲基-反式-1，2-二氨基环己烷)。TQ的结构是史无前例的，因为它是迄今为止唯一一个同时具有烷基过氧基和氢氧化物配体的非血红素FeIV络合物的合成例子。考虑到类似的高价铁中间体在加氧酶作用机制中的重要性，我们研究了TQ在70℃下的反应活性，发现它能够激活弱X-H键(X=C，O)，键的解离能为−~80kcal/≤。执行初始H原子提取的是TQ的FeIV-OH单元，而不是烷基过氧基部分。然而，在−45°C时，TQ的衰减速度与底物的一致性和浓度无关，形成了一种能够氧化具有更强C-H键的底物的物种。相关的氧化铁(IV)配合物[FeIV(β-BPMCN)(O)(X)]2+(3-X；X=吡啶或腈)也进行了平行反应性研究，从而允许直接比较FeIV中心与氧和氢氧化物配体的反应性。我们发现，FeIV=O物种的氢原子抽提能力大大超过FeIV-OH物种，一般是FeIV-OH物种的100倍以上。用密度泛函理论(DFT)研究了TQ和3-X的电子结构，为它们不同的反应活性提供了理论基础。
In a previous paper (Jensen et al., J. Am. Chem. Soc. 2005, 127, 10512), we reported the synthesis of the turquoise-colored intermediate [FeIV(β-BPMCN)(OOtBu)(OH)]2+ (Tq; BPMCN = N,N′-bis(2-pyridylmethyl)-N,N′-dimethyl-trans-1,2-diaminocyclohexane). The structure of Tq is unprecedented, as it represents the only synthetic example to date of a non-heme FeIV complex with both alkylperoxo and hydroxide ligands. Given the significance of similar high-valent Fe intermediates in the mechanisms of oxygenase enzymes, we have explored the reactivity of Tq at −70 °C, a temperature at which it is stable, and found that it is capable of activating weak X-H bonds (X = C, O) with bond dissociation energies ≤~80 kcal/mol. The FeIV-OH unit of Tq, and not the alkylperoxo moiety, performs the initial H-atom abstraction. However at −45 °C, Tq decays at a rate that is independent of substrate identity and concentration, forming a species capable of oxidizing substrates with stronger C-H bonds. Parallel reactivity studies were also conducted with the related oxoiron(IV) complexes [FeIV(β-BPMCN)(O)(X)]2+ (3-X; X = pyridine or nitrile), thereby permitting a direct comparison of the reactivity of FeIV centers with oxo and hydroxide ligands. We found that the H-atom abstracting ability of the FeIV=O species greatly exceeds that of the FeIV-OH species, generally by greater than 100-fold. Examination of the electronic structures of Tq and 3-X with density functional theory (DFT) provides a rationale for their differing reactivities.
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影响因子：
16.6
作者：
Klinker, Eric J.;Shaik, Sason;Hirao, Hajime;Que, Lawrence, Jr.
通讯作者：
Que, Lawrence, Jr.
影响因子：
3.6
作者：
Lucarini, M;Pedrielli, P;Fattuoni, C
通讯作者：
Fattuoni, C
影响因子：
16.6
作者：
Klinker, EJ;Kaizer, J;Que, L
通讯作者：
Que, L
影响因子：
4.4
作者：
BECKE, AD
通讯作者：
BECKE, AD
影响因子：
15
作者：
Kaizer, J;Klinker, EJ;Que, L
通讯作者：
Que, L