Isomerization of the hydride complexes [HFe2(SR)2(PR3)(x)(CO)(6-x)]+ (x = 2, 3, 4) relevant to the active site models for the [FeFe]-hydrogenases.
Isomerization of the hydride complexes [HFe2(SR)2(PR3)(x)(CO)(6-x)]+ (x = 2, 3, 4) relevant to the active site models for the [FeFe]-hydrogenases.
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DOI：
10.1039/b910147k
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发表时间：
2010-03-28
期刊：
影响因子：
--
通讯作者：
Wilson SR
中科院分区：
文献类型：
--
作者：
Barton BE;Zampella G;Justice AK;De Gioia L;Rauchfuss TB;Wilson SR
讨论了二硫代铁的桥联(μ-)氢化物的逐步形成，重点讨论了质子化和随后的异构化的途径。我们的证据与质子化发生在单个Fe中心，然后是一系列μ氢化物的异构化是一致的。Fe_2(Edt)(CO)_4(Dppv)(1)质子化得到一种μ氢化物，dppv横跨顶端和基端，在较高的温度下异构化，使dppv处于双碱基位置。Fe2(Pdt)(CO)4(Dppv)(2)的质子化反应遵循与[1H]+类似的异构化途径，只是在Fe(CO)3或Fe(CO)(Dppv)位质子化最初观察到一对异构化末端氢化物.三膦氢Fe2(Edt)(CO)3(PMe3)(Dppv)(3)低温质子化的第一个可观察到的产物是单一的μ氢化物，其中pme3是顶端的，dppv配体跨越顶端和基端。升温后，这一异构体完全但逐步转化为其他三种同分异构体氢化物的混合物。Fe2(Pdt)(CO)3(PMe3)(Dppv)(4)的质子化过程与EDT类似物3相似，但观察到末端氢化物，尽管只是在很低的温度(−90°C)下观察到短暂的氢化物。双络合物Fe_2(Xdt)(CO)_2(Dppv)_2低温质子化只生成末端氢化物[HFe_2(Xdt)(μ-CO)(CO)(Dppv)_2]+(xdt=edt和pdt)，然后异构化成一对μ-氢化物。在室温下，这些(Dppv)2衍生物转化为两个异构体的平衡，一个是C2对称的，另一个是Cs对称的。末端氢化物的稳定性与(C2-异构体)/(Cs-异构体)平衡比有关，它反映了二硫代硫酸盐的大小。异构化反应不受过量酸、溶剂极性和D2O存在的影响。这种异构化机理被认为是分子内的，包括HFeL3亚基120°旋转到未观察到的末端碱基氢化物作为速率决定步骤。密度泛函理论计算证实了氢化物的稳定性，这也突出了基端氢化物的不稳定性。μ-氢化物异构体在交替的FeL3上通过120°旋转发生异构化，不产生D2O可交换的中间体。
The stepwise formation of bridging (μ-) hydrides of diiron dithiolates is discussed with attention on the pathway for protonation and subsequent isomerizations. Our evidence is consistent with protonations occurring at a single Fe center, followed by isomerization to a series of μ-hydrides. Protonation of Fe2(edt)(CO)4(dppv) (1) gave a single μ-hydride with dppv spanning apical and basal sites, which isomerized at higher temperatures to place the dppv into a dibasal position. Protonation of Fe2(pdt)(CO)4(dppv) (2) followed an isomerization pathway similar to that for [1H]+, except that a pair of isomeric terminal hydrides were observed initially, resulting from protonation at the Fe(CO)3 or Fe(CO)(dppv) site. The first observable product from low temperature protonation of the tris-phosphine Fe2(edt)(CO)3(PMe3)(dppv) (3) was a single μ-hydride wherein PMe3 is apical and the dppv ligand spans apical and basal sites. Upon warming, this isomer converted fully but in a stepwise manner to a mixture of three other isomeric hydrides. Protonation of Fe2(pdt)(CO)3(PMe3)(dppv) (4) proceeded similarly to the edt analogue 3, however a terminal hydride was observed, albeit only briefly and at very low temperatures (−90 °C). Low-temperature protonation of the bis-chelates Fe2(xdt)(CO)2(dppv)2 produced exclusively the terminal hydrides [HFe2(xdt)(μ-CO)(CO)(dppv)2]+ (xdt = edt and pdt), which subsequently isomerized to a pair of μ-hydrides. At room temperature these (dppv)2 derivatives convert to an equilibrium of two isomers, one C2-symmetric and the other Cs-symmetric. The stability of the terminal hydrides correlates with the (C2-isomer)/(Cs-isomer) equilibrium ratio, which reflects the size of the dithiolate. The isomerization was found to be unaffected by the presence of excess acid, by solvent polarity, and the presence of D2O. This isomerization mechanism is proposed to be intramolecular, involving a 120° rotation of the HFeL3 subunit to an unobserved terminal basal hydride as the rate-determining step. The observed stability of the hydrides was supported by DFT calculations, which also highlight the instability of the basal terminal hydrides. Isomerization of the μ-hydride isomers occurs on alternating FeL3 via 120° rotations without generating D2O-exchangeable intermediates.
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影响因子：
2.3
作者：
Adam, Fatima I.;Hogarth, Graeme;Richards, Idris
通讯作者：
Richards, Idris
影响因子：
4.6
作者：
Bruschi, Maurizio;Greco, Claudio;De Gioia, Luca
通讯作者：
De Gioia, Luca
影响因子：
4.6
作者：
Cheah, MH;Borg, SJ;Best, SP
通讯作者：
Best, SP
[FEFE] - 氢化酶的活性位点的混合价模型的氧化还原和结构特性：进步和挑战。
影响因子：
4.6
作者：
Justice AK;De Gioia L;Nilges MJ;Rauchfuss TB;Wilson SR;Zampella G
通讯作者：
Zampella G
影响因子：
16.6
作者：
Bruschi, Maurizio;Greco, Claudio;De Gioia, Luca
通讯作者：
De Gioia, Luca