Intramolecular iron-mediated C-H bond heterolysis with an assist of pendant base in a [FeFe]-hydrogenase model.
Intramolecular iron-mediated C-H bond heterolysis with an assist of pendant base in a [FeFe]-hydrogenase model.
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DOI：
10.1021/ja5078014
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发表时间：
2014-10
影响因子：
15
通讯作者：
D. Zheng;Ning Wang;Mei Wang;Shengda Ding;Cheng-Bing Ma;M. Darensbourg;M. Hall;Licheng Sun
中科院分区：
文献类型：
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作者：
D. Zheng;Ning Wang;Mei Wang;Shengda Ding;Cheng-Bing Ma;M. Darensbourg;M. Hall;Licheng Sun
虽然许多含铁金属酶在生物C-H活化过程中起着重要作用，但迄今为止，铁介导的C（sp（3））-H异源裂解还没有报道用于Fe/S-金属酶的合成模型。相比之下，大量的先例已经确定，自然界的设计可逆氢活化的二铁氢化酶（[FeFe]-H2酶）活性位点涉及多个铁，硫桥，氧化还原开关，和一个悬垂胺碱，在一个复杂的安排，以执行H-H异裂。为了回答这种策略是否可能扩展到C-H活化，我们报告了[FeFe]-H2 ase模型，该模型通过agostic C-H相互作用证明了铁介导的分子内C-H异裂，通过附近的侧基胺去除质子，提供Fe（II）-[Fe '（II）-CH-S]三元环产物，其可以在HBF 4存在下通过Cp 2Co还原回1。作为质子穿梭的侧基的功能被证实的N-质子化的中间体和最终的去质子化的产品的晶体结构相比，类似的，但侧基-胺-免费的复杂，不显示C-H激活的证据。该过程的机理得到了DFT计算的支持。
Although many metalloenzymes containing iron play a prominent role in biological C-H activation processes, to date iron-mediated C(sp(3))-H heterolysis has not been reported for synthetic models of Fe/S-metalloenzymes. In contrast, ample precedent has established that nature's design for reversible hydrogen activation by the diiron hydrogenase ([FeFe]-H2ase) active site involves multiple irons, sulfur bridges, a redox switch, and a pendant amine base, in an intricate arrangement to perform H-H heterolytic cleavage. In response to whether this strategy might be extended to C-H activation, we report that a [FeFe]-H2ase model demonstrates iron-mediated intramolecular C-H heterolytic cleavage via an agostic C-H interaction, with proton removal by a nearby pendant amine, affording Fe(II)-[Fe'(II)-CH-S] three-membered-ring products, which can be reduced back to 1 by Cp2Co in the presence of HBF4. The function of the pendant base as a proton shuttle was confirmed by the crystal structures of the N-protonated intermediate and the final deprotonated product in comparison with that of a similar but pendant-amine-free complex that does not show evidence of C-H activation. The mechanism of the process was backed up by DFT calculations.