DFT Study on Fe(IV)-Peroxo Formation and H Atom Transfer Triggered O2 Activation by NiFe Complex
DFT Study on Fe(IV)-Peroxo Formation and H Atom Transfer Triggered O2 Activation by NiFe Complex
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DOI：
10.1021/acs.organomet.8b00098
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发表时间：
2018-05-28
期刊：
影响因子：
2.8
通讯作者：
Morokuma, Keiji
中科院分区：
文献类型：
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作者：
Isegawa, Miho;Sharma, Akhilesh K.;Morokuma, Keiji
用密度泛函理论（DFT）和人工力诱导反应（AFIR）方法研究了[NiFe]-氢化酶的仿生模型配合物[NiLFe（eta（5）-C5 Me 5）]（+）[L = N，N '-二乙基-3，7-二氮杂壬烷-1，9-二硫杂环戊烯]对分子氧的活化机理.我们的计算结果表明，O-2以端对方式结合到Fe-II中心，并形成高价铁络合物（（NiFeIV）-Fe-II（eta（2）-O-2）NiFe-peroxo O-2）），这已被实验观察到。在硼氢化物（BH 4-）存在下，通过氢原子转移（HAT）发生O-O键断裂。一旦发生HAT，生成的BH 3自由基阴离子（BH 3中心点-）与NiFe-OOH的末端氧结合，产生BH 3 OH-和（NiFe IV）-Fe-II =O。BH_4 ~-与（NiFe_IV）-Fe-II=O中的氧发生第二次HAT，生成BH_3OH ~-和Fe ~-还原的络合物。重要的是，分子氧活化是由HAT触发的，而不是由质子转移或氢化物转移。O-2被Fe中心激活，并且在该过程中Fe的氧化态发生变化，而Ni的氧化态保持不变。这些对O-2激活的机理的理解对于理解氢化酶中失活状态的形成和再激活过程是必不可少的。
The mechanism for dioxygen activation using the biomimetic model complex of [NiFe]-hydrogenase, [NiLFe(eta(5)-C5Me5 )](+) [L = N,N'-diethyl-3,7-diazanonane-1,9-dithiolato] was established using density functional theory (DFT) and artificial force-induced reaction (AFIR) methods. Our computational results suggest that O-2 binds to the Fe-II center in an end-on fashion and forms a high-valent iron complex, ((NiFeIV)-Fe-II(eta(2)-O-2) NiFe-peroxo O-2)), which has been experimentally observed. The O-O bond cleavage occurs in the presence of borohydride (BH4-) through hydrogen atom transfer (HAT). Once the HAT occurs, the generated BH 3 radical anion (BH3 center dot-) binds to the terminal oxygen of NiFe-OOH, giving rise to BH3OH- and (NiFeIV)-Fe-II=O. The second HAT from BH4- to the oxygen of (NiFeIV)-Fe-II=O leads to BH3OH- and Fe-reduced complex. Importantly, the dioxygen activation is triggered by HAT, not by proton transfer or hydride transfer. The O-2 is activated by the Fe center, and the oxidation state of Fe varies during the process, while the oxidation state of Ni is conserved. These mechanistic insights into O-2 activation are essential in understanding the formation of the inactive state and reactivation process in hydrogenase.