Bioinspired CNP Iron(II) Pincers Relevant to [Fe]-Hydrogenase (Hmd): Effect of Dicarbonyl versus Monocarbonyl Motifs in H 2 Activation and Transfer Hydrogenation
Bioinspired CNP Iron(II) Pincers Relevant to [Fe]-Hydrogenase (Hmd): Effect of Dicarbonyl versus Monocarbonyl Motifs in H 2 Activation and Transfer Hydrogenation
复制标题
与 [Fe]-氢化酶 (Hmd) 相关的仿生 CNP 铁 (II) 钳：二羰基与单羰基基序在 H 2 活化和转移氢化中的影响
DOI：
10.1021/acs.inorgchem.9b03476
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发表时间：
2020
影响因子：
4.6
通讯作者：
Rose, Michael J.
中科院分区：
文献类型：
--
作者：
Xie, Zhu-Lin;Chai, Wenrui;Kerns, Spencer A.;Henkelman, Graeme A.;Rose, Michael J.
报告了一组与[Fe]-氢化酶（Hmd）相关的生物启发的氨基甲酰基CNP钳形复合物。二羰基物种[（CNHNNHPR 2）Fe（CO）2 I] [R = Ph，1; R =iPr，2]经历配体去质子化，产生式[（CNHNN= PR 2）Fe（CO）2]的脱芳构化络合物（5和6）。碘键合的脱芳构化产物[Na（18-冠-6）][（CNHNN= PPh 2）Fe（CO）2 I]（7）的晶体结构和~ 1H {31 P} NMR谱表明，脱质子部分是磷胺N（H）键。分别合成了单羰基配合物[（CNHNNHPR 2）Fe（CO）（MeCN）2]（BF 4）（8和9），并以类似的方式进行了脱质子和脱芳构化。反应性研究表明，parentdicarbonylcomplex需要更有力的条件H2活化，相比themonocarbonylcomplex。在两种情况下均未发现配体骨架参与H2活化，也未观察到H2→氢化物向有机底物的转移。密度泛函理论计算表明，单羰基配合物对H2的高亲和力是其裂解H2的主要原因.这一行为归因于两个关键点有关的必需的π（Fe）→ σ*（H2）的背键相互作用在传统的M-H2 Kubas相互作用：（i）一般来说，较弱的π给体能力的二羰基化合物，和（ii）具体地说，一个强π酸性CO配体（相对于弱π酸性MeCN配体）的不利影响，反式到H2活化位点。单羰基配合物的高反应活性也被单羰基8的催化转移氢化所证明，而双羰基1是无效的。总的来说，结果表明，自然界使用[Fe]-氢化酶中的二羰基基序来减少Fe中心和二氢之间的相互作用，从而防止在底物（H4 MPT+）结合之前过早的H2活化和任何由此产生的非特异性氢化物转移反应性。
A set of bioinspired carbamoyl CNP pincer complexes are reported that are relevant to [Fe]-hydrogenase (Hmd). Thedicarbonylspecies [(CNHNNHPR2)Fe(CO)2I] [R = Ph,1; R =iPr,2] undergoes ligand deprotonation, resulting in the dearomatized complexes of formulas [(CNHNN=PR2)Fe(CO)2] (5and6). The crystal structure and1H{31P} NMR spectroscopy of the iodide-bound dearomatized species [Na(18-crown-6)][(CNHNN=PPh2)Fe(CO)2I] (7) showed that the deprotonated moiety was the phosphoramine N(H) linkage. Separately, themonocarbonylcomplexes [(CNHNNHPR2)Fe(CO)(MeCN)2](BF4) (8and9) synthesized, as well as deprotonated and dearomatized in similar fashion. Reactivity studies revealed that the parentdicarbonylcomplexes require more forceful conditions for H2activation, compared with themonocarbonylcomplexes. The ligand backbone was not found to participate in H2activation and H2→ hydride transfer to an organic substrate was not observed in either case. Density functional theory calculations revealed that the higher reactivity of themonocarbonylcomplex in H2splitting could be attributed to its higher affinity for H2. This behavior is attributed to two key points related to the requisitedπ(Fe) → σ*(H2) back-bonding interaction in a conventional M–H2Kubas interaction: (i) generally, the weaker π donor capacity of the dicarbonyls, and (ii) specifically, the detrimental effect of a strongly π acidic CO ligand (versus weakly π acidic MeCN ligand) trans to the H2activation site. The higher reactivity of themonocarbonylcomplex is also evidenced by the catalytic transfer hydrogenation bymonocarbonyl8, whereasdicarbonyl1was ineffective. Overall, the results suggest that Nature uses the dicarbonyl motif in [Fe]-hydrogenase todiminishthe interaction between the Fe center and dihydrogen, thereby preventing premature H2activation prior to substrate (H4MPT+) binding and any resulting nonspecific hydride transfer reactivity.