Essential Roles of Cp Ring Activation and Coordinated Solvent During Electrocatalytic H 2 Production with Fe(CpN3) Complexes
Essential Roles of Cp Ring Activation and Coordinated Solvent During Electrocatalytic H 2 Production with Fe(CpN3) Complexes
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Fe(CpN3)配合物电催化制H 2 过程中Cp环活化和配位溶剂的重要作用
DOI：
10.1021/acscatal.3c02911
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发表时间：
2023
期刊：
影响因子：
12.9
通讯作者：
Prokopchuk, Demyan E.
中科院分区：
文献类型：
--
作者：
Goel, Bhumika;Neugebauer, Hagen;VanderWeide, Andrew I.;Sánchez, Práxedes;Lalancette, Roger A.;Grimme, Stefan;Hansen, Andreas;Prokopchuk, Demyan E.
环戊二烯基（Cp）是一种典型的辅助配体平台，在电催化H-H键形成反应中可以通过配位的η5-Cp配体质子化形成η4-CpH部分而非化学无害。然而，η5-Cp环质子化的动力学，配体-金属（或金属-配体）质子转移，以及溶剂在H2生产电催化过程中的影响仍然知之甚少。我们报道了含胺功能化CpN 3配体的铁配合物电催化产氢的动力学细节，这些配体通过外源酸质子化生成η4-CpN 3 H中间体（CpN 3 = 6-氨基-1，4-二甲基-5，7-二苯基-2，3，4，6-四氢环戊二烯并[B]吡嗪-6-基）。在还原条件下，国家的最先进的DFT计算表明，协调溶剂在介导立体和区域选择性质子转移生成（内-CpN 3 H）Fe（CO）2（NCMe），与其他质子化途径是动力学上不可逾越的起着至关重要的作用。为了证明区域选择性的endo-CpN 3 H形成，等电子模型配合物（endo-CpN 3 H）Fe（CO）3被独立地制备，并且在CO下与循环氢化物中间体CpN 3FeH（CO）2的动力学研究干净地通过金属到配体的质子迁移提供了环活化的配合物（endo-CpN 3 H）Fe（CO）3。在循环过程中，络合物CpN 3FeH（CO）2与酸反应释放出H2，并再生出[CpN 3Fe（CO）2（NCMe）]+，通过密度泛函理论（DFT）发现这是TOF的决定步骤.总的来说，这些实验和计算结果强调了Cp环活化、内球溶剂化和金属-配体协同性在化学燃料合成中进行质子耦合电子转移催化的重要性。
Cyclopentadienyl (Cp), a classic ancillary ligand platform, can be chemically noninnocent in electrocatalytic H–H bond formation reactions via protonation of coordinated η5-Cp ligands to form η4-CpH moieties. However, the kinetics of η5-Cp ring protonation, ligand-to-metal (or metal-to-ligand) proton transfer, and the influence of solvent during H2production electrocatalysis remain poorly understood. We report in-depth kinetic details for electrocatalytic H2production with Fe complexes containing amine-functionalizedCpN3ligands that are protonated via exogenous acid to generate via η4-CpN3H intermediates (CpN3= 6-amino-1,4-dimethyl-5,7-diphenyl-2,3,4,6-tetrahydrocyclopenta[b]pyrazin-6-yl). Under reducing conditions, state-of-the-art DFT calculations reveal that a coordinated solvent plays a crucial role in mediating stereo- and regioselective proton transfer to generate(endo-CpN3H)Fe(CO)2(NCMe), with other protonation pathways being kinetically insurmountable. To demonstrate regioselectiveendo-CpN3H formation, the isoelectronic model complex(endo-CpN3H)Fe(CO)3is independently prepared, and kinetic studies with the on-cycle hydride intermediateCpN3FeH(CO)2under CO cleanly furnish the ring-activated complex(endo-CpN3H)Fe(CO)3via metal-to-ligand proton migration. The on-cycle complexCpN3FeH(CO)2reacts with acid to release H2and regenerate[CpN3Fe(CO)2(NCMe)]+, which was found to be the TOF-determining step via DFT. Collectively, these experimental and computational results underscore the emerging importance of Cp ring activation, inner-sphere solvation, and metal–ligand cooperativity to perform proton-coupled electron transfer catalysis for chemical fuel synthesis.