Kariyawasam Pathirana Kavindu Dilshan, Ghosh Pokhraj, Hsieh Chung-H, Elrod Lindy Chase, Bhuvanesh Nattamai, Darensbourg Donald J, Darensbourg Marcetta Y
Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States.
Department of Chemistry, Tamkang University, New Taipei City, Taiwan.
Inorg Chem. 2020 Mar 16;59(6):3753-3763. doi: 10.1021/acs.inorgchem.9b03409. Epub 2020 Feb 21.
The development of ligands with specific stereo- and electrochemical requirements that are necessary for catalyst design challenges synthetic chemists in academia and industry. The crucial aza-dithiolate linker in the active site of [FeFe]-Hase has inspired the development of synthetic analogues that utilize ligands which serve as conventional σ donors with pendant base features for H binding and delivery. Several MNS complexes (M = Ni, [Fe(NO)], [Co(NO)], etc.) utilize these cis-dithiolates to bind low valent metals and also demonstrate the useful property of hemilability, i.e., alternate between bi- and monodentate ligation. Herein, synthetic efforts have led to the isolation and characterization of three heterotrimetallics that employ metallodithiolato ligand binding to di-iron scaffolds in three redox levels, (μ-pdt)[Fe(CO)], (μ-pdt)[Fe(CO)][(Fe(NO))(IMe)(CO)], and (μ-pdt)(μ-H)[Fe(CO)(PMe)] to generate (μ-pdt)[(Fe(CO)][Fe(CO)·NiNS] (), (μ-pdt)[Fe(CO)][(Fe(NO))(IMe)(CO)] (), and (μ-pdt)(μ-H)[Fe(CO)(PMe)][Fe(CO)(PMe)·NiNS] () complexes (pdt = 1,3-propanedithiolate, IMe = 1,3-dimethylimidazole-2-ylidene, NiNS = [N,N'-bis(2-mercaptidoethyl)-1,4-diazacycloheptane] nickel(II)). These complexes display efficient metallodithiolato binding to the di-iron scaffold with one thiolate-S, which allows the free unbound thiolate to potentially serve as a built-in pendant base to direct proton binding, promoting a possible Fe-H···H-S coupling mechanism for the electrocatalytic hydrogen evolution reaction (HER) in the presence of acids. Ligand substitution studies on indicate an associative/dissociative type reaction mechanism for the replacement of the NiNS ligand, providing insight into the Fe-S bond strength.
设计催化剂所需的具有特定立体和电化学要求的配体的开发，对学术界和工业界的合成化学家构成了挑战。[FeFe]-氢化酶活性位点中至关重要的氮杂二硫醇盐连接基激发了合成类似物的开发，这些类似物利用配体作为传统的σ供体，具有用于氢结合和传递的侧基碱基特征。几种MNS配合物（M = Ni、[Fe(NO)]、[Co(NO)]等）利用这些顺式二硫醇盐结合低价金属，并且还表现出半不稳定的有用性质，即在双齿和单齿配位之间交替。在此，合成工作已导致分离和表征了三种异三金属化合物，它们在三个氧化还原水平上采用金属二硫醇盐配体与双铁支架结合，(μ- pdt)[Fe(CO)]、(μ- pdt)[Fe(CO)][(Fe(NO))(IMe)(CO)]和(μ- pdt)(μ- H)[Fe(CO)(PMe)]，以生成(μ- pdt)[(Fe(CO)][Fe(CO)·NiNS] ()、(μ- pdt)[Fe(CO)][(Fe(NO))(IMe)(CO)] ()和(μ- pdt)(μ- H)[Fe(CO)(PMe)][Fe(CO)(PMe)·NiNS] ()配合物（pdt = 1,3 - 丙二硫醇盐，IMe = 1,3 - 二甲基咪唑 - 2 - 亚基，NiNS = [N,N'-双(2 - 巯基乙基)-1,4 - 二氮杂环庚烷]镍(II)）。这些配合物显示出金属二硫醇盐与双铁支架通过一个硫醇盐 - S的有效结合，这使得游离的未结合硫醇盐有可能作为内置的侧基碱基来引导质子结合，在有酸存在的情况下促进电催化析氢反应（HER）中可能的Fe - H···H - S偶联机制。对 的配体取代研究表明，NiNS配体取代的反应机制为缔合/解离型，这为了解Fe - S键强度提供了线索。
