Laboratoire de Chimie, Electrochimie Moléculaire et Chimie Analytique, UMR 6521 CNRS-Université de Bretagne Occidentale, CS 93837-6 Avenue Le Gorgeu, CEDEX 3, 29238 Brest, France.
Department of Biotechnology and Bioscience, University of Milano-Bicocca Piazza della Scienza 2, 20126 Milan, Italy.
Molecules. 2022 Jul 22;27(15):4700. doi: 10.3390/molecules27154700.
The behaviour of triazolylidene ligands coordinated at a {Fe(CO)(µ-dithiolate)} core related to the active site of [FeFe]-hydrogenases have been considered to determine whether such carbenes may act as redox electron-reservoirs, with innocent or non-innocent properties. A novel complex featuring a mesoionic carbene (MIC) [Fe(CO)(Pmpt)(µ-pdt)] (; Pmpt = 1-phenyl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene; pdt = propanedithiolate) was synthesized and characterized by IR, H, C{H} NMR spectroscopies, elemental analyses, X-ray diffraction ,and cyclic voltammetry. Comparison with the spectroscopic characteristics of its analogue [Fe(CO)(Pmbt)(µ-pdt)] (; Pmbt = 1-phenyl-3-methyl-4-butyl-1,2,3-triazol-5-ylidene) showed the effect of the replacement of a n-butyl by a phenyl group in the 1,2,3-triazole heterocycle. A DFT study was performed to rationalize the electronic behaviour of , upon the transfer of two electrons and showed that such carbenes do not behave as redox ligands. With highly perfluorinated carbenes, electronic communication between the di-iron site and the triazole cycle is still limited, suggesting low redox properties of MIC ligands used in this study. Finally, although the catalytic performances of towards proton reduction are weak, the protonation process after a two-electron reduction of was examined by DFT and revealed that the protonation process is favoured by S-protonation but the stabilized diprotonated intermediate featuring a {Fe-H⋯H-S} interaction does not facilitate the release of H and may explain low efficiency towards HER (Hydrogen Evolution Reaction).
与 [FeFe]-氢化酶的活性位点相关的 {Fe(CO)(µ-二硫代物)} 核配位的三唑亚基配体的行为已被认为可以确定这些卡宾是否可以作为氧化还原电子储库，具有无辜或非无辜的性质。一种新型配合物具有介离子卡宾 (MIC) [Fe(CO)(Pmpt)(µ-pdt)] (; Pmpt = 1-苯基-3-甲基-4-苯基-1,2,3-三唑-5-亚基; pdt = 丙二硫醇) 已通过红外、H、C{H}NMR 光谱、元素分析、X 射线衍射和循环伏安法合成和表征。与类似物 [Fe(CO)(Pmbt)(µ-pdt)] 的光谱特征进行比较 (; Pmbt = 1-苯基-3-甲基-4-丁基-1,2,3-三唑-5-亚基) 表明 1,2,3-三唑杂环中 n-丁基被苯基取代的影响。进行了 DFT 研究以合理化 在转移两个电子后的电子行为，并表明这些卡宾不作为氧化还原配体。对于高度全氟化卡宾，二铁位点和三唑环之间的电子通信仍然受到限制，这表明在这项研究中使用的 MIC 配体的氧化还原性质较低。最后，尽管 对质子还原的催化性能较弱，但通过 DFT 检查了 在经历两个电子还原后的质子化过程，结果表明质子化过程有利于 S-质子化，但稳定的双质子化中间体具有 {Fe-H⋯H-S} 相互作用不利于 H 的释放，这可能解释了其对 HER（氢进化反应）的低效率。
