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首页> 外文期刊>Chemistry: A European journal >Protic N-Heterocyclic Carbene Versus Pyrazole: Rigorous Comparison of Proton- and Electron-Donating Abilities in a Pincer-Type Framework
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Protic N-Heterocyclic Carbene Versus Pyrazole: Rigorous Comparison of Proton- and Electron-Donating Abilities in a Pincer-Type Framework

机译：质子的N-杂环卡宾与吡唑：钳型框架中质子和电子给定能力的严格比较

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摘要

Evaluation of the acidity of proton-responsive ligands such as protic N-heterocyclic carbenes (NHCs) bearing an NH-wingtip provides a key to understanding the metal-ligand cooperation in enzymatic and artificial catalysis. Here, we design a CNN pincer-type ruthenium complex 2 bearing protic NHC and isoelectronic pyrazole units in a symmetrical skeleton, to compare their acidities and electron-donating abilities. The synthesis is achieved by direct C-H metalation of 2-(imidazol-1-yl)-6-(pyrazol-3-yl)pyridine with [RuCl2(PPh3)(3)]. N-15-Labeling experiments confirm that deprotonation of 2 occurs first at the pyrazole side, indicating clearly that the protic pyrazole is more acidic than the NHC group. The electrochemical measurements as well as derivatization to carbonyl complexes demonstrate that the protic NHC is more electron-donating than pyrazole in both protonated and deprotonated forms.
机译：质子响应性配体（例如带有NH-翼尖的质子N-杂环卡宾（NHC））的酸度评估为理解金属和配体在酶催化和人工催化中的配合提供了关键。在这里，我们设计了一个CNN钳型钌络合物2，在对称骨架中带有质子NHC和等电子吡唑单元，以比较它们的酸度和供电子能力。合成是通过[RuCl2（PPh3）（3）]对2-（咪唑-1-基）-6-（吡唑-3-基）吡啶进行直接C-H金属化而实现的。 N-15标签实验证实2的去质子化首先发生在吡唑侧，这清楚地表明质子吡唑比NHC基团酸性更高。电化学测量以及衍生化为羰基配合物均表明质子NHC质子化和去质子化形式比吡唑具有更多的供电子性。

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