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首页> 外文期刊>Chemistry: A European journal >Mechanism of Redox-Active Ligand-Assisted Nitrene-Group Transfer in a Zr-IV Complex: Direct Ligand-to-Ligand Charge Transfer Preferred
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Mechanism of Redox-Active Ligand-Assisted Nitrene-Group Transfer in a Zr-IV Complex: Direct Ligand-to-Ligand Charge Transfer Preferred

机译：Zr-IV配合物中氧化还原活性配体辅助的硝基基团转移的机制：直接配体到配体电荷转移的首选

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摘要

The mechanism of the nitrene-group transfer reaction from an organic azide to isonitrile catalyzed by a Zr-IV d(0) complex carrying a redox-active ligand was studied by using quantum chemical molecular-modeling methods. The key step of the reaction involves the two-electron reduction of the azide moiety to release dinitrogen and provide the nitrene fragment, which is subsequently transferred to the isonitrile substrate. The reducing equivalents are supplied by the redox-active bis(2-iso-propylamido-4-methoxyphenyl)amide ligand. The main focus of this work is on the mechanism of this redox reaction, in particular, two plausible mechanistic scenarios are considered: 1) the metal center may actively participate in the electron-transfer process by first recruiting the electrons from the redox-active ligand and becoming formally reduced in the process, followed by a classical metal-based reduction of the azide reactant. 2) Alternatively, a non-classical, direct ligand-to-ligand chargetransfer process can be envisioned, in which no appreciable amount of electron density is accumulated at the metal center during the course of the reaction. Our calculations indicate that the non-classical ligand-to-ligand charge-transfer mechanism is much more favorable energetically. Utilizing a series of carefully constructed putative intermediates, both mechanistic scenarios were compared and contrasted to rationalize the preference for ligand-to-ligand charge-transfer mechanism.
机译：通过使用量子化学分子建模方法研究了带有氧化还原活性配体的Zr-IV d（0）配合物催化的有机叠氮化物到异腈腈基转移反应的机理。该反应的关键步骤涉及叠氮化物部分的两电子还原以释放二氮并提供腈片段，该片段随后被转移至异腈底物。还原当量由氧化还原活性双（2-异丙基酰胺基-4-甲氧基苯基）酰胺配体提供。这项工作的主要重点是氧化还原反应的机理，特别是考虑了两个可能的机理：1）金属中心可以通过首先从氧化还原活性配体中吸收电子来积极参与电子转移过程。并在此过程中被正式还原，然后是经典的基于金属的叠氮化物反应物还原。 2）可替代地，可以设想一种非经典的，直接的配体到配体的电荷转移方法，其中在反应过程中在金属中心没有可观数量的电子密度积累。我们的计算表明，非经典的配体到配体的电荷转移机理在能量上更为有利。利用一系列精心构建的推定中间体，对两种机理进行了比较和对比，以合理化对配体-配体电荷转移机制的偏好。

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