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首页> 外文期刊>Chemistry: A European journal >Aromatic Hydroxylation in a Copper Bis(imine) Complex Mediated by a mu-eta(2):eta(2) Peroxo Dicopper Core: A Mechanistic Scenario
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Aromatic Hydroxylation in a Copper Bis(imine) Complex Mediated by a mu-eta(2):eta(2) Peroxo Dicopper Core: A Mechanistic Scenario

机译：mu-eta（2）：eta（2）Peroxo Dicopper核介导的铜双（亚胺）络合物中的芳香羟基化：机械方案。

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摘要

Detailed mechanistic studies on the ligand hydroxylation reaction mediated by a copper bis(imine) complex are presented. Starting from a structural analysis of the Cut complex and the Cu-II product with a hydroxylated ligand, the optical absorption and vibrational spectra of starting material and product are analyzed. Kinetic analysis of the ligand hydroxylation reaction shows that O-2 binding is the rate-limiting step. The reaction proceeds much faster in methanol than in acetonitrile. Moreover, an inverse kinetic isotope effect (KIE) is evidenced for the reaction in acetonitrile, which is attributed to a sterically congested transition state leading to the peroxo adduct. In methanol, however, no KIE is observed. A DFT analysis of the oxygenation reaction mediated by the mu-eta(2):eta(2) peroxo core demonstrates that the major barrier after O-2 binding corresponds to electrophilic attack on the arene ring. The relevant orbital interaction occurs between the sigma* orbital of the Cu2O2 unit and the HOMO of the ligand. On the basis of the activation energy for the rate-limiting step (18.3 kcalmol(-1)) this reaction is thermally allowed, in agreement with the experimental observation. The calculations also predict the presence of a stable dienone intermediate which, however, escaped experimental detection so far. Reasons for these findings are considered. The implications of the results for the mechanism of tyrosinase are discussed.
机译：提出了由铜双（亚胺）配合物介导的配体羟基化反应的详细机理研究。从对Cut配合物和带有羟基化配体的Cu-II产物的结构分析开始，分析了原料和产物的光吸收和振动光谱。配体羟基化反应的动力学分析表明，O-2结合是限速步骤。在甲醇中，反应的进行比在乙腈中的进行快得多。此外，乙腈中的反应被证明具有逆动力学同位素效应（KIE），这归因于空间拥挤的过渡态，导致过氧加合物。但是，在甲醇中，未观察到KIE。对由mu-eta（2）：eta（2）过氧核心进行介导的氧化反应的DFT分析表明，O-2结合后的主要壁垒对应于对芳烃环的亲电攻击。相关的轨道相互作用发生在Cu2O2单元的sigma *轨道和配体的HOMO之间。根据限速步骤的活化能（18.3 kcalmol（-1）），与实验观察一致，该反应可以热进行。该计算还预测了稳定的二烯酮中间体的存在，但是到目前为止，它还没有通过实验检测。考虑这些发现的原因。讨论了结果对酪氨酸酶机制的影响。

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