铃木反应的鲁棒高效Pd <sub>3</sub>簇催化剂及其奇机理,ACS Catalysis

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铃木反应的鲁棒高效Pd ₃簇催化剂及其奇机理
ACS Catalysis ( IF 11.3 ) Pub Date : 2017-02-08 00:00:00 , DOI: 10.1021/acscatal.6b02527
Fangyu Fu ₁ , Ji Xiang ₁ , Hao Cheng ₂ , Longjiu Cheng ₁ , Hanbao Chong ₁ , Shuxin Wang ₁ , Peng Li ₁ , Shiqiang Wei ₂ , Manzhou Zhu ₁ , Yadong Li ₃

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钯催化的Suzuki-Miyaura偶联反应是构建合成上有用的不对称芳基-芳基键的最通用和最强大的工具之一。在设计Pd团簇作为有效催化和机理研究的候选者时，可以设想研究一种介于“经典” Pd（0）L _n和Pd纳米颗粒家族之间的中间案例，尽管这种情况非常不同。在这项工作中，群集[Pd ₃ Cl（PPh ₂）₂（PPh ₃）₃ ] ⁺ [SbF ₆ ] ^-（缩写为Pd ₃ Cl）合成，并完全表征为非常坚固的框架，可在170°C的温度下稳定且完全空气稳定。发现Pd ₃ Cl在环境好氧条件下催化多种芳基溴化物和芳基硼酸的Suzuki–Miyaura C–C交叉偶联。反应在进行过程中同时通过中间Pd ₃ Ar保持了整个催化循环中簇构架的完整性，这已通过质谱分析和快速的X射线吸收精细结构得到了证明。在反应条件下不存在底物的情况下，Pd ₃ OH通过质谱法检测到这些物种，这强烈支持“金属-Pd”途径用于金属转移步骤，该步骤包括用OH取代Cl配体，然后将OH配体与芳基硼酸结合。Suzuki-Miyaura反应的动力学表明缺少诱导期，这与团簇解离的缺乏是一致的。这项研究可能为金属簇催化的CC交叉偶联反应的催化机理提供新的观点。

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A Robust and Efficient Pd3 Cluster Catalyst for the Suzuki Reaction and Its Odd Mechanism

The palladium-catalyzed Suzuki–Miyaura coupling reaction is one of the most versatile and powerful tools for constructing synthetically useful unsymmetrical aryl–aryl bonds. In designing a Pd cluster as a candidate for efficient catalysis and mechanistic investigations, it was envisaged to study a case intermediate between, although very different from, the “classic” Pd(0)L_n and Pd nanoparticle families of catalysts. In this work, the cluster [Pd₃Cl(PPh₂)₂(PPh₃)₃]⁺[SbF₆]⁻ (abbreviated Pd₃Cl) was synthesized and fully characterized as a remarkably robust framework that is stable up to 170 °C and fully air-stable. Pd₃Cl was found to catalyze the Suzuki–Miyaura C–C cross-coupling of a variety of aryl bromides and arylboronic acids under ambient aerobic conditions. The reaction proceeds while keeping the integrity of the cluster framework all along the catalytic cycle via the intermediate Pd₃Ar, as evidenced by mass spectrometry and quick X-ray absorption fine structure. In the absence of the substrate under the reaction conditions, the Pd₃OH species was detected by mass spectrometry, which strongly favors the “oxo-Pd” pathway for the transmetalation step involving substitution of the Cl ligand by OH followed by binding of the OH ligand with the arylboronic acid. The kinetics of the Suzuki–Miyaura reaction shows a lack of an induction period, consistent with the lack of cluster dissociation. This study may provide new perspectives for the catalytic mechanisms of C–C cross-coupling reactions catalyzed by metal clusters.

更新日期：2017-02-08

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