Metal-Micelle Cooperativity: Phosphine Ligand-Free Ultrasmall Palladium(II) Nanoparticles for Oxidative Mizoroki-Heck-type Couplings in Water at Room Temperature.
Metal-Micelle Cooperativity: Phosphine Ligand-Free Ultrasmall Palladium(II) Nanoparticles for Oxidative Mizoroki-Heck-type Couplings in Water at Room Temperature.
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DOI：
10.1021/jacsau.0c00087
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发表时间：
2021-03-22
期刊：
影响因子：
8
通讯作者：
Handa S
中科院分区：
文献类型：
--
作者：
Ansari TN;Jasinski JB;Leahy DK;Handa S
两亲物PS-750-M可从Pd（OAc）2生成稳定、无膦配体且具有催化活性的超小Pd（II）纳米颗粒（NPs），从而防止其沉淀、聚合和氧化态变化。PS-750-M直接与Pd（II）NP表面相互作用，通过高分辨率质谱和IR光谱证实，从而获得高稳定性。NP中的Pd阳离子最有可能通过氢氧化物和乙酸根离子保持在一起。通过高分辨透射电镜（HRTEM）、高分辨质谱（HRMS）和红外光谱（IR）对纳米粒子进行了表征，揭示了纳米粒子的形貌和粒径分布，为纳米粒子与两亲分子的相互作用提供了证据。NP催化活性的上下文中的氧化Mizoroki-Heck型偶联在水中在室温下进行了检查。热过滤、热萃取和三相测试表明，在胶束界面发生的是非均相催化，而不是在溶液中发生的均相催化。核磁共振研究表明，催化活性源于苯乙烯的金属阳离子-π相互作用，沿着芳基硼酸的金属转移作用，然后插入和β-H消除以提供偶联产物，沿着钯的再氧化。通过苯醌完成催化循环。这种方法在NP合成和随后的催化方面都是非常温和和可持续的，并且显示出广泛的底物范围，同时避免了这类重要偶联对有机溶剂的需求。
The amphiphile PS-750-M generates stable, phosphine ligand-free, and catalytically active ultrasmall Pd(II) nanoparticles (NPs) from Pd(OAc)2, preventing their precipitation, polymerization, and oxidation state changes. PS-750-M directly interacts with Pd(II) NP surfaces, as confirmed by high-resolution mass spectrometry and IR spectroscopy, resulting in their high stability. The Pd cations in NPs are most likely held together by hydroxides and acetate ions. The NPs were characterized by HRTEM, revealing their morphology and particle size distribution, and by HRMS and IR, providing evidence for NP–amphiphile interaction. The NP catalytic activity was examined in the context of oxidative Mizoroki–Heck-type couplings in water at room temperature. Hot filtration, hot extraction, and three-phase tests indicate heterogeneous catalysis occurring at the micellar interface rather than homogeneous catalysis occurring in the solution. NMR studies indicate that the catalytic activity stems from metal cation−π interactions of the styrene along with transmetalation by the arylboronic acid, followed by insertion and β-H elimination to furnish the coupled product along with the reoxidation of Pd by benzoquinone to complete the catalytic cycle. This method is very mild and sustainable, both in terms of NP synthesis and subsequent catalysis, and shows broad substrate scope while circumventing the need for organic solvents for this important class of couplings.
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