The Effect of Added Ligands on the Reactions of [Ni(COD)(dppf)] with Alkyl Halides: Halide Abstraction May Be Reversible.
The Effect of Added Ligands on the Reactions of [Ni(COD)(dppf)] with Alkyl Halides: Halide Abstraction May Be Reversible.
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DOI：
10.1021/acs.organomet.1c00280
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发表时间：
2021-06-28
期刊：
影响因子：
2.8
通讯作者：
Nelson DJ
中科院分区：
文献类型：
--
作者：
Greaves ME;Ronson TO;Maseras F;Nelson DJ
dppf-镍（0）与烷基卤化物的反应通过[Ni（dppf）（L）]形式的三配位镍（0）中间体进行。采用动力学实验和密度泛函理论计算研究了配体（L）的性质对催化剂形态和[Ni（COD）（dppf）]与卤代烷反应速率的影响.已经研究了一系列单齿配体，试图确定反应性的趋势。发现空间体积大的和供电子的配体降低反应速率。发现（i）卤化物提取步骤并不总是不可逆的，并且镍（I）络合物与烷基卤化物的后续重组可以对反应的总速率具有显著影响，以及（ii）一些配体导致非常稳定的[Ni（dppf）（L）2]物质。通过添加游离配体，显着提高了原型（dppf）镍催化Kumada交叉偶联反应的卤代烷的产率，这提供了另一个重要的变量，以考虑优化镍催化的卤代烷反应时。
The reactions of dppf-nickel(0) with alkyl halides proceed via three-coordinate nickel(0) intermediates of the form [Ni(dppf)(L)]. The effects of the identity of the added ligand (L) on catalyst speciation and the rates of reactions of [Ni(COD)(dppf)] with alkyl halides have been investigated using kinetic experiments and density functional theory calculations. A series of monodentate ligands have been investigated in attempts to identify trends in reactivity. Sterically bulky and electron-donating ligands are found to decrease the reaction rate. It was found that (i) the halide abstraction step is not always irreversible and the subsequent recombination of a nickel(I) complex with an alkyl halide can have a significant effect on the overall rate of the reaction and (ii) some ligands lead to very stable [Ni(dppf)(L)2] species. The yields of prototypical (dppf)nickel-catalyzed Kumada cross-coupling reactions of alkyl halides are significantly improved by the addition of free ligands, which provides another important variable to consider when optimizing nickel-catalyzed reactions of alkyl halides.
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影响因子：
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作者：
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