美国纽约大学Tianning Diao研究组在金属有机化学研究中取得进展。他们提出了吡啶-噁唑啉配体的氧化还原活性可稳定低价有机镍自由基配合物。该项研究成果发表在2021年4月1日出版的《美国化学会杂志》上。

低价有机镍自由基络合物是交叉偶联反应和金属酶介导过程中的常见中间体。N-配体负载的镍配合物的电子结构似乎根据参与的配体和配位数的不同而变化。通过采取一种配体中心的自由基构象，一系列二价(pyrox)Ni配合物的还原产物确立了在稳定富电子的Ni(II)-烷基和芳基配合物时pyrox的氧化还原活性。还原后的pyrox又施加了更多反式构象影响。相反，这种氧化还原活性在(pyrox)Ni(I)-bromide物种中没有被观察到。

以上结果表明，pyrox在稳定富电子Ni物种方面的优异能力与其在交叉偶联反应中促进C(sp³)亲电试剂还原活化的倾向是一致的。

附：英文原文

Title: Redox Activity of Pyridine-Oxazoline Ligands in the Stabilization of Low-Valent Organonickel Radical Complexes

Author: Clifton L. Wagner, Gabriel Herrera, Qiao Lin, Chunhua T. Hu, Tianning Diao

Issue&Volume: April 1, 2021

Abstract: Low-valent organonickel radical complexes are common intermediates in cross-coupling reactions and metalloenzyme-mediated processes. The electronic structures of N-ligand supported nickel complexes appear to vary depending on the actor ligands and the coordination number. The reduction products of a series of divalent (pyrox)Ni complexes establish the redox activity of pyrox in stabilizing electron-rich Ni(II)–alkyl and aryl complexes by adopting a ligand-centered radical configuration. The reduced pyrox imparts an enhanced trans-influence. In contrast, such redox activity was not observed in a (pyrox)Ni(I)–bromide species. The excellent capability of pyrox in stabilizing electron-rich Ni species resonates with its proclivity in promoting the reductive activation of C(sp3) electrophiles in cross-coupling reactions.

DOI: 10.1021/jacs.1c00440

Source: https://pubs.acs.org/doi/10.1021/jacs.1c00440