Ranking Ligands by Their Ability to Ease (C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>Ni<sup>II</sup>L → Ni<sup>0</sup>L + (C<sub>6</sub>F<sub>5</sub>)<sub>2</sub> Coupling versus Hydrolysis: Outstanding Activity of PEWO Ligands
作者:Jaime Ponce-de-León、Estefania Gioria、Jesús M. Martínez-Ilarduya、Pablo Espinet
DOI:10.1021/acs.inorgchem.0c02831
日期:2020.12.21
PR2(biaryl) phosphines, and PEWO ligands (phosphines with one potentially chelate electron-withdrawing olefin). Extremely different C6F5–C6F5 coupling rates, ranging from totally inactive (producing stable complexes at room temperature) to those inducing almost instantaneous coupling at 25 °C, were found for the different ligands tested. The PR2(biaryl) ligands, very efficient for coupling in Pd, are slow
Ni II复合物顺式[[Ni(C 6 F 5)2(THF)2 ]是顺式-Ni(C 6 F 5)2的合成子,它使我们能够建立一个方案来测量和比较配体对Ni II →Ni 0还原消除步骤(耦合),在催化过程中通常很关键。几种不同类型的配体已提交此Ni-meter比较:联吡啶,螯合二膦,单齿膦,PR 2(联芳基)膦和PEWO配体(具有一种潜在的螯合吸电子烯烃的膦)。对于测试的不同配体,发现了完全不同的C 6 F 5 –C 6 F 5偶联速率,从完全无活性(在室温下生成稳定的复合物)到在25°C诱导几乎瞬时偶联的速率。PR 2(联芳基)配体对Pd的偶联非常有效,而在Ni中的反应缓慢且效率低下,并研究了造成这种差异的原因。相比之下,PEWO型配体效率极高,并且提供了对Ni II配合物观察到的最低偶联势垒。它们的产率高达96%C 6 F 5 –C在25°C下5分钟内完成6 F 5偶联(其余为C 6 F