Synthesis, crystal structure, and catalytic activity of bridged-bis(N-heterocyclic carbene) palladium(II) complexes in selective Mizoroki-Heck cross-coupling reactions
作者:Waseem Mansour、Rami Suleiman、Wissam Iali、Mohammed Fettouhi、Bassam El Ali
DOI:10.1016/j.poly.2021.115371
日期:2021.10
temperature range 25–120 °C. The catalytic activities of three Pd-bridged bis(NHC) complexes in the Mizoroki-Heck cross-coupling reactions were not found to have a direct correlation with +I effect order of the N-substituents of the ligand. However, a direct correlation was found between the DFT calculated absolute softness of the three complexes with their respective catalytic activity. The highest calculated
一系列三个 1,3-丙二基桥连双(N-杂环卡宾)钯(II)配合物(Pd-BNH1、Pd-BNH2和Pd-BNH3),配体的N-取代基具有 + I 效应顺序(异丙基 > 苄基 > 甲氧基苯基),是光谱、结构、计算和催化研究的主题。在芳基溴化物与苯乙烯或丙烯酸酯衍生物的 Mizoroki-Heck 偶联反应中评估了双 (NHC)PdBr 2配合物,并显示出生产二芳基乙烯和肉桂酸衍生物的高催化效率。最活跃的钯配合物Pd-BNH3的 X 射线结构表明 Pd(II) 中心与双 (N-杂环卡宾)和顺式位置的两个溴化物配体,导致扭曲的方形平面几何形状。Pd-BNH3的 NMR 数据与溶液中的单椅船刚性构象一致,在 25-120 °C 的温度范围内没有 8 元环钯环的动态行为。未发现在 Mizoroki-Heck 交叉偶联反应中三种 Pd 桥连双 (NHC) 配合物的催化活性与配体N取代基的+I 效应顺序直接相关。然而,发现三种复合物的