Synthesis and Structure of Dinuclear Silver(I) and Palladium(II) Complexes of 2,7-Bis(methylene)naphthalene-Bridged Bis-N-Heterocyclic Carbene Ligands

We synthesized a series of new Ag2(bis-NHC)2 complexes from the corresponding bisimidazolium salts tethered with 2,7-dimethylnaphthalene-bridged bis-NHC ligands. The reaction proceeded in a selective manner, and the Ag2(bis-NHC)2 complexes were isolated in good to high yields. The Ag complexes were converted to the Pd2(bis-NHC)2 complexes efficiently. It is important to choose proper conditions for the conversion of the silver complexes to the palladium complexes, depending on the structure of the ligand: the effect of the counteranion was significant. The structures of the complexes were studied by X-ray crystallographic analyses and compared with the corresponding monodentate NHC complexes. The catalytic activity of the Pd complexes for the Mizoroki−Heck reaction was examined.

本研究以带有2,7-二甲基萘桥联双氮杂环卡宾（bis-NHC）配体的双咪唑鎓盐为起始原料，合成了一系列新型Ag₂(bis-NHC)₂配合物。该反应具有良好的选择性，目标Ag₂(bis-NHC)₂配合物以中等至优异的分离收率获得。上述银基配合物可高效转化为Pd₂(bis-NHC)₂配合物。需根据配体结构选择适配的转化条件，其中抗衡阴离子的影响较为显著。通过X射线晶体衍射分析表征了所得配合物的结构，并将其与相应的单齿氮杂环卡宾（monodentate NHC）配合物进行了对比。考察了该钯基配合物在Mizoroki−Heck反应中的催化活性。