Department of Chemistry, Zhejiang University, Xixi Campus, Hangzhou 310028, China.
Dalton Trans. 2009 Sep 21(35):7045-54. doi: 10.1039/b903285a. Epub 2009 Jun 29.
Palladium complexes, Pd(1-butyl-3-((7-methyl-1,8-naphthyridin-2-yl)methyl)imidazolylidene)22 (1), Pd(3-methyl-1-(pyrimidin-2-yl)imidazolylidene)2(CH3CN)2 (4), Pd(3-benzyl-1-(pyrimidin-2-yl)imidazolylidene)2(CH3CN)2 (5), Pd(3-ethyl-1-(pyrimidin-2-yl)imidazolylidene)2Cl (6), and [Pd(3-benzyl-1-(pyrimidin-2-yl)imidazolylidene)Cl2] (7), have been prepared via transmetallation of corresponding in situ generated silver-carbene complexes. These palladium complexes have been characterized by NMR spectroscopy and elemental analyses, and their structures were determined by X-ray single-crystal diffraction. Complexes 1 and 7 are tetracoordinate displaying square-planar geometry. Complexes 4-6 are pentacoordinate showing uncommon square-pyramidal geometry with acetonitrile or chloride at the equatorial position. The Suzuki and Hiyama coupling reactions of a wide range of aryl bromides and chlorides have been comparatively investigated by using tetracoordinate moncarbene, tetracoordinate dicarbene, and pentacoordinate dicarbene palladium complexes as catalysts. The tetracoordinate moncarbene palladium complex showed the highest catalytic activity for both coupling reactions.
钯配合物，[Pd(1-丁基-3-((7-甲基-1,8-萘啶-2-基)甲基)咪唑啉基)]2(PF6)2(1)，[Pd(3-甲基-1-(嘧啶-2-基)咪唑啉基)]2(CH3CN)](PF6)2(4)，[Pd(3-苄基-1-(嘧啶-2-基)咪唑啉基)]2(CH3CN)](PF6)2(5)，[Pd(3-乙基-1-(嘧啶-2-基)咪唑啉基)]2Cl](PF6)(6)，和[Pd(3-苄基-1-(嘧啶-2-基)咪唑啉基)]Cl2(7)，通过相应的原位生成的银卡宾配合物的转移金属化制备得到。这些钯配合物通过 NMR 光谱和元素分析进行了表征，并通过 X 射线单晶衍射确定了它们的结构。配合物 1 和 7 是四配位的，呈现出平面正方形几何形状。配合物 4-6 是五配位的，呈现出不常见的正方形金字塔几何形状，其中乙腈或氯原子位于赤道位置。通过使用四配位单卡宾、四配位双卡宾和五配位双卡宾钯配合物作为催化剂，比较研究了一系列芳基溴化物和氯化物的 Suzuki 和 Hiyama 偶联反应。四配位单卡宾钯配合物对两种偶联反应表现出最高的催化活性。
