Ye Jiansheng, Chen Wanzhi, Wang Daqi
Department of Chemistry, Zhejiang University, Xixi Campus, Hangzhou 310028, P. R. China.
Dalton Trans. 2008 Aug 14(30):4015-22. doi: 10.1039/b801264d. Epub 2008 Jun 19.
Pd(L1)2(CH3CN)2 (L1 = 1-n-butyl-3-(2-pyrimidyl)imidazolylidene, 3) and Pd(L2)22 (L2 = 1-(2-picolyl)-3-(2-pyrimidyl)imidazolylidene 4), prepared via carbene transfer reactions of [Ag(L1)2]PF6 (1) and Ag2(L2)22 (2) with palladium salts, respectively, have been fully characterized by 1H and 13C NMR spectroscopy and elemental analysis. The X-ray crystal structures of complexes 1-4 are reported. Complex 3 is an unusual pentacoordinated palladium complex, in which the palladium is coordinated by two imidazolylidene, two pyridine, and one acetonitrile molecule in a square-pyramidal geometry. The apical position is occupied by a pyrimidine nitrogen atom with a relatively long Pd-N distance (2.762(6) angstroms). Complex is a typical square-planar palladium complex with palladium surrounded by two pairs of cis-arranged pyridine and imidazolylidene ligands. The complexes exhibit good catalytic activities in the Heck coupling reaction of aryl bromides and activated aryl chlorides under mild conditions.
Pd(L1)2(CH3CN)2（L1 = 1 - 正丁基 - 3 - (2 - 嘧啶基)咪唑亚基，3）和Pd(L2)22（L2 = 1 - (2 - 吡啶甲基)-3 - (2 - 嘧啶基)咪唑亚基，4）分别通过[Ag(L1)2]PF6（1）和Ag2(L2)22（2）与钯盐的卡宾转移反应制备而成，已通过1H和13C NMR光谱以及元素分析进行了全面表征。报道了配合物1 - 4的X射线晶体结构。配合物3是一种不寻常的五配位钯配合物，其中钯由两个咪唑亚基、两个吡啶和一个乙腈分子以四方锥几何构型配位。顶端位置由一个嘧啶氮原子占据，Pd - N距离相对较长（2.762(6)埃）。配合物4是一种典型的平面正方形钯配合物，钯被两对顺式排列的吡啶和咪唑亚基配体包围。这些配合物在温和条件下对芳基溴化物和活性芳基氯化物的Heck偶联反应表现出良好的催化活性。
