Synthesis of benzoxazolylpyridine nickel complexes and their efficient dimerization of ethylene to α-butene
作者:Rong Gao、Liwei Xiao、Xiang Hao、Wen-Hua Sun、Fosong Wang
DOI:10.1039/b807604a
日期:——
A series of new nickel complexes bearing benzoxazolylpyridines was synthesized and characterized by FT-IR spectroscopic and elemental analysis. The molecular structures of two representative complexes were determined by single-crystal X-ray diffraction. The complex [NiCl22-(2-benzoxazolyl)-6-methylpyridine}] (5) is a centrosymmetric dinuclear compound with two penta-coordinated Ni(II) centers, whereas the complex [NiCl22-(5-methyl-2-benzoxazolyl)-6-methylpyridine}] (6) is mononuclear exhibiting a distorted octahedral-coordination geometry around the nickel atom. Upon activation with diethylaluminium chloride (Et2AlCl), all the complexes exhibited moderate to good catalytic activity for ethylene oligomerization (27â415 g mmolâ1(Ni) hâ1barâ1) with high selectivity for ethylene dimerization to form α-butene. The observed variance in the catalytic activities of the complexes is attributed to the different ligand environments and effects of reaction parameters.
合成并表征了一系列含有苯并咯唑基吡啶的新镍配合物,采用FT-IR光谱和元素分析进行表征。通过单晶X射线衍射确定了两个代表性配合物的分子结构。配合物[NiCl22-(2-benzoxazolyl)-6-methylpyridine}] (5)为中心对称的双核化合物,具有两个五配位的Ni(II)中心,而配合物[NiCl22-(5-methyl-2-benzoxazolyl)-6-methylpyridine}] (6)为单核化合物,显示出在镍原子周围的扭曲八面体配位几何构型。在用氯化二乙铝(Et2AlCl)激活后,所有配合物在乙烯低聚化反应中表现出中等至良好的催化活性(27–415 g mmol⁻¹(Ni) h⁻¹bar⁻¹),并对乙烯二聚化形成α-丁烯具有高度选择性。配合物的催化活性差异归因于不同的配体环境和反应参数的影响。