New tetradentate N,N,N,N-chelating α-diimine ligands and their corresponding zinc and nickel complexes: synthesis, characterisation and testing as olefin polymerisation catalysts
作者:Lidong Li、Clara S. B. Gomes、Pedro T. Gomes、M. Teresa Duarte、Zhiqiang Fan
DOI:10.1039/c0dt01308k
日期:——
A series of zinc complexes of the general formula [ZnCl(ArNC(An)âC(An)NAr)]+}2[Zn2Cl6]2â (where Ar = 2-(1-benzyl-1H-1,2,3-triazol-4-yl)phenyl 2a, 2-(1-(1-phenylethyl)-1H-1,2,3-triazol-4-yl)phenyl 2b, 2-(1-phenyl-1H-1,2,3-triazol-4-yl)phenyl 2c; An = acenaphthene backbone) were prepared by the condensation of acenaphthenequinone with the corresponding o-triazolyl-substituted anilines (2-(1-benzyl-1H-1,2,3-triazol-4-yl)aniline 1a, 2-(1-(1-phenylethyl)-1H-1,2,3-triazol-4-yl)aniline 1b, 2-(1-phenyl-1H-1,2,3-triazol-4-yl)aniline 1c) which were formed by the copper(I)-catalyzed Huisgen[3+2] dipolar cycloaddition between 2-ethynylaniline and the corresponding azides in high yields, using anhydrous ZnCl2 as the metal template, in boiling glacial acetic acid. Zinc complexes of the type [ZnCl(ArNC(An)âC(An)NAr)]+[ZnCl3(NCCH3)]â (4aâc) were synthesized by crystallisation of the corresponding complexes 2aâc in acetonitrile, at â20 °C. After removal of zinc dichloride from complexes 2aâc by the addition of potassium oxalate, in dichloromethane, the tetradentate N,N,N,N-chelating α-diimine ligands of the type ArNC(An)âC(An)NAr (5aâc) were obtained. The new ligand precursors and zinc complexes were characterised by elemental analysis, 1H and 13C1H} NMR spectroscopy, two-dimensional NMR spectroscopy, and X-ray diffraction. Reaction of the ligand precursors 5aâc with [NiBr2(DME)], in dichloromethane, gave nickel complexes of the type [NiBr2(ArNC(An)âC(An)NAr)] (6aâc). The results of single crystal X-ray diffraction characterisation and magnetic susceptibility measurements demonstrated that nickel complexes 6aâc possess octahedral geometries around the nickel atoms with variable configurations, the Br atoms of which can be ionized when dissolved in methanol. In preliminary catalytic tests, complexes 6aâc revealed to be active as catalysts for the polymerisation of norbornene and styrene, when activated by cocatalyst MAO. The characterisation of the polymers by 1H and 13C1H} NMR spectroscopy, gel permeation chromatography/size-exclusion chromatography (GPC/SEC) revealed that these polymers were formed by a coordination addition mechanism.
一系列通式为[ZnCl(ArNC(An)âC(An)NAr)]+}2[Zn2Cl6]2â的锌配合物(其中 Ar = 2-(1-苄基-1H-1,2,3-三唑-4-基)苯基 2a,2-(1-(1-苯基乙基)-1H-1,2,3-三唑-4-基)苯基 2b,2-(1-苯基-1H-1,2,3-三唑-4-基)苯基 2c;An = 苊骨架)通过苊醌与相应的邻三唑基取代苯胺(2-(1-苄基-1H-1,2,3-三唑-4-基)苯胺 1a、2-(1-(1-苯基乙基)-1H-1,2,3-三唑-4-基)苯胺 1b、2-(1-苯基-1H-1,2,3-三唑-4-基)苯基 2c)缩合制备、1b)、2-(1-苯基-1H-1,2,3-三唑-4-基)苯胺 1c),它们是以无水 ZnCl2 为金属模板,在沸腾的冰醋酸中,通过铜(I)催化的 Huisgen[3+2] 二极环加成反应,在 2-乙炔基苯胺和相应的叠氮化物之间高产率地形成的。相应的络合物 2aâc 在 20°C 的乙腈中结晶,合成了[ZnCl(ArNC(An)âC(An)NAr)]+[ZnCl3(NCCH3)]â(4aâc)类型的锌络合物。在二氯甲烷中加入草酸钾去除络合物 2aâc 中的二氯化锌后,得到了 ArNC(An)âC(An)NAr(5aâc)类型的四价 N,N,N,N,N-螯合δ-二亚胺配体。通过元素分析、1H 和 13C1H} 核磁共振波谱、二相色谱和二相色谱分析,对新配体前体和锌配合物进行了表征。核磁共振光谱、二维核磁共振光谱和 X 射线衍射表征。配体前体 5aâc 与[NiBr2(DME)]在二氯甲烷中反应,得到[NiBr2(ArNC(An)âC(An)NAr)]类型的镍配合物(6aâc)。单晶 X 射线衍射表征和磁感应强度测量结果表明,镍络合物 6aâc 具有围绕镍原子的八面体几何结构,其构型可变,当溶解在甲醇中时,其中的 Br 原子可以电离。在初步催化测试中,络合物 6aâc 被助催化剂 MAO 活化后,显示出作为降冰片烯和苯乙烯聚合催化剂的活性。通过 1H 和 13C1H} NMR 光谱、凝胶渗透分析、聚合反应测试和催化测试,对聚合物进行了表征。核磁共振光谱、凝胶渗透色谱法/尺寸排阻色谱法(GPC/SEC)对聚合物的表征表明,这些聚合物是通过配位加成机制形成的。