Dinickel Bisphenoxyiminato Complexes for the Polymerization of Ethylene and α-Olefins.
Dinickel Bisphenoxyiminato Complexes for the Polymerization of Ethylene and α-Olefins.
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DOI：
10.1021/om2011694
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发表时间：
2012-03-26
期刊：
影响因子：
2.8
通讯作者：
Agapie T
中科院分区：
文献类型：
--
作者：
Radlauer M;Day MW;Agapie T
报道了一种基于刚性对三联苯骨架的双核镍苯氧亚氨基烯烃聚合催化剂。三联苯单元的中心芳烃的全甲基化和芳基-芳基键邻位的外围环的氧取代阻止了围绕这些键的旋转，允许分离配体的阻转异构体。合成了相应的顺式和反式二镍配合物（25-s和25-a），并用X-射线单晶衍射对其结构进行了表征。这些框架限制了金属中心的相对运动，从而限制了金属-金属距离。配体前体（7-a）异构化的动力学研究允许计算异构化过程的活化参数（ΔH = 28.0 ± 0.4 kcal×mol−1和ΔS = −12.3 ± 0.4 cal×mol−1×K−1）。所报道的镍配合物对乙烯聚合[TOF高达3700（mol C2 H4）×（mol Ni）−1×h−1]和乙烯/α-烯烃共聚具有活性。在乙烯的聚合中仅观察到甲基支链，而α-烯烃在没有明显的链行走的情况下被引入。这些催化剂在极性添加剂存在下和纯四氢呋喃中具有活性。顺式和反式异构体在聚合活性和聚合物支化度和分子量方面不同。为了比较，制备并研究了一系列单核镍配合物（26，27-s，27-a，28，30）。讨论了催化剂的结构和核性对反应性的影响。
Dinuclear nickelphenoxyiminato olefin polymerization catalysts based on rigid p-terphenyl frameworks are reported. Permethylation of the central arene of the terphenyl unit and oxygen substitution of the peripheral rings ortho to the aryl-aryl linkages blocks rotation around these linkages allowing atropisomers of the ligand to be isolated. The corresponding syn and anti dinickel complexes (25-s and 25-a) were synthesized and characterized by single crystal X-ray diffraction. These frameworks limit the relative movement of the metal centers restricting the metal-metal distance. Kinetics studies of isomerization of a ligand precursor (7-a) allowed the calculation of the activation parameters for the isomerization process (ΔH‡ = 28.0 ± 0.4 kcal×mol−1 and ΔS‡ = −12.3 ± 0.4 cal×mol−1×K−1). The reported nickel complexes are active for ethylene polymerization [TOF up to 3700 (mol C2H4)×(mol Ni)−1×h−1] and ethylene/α-olefin copolymerization. Only methyl branches are observed in the polymerization of ethylene, while α-olefins are incorporated without apparent chain walking. These catalysts are active in the presence of polar additives and in neat tetrahydrofuran. The syn and anti isomers differ in polymerization activity and polymer degree of branching and molecular weight. For comparison, a series of mononuclear nickel complexes (26, 27-s, 27-a, 28, 30) was prepared and studied. The effects of structure and catalyst nuclearity on reactivity are discussed.
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