Ethylene polymerization catalyzed by dinickel complexes with a double-decker structure
Ethylene polymerization catalyzed by dinickel complexes with a double-decker structure
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DOI：
10.1039/c7py00333a
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发表时间：
2017-08
影响因子：
4.6
通讯作者：
Daisuke Takeuchi;Yuriko Chiba;Shigenaga Takano;Hideo Kurihara;Minoru Kobayashi;K. Osakada
中科院分区：
文献类型：
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作者：
Daisuke Takeuchi;Yuriko Chiba;Shigenaga Takano;Hideo Kurihara;Minoru Kobayashi;K. Osakada
具有包含两个水杨醛亚胺基团的大环配体的双层二镍配合物用作乙烯聚合的催化剂。该配体的两个亚胺氮通过2,3,6,7,9,9-六甲基呫吨-4,5-二基间隔基（1-2H）和2,7-叔丁基-9,9-二甲基呫吨-4,5-二基间隔基（2-2H）连接，形成二镍络合物[Ni2Me2(PMe3)2(1)]和[Ni2Me2(PMe3)2(2)]。 [Ni2Me2(PMe3)2(1)]在室温下的催化活性高于[Ni2Me2(PMe3)2(2)]和单镍配合物[NiMe(PMe3)(1-H)]。所得聚乙烯的 GPC 结果表明，与单镍催化剂 [NiMe(PMe3)(1-H)] 催化的反应 (Mw/Mn = 1.8) 相比，二镍配合物催化的反应产生的聚乙烯具有更宽的分子量分布 (Mw/Mn > 4.0)。 [Ni2Me2(PMe3)2(2)]催化的聚合在60℃下表现出比室温更高的活性。使用 [Ni2Me2(PMe3)2(1)] 和 [Ni2Me2(PMe3)2(2)] 催化剂获得的聚乙烯分为 Tm = 76–77 °C 和更多支化结构（69 和 95 (/1000 C)）的部分和 Tm = 118–120 °C 和较少支化结构（36 和 39 (/1000 C)）的部分。通过单核络合物的聚合不产生对应于较少支化级分的聚乙烯。两个镍中心之间的协同作用导致形成支链较少、分子量较高的结晶聚乙烯。
Double-decker dinickel complexes with a macrocyclic ligand containing two salicylaldimine groups are employed as catalysts for ethylene polymerization. The ligand, whose two imine nitrogens are connected by a 2,3,6,7,9,9-hexamethylxanthene-4,5-diyl spacer (1-2H) and a 2,7-tert-butyl-9,9-dimethylxanthene-4,5-diyl spacer (2-2H), forms dinickel complexes [Ni2Me2(PMe3)2(1)] and [Ni2Me2(PMe3)2(2)]. The catalytic activity of [Ni2Me2(PMe3)2(1)] is higher than those of [Ni2Me2(PMe3)2(2)] and the mononickel complex [NiMe(PMe3)(1-H)] at r.t. The GPC results of the polyethylene obtained suggest that the reaction catalyzed by the dinickel complexes produced polyethylene with a much wider molecular weight distribution (Mw/Mn > 4.0) than that catalyzed by the mononickel catalyst [NiMe(PMe3)(1-H)] (Mw/Mn = 1.8). The polymerization catalyzed by [Ni2Me2(PMe3)2(2)] showed higher activity at 60 °C than at room temperature. Polyethylenes obtained using [Ni2Me2(PMe3)2(1)] and [Ni2Me2(PMe3)2(2)] catalysts were divided into a fraction with Tm = 76–77 °C and a more branched structure (69 and 95 (/1000 C)) and another with Tm = 118–120 °C and a less branched structure (36 and 39 (/1000 C)). Polymerization by the mononuclear complex does not produce the polyethylene corresponding to the less branched fraction. The cooperative effect between the two nickel centers is responsible for the formation of the less branched crystalline polyethylene with a higher molecular weight.