N-substituted diphosphinoamines:: Toward rational ligand design for the efficient tetramerization of ethylene
N-substituted diphosphinoamines:: Toward rational ligand design for the efficient tetramerization of ethylene
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DOI：
10.1016/j.jcat.2006.10.020
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发表时间：
2007-01-25
影响因子：
7.3
通讯作者：
Wasserscheid, Peter
中科院分区：
文献类型：
--
作者：
Kuhlmann, Sven;Blann, Kevin;Wasserscheid, Peter
合成了具有连接到配体骨架N原子上的不同烷基和环烷基取代基的双（二苯基膦基）胺（PNP）配体，并与铬一起作为乙烯四聚催化剂进行了测试。在用甲基铝氧烷基活化剂活化时，催化剂显示出对1-辛烯和1-己烯的良好活性和选择性，其中最好的配体系统含有环戊基或环己基部分。此外，已经确定，在环己基骨架的2位的取代，更重要的是，在该点的空间体积的增加，导致副产物形成的急剧减少（即，甲基-和亚甲基环戊烷）。有趣的是，在环己基环的6位上的另外的甲基取代将催化剂的选择性从主要的四聚改变为1-己烯和1-辛烯的1：1混合物。结构相似的配体，如环己基甲基和环己基乙基PNP，也进行了测试，也发现产生有效的四聚催化剂。得出的结论是，PNP配体的N-烷基部分的结构微调对于获得有效的四聚催化剂是必不可少的，其中最好的系统实现高达88%（1-辛烯和1-己烯）的组合选择性，具有超过2，000，000 g/（g-Crh）的异常高的活性。(c)2006年爱思唯尔公司All rights reserved.
Bis(diphenylphosphino)amine (PNP) ligands with different alkyl and cycloalkyl substituents attached to the N atom of the ligand backbone were synthesised and tested together with chromium as ethylene tetramerization catalysts. On activation with a methylaluminoxane-based activator, the catalysts displayed good activity and selectivity toward 1-octene and 1-hexene, with the best ligand systems containing cyclopentyl or cyclohexyl moieties. In addition, it was established that substitution at the 2 position of the cyclohexyl skeleton and, more importantly, an increase in steric bulk at that point, led to a drastic reduction of side product formation (i.e., methyl- and methylenecyclopentane). Interestingly, additional methyl substitution in the 6 position of the cyclohexyl ring changed the selectivity of the catalyst from predominantly tetramerization to a 1:1 mixture of 1-hexene and 1-octene. Structurally similar ligands, such as cyclohexylmethyl and cyclohexylethyl PNP, were also tested and were also found to yield efficient tetramerization catalysts. It was concluded that structural fine tuning of the N-alkyl moiety of the PNP ligand is essential for obtaining efficient tetramerization catalysts, with the best systems achieving combined selectivities as high as 88% (1-octene and 1-hexene) with exceptionally high activities exceeding 2,000,000 g/(g-Crh). (c) 2006 Elsevier Inc. All rights reserved.