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首页> 外文期刊>Chemistry: A European journal >Neutral nickel oligo- and polymerization catalysts: The importance of alkyl phosphine intermediates in chain termination
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Neutral nickel oligo- and polymerization catalysts: The importance of alkyl phosphine intermediates in chain termination

机译：中性镍低聚和聚合催化剂：烷基膦中间体在链终止中的重要性

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摘要

An unconventional chain termination reaction has been explored for the SHOP (Shell higher olefin process)-type, anilinotropone, and salicylaldiminato nickel-based oligo- and polymerization catalysts by using density functional theory (DFT). Starting from the tetracoordinate alkyl phosphine complex, the termination reaction was found to involve a rearrangement of the alkyl chain to form a pentacoordinate β-agostic complex, β-hydride elimination, and olefinic chain dissociation and to compete with propagation at sufficiently high phosphine concentration and/or basicity. It provides the first complete and convincing mechanistic rationale for the decreasing chain lengths observed upon increasing phosphine concentration and basicity. The unconventional reaction was found to be a major termination pathway for the SHOP-type catalyst and is very unlikely to lead to branching and olefin isomerization, which is critical for explaining why the SHOP catalyst, in contrast to the anilinotropone and salicylaldiminato catalysts, tends to lead to the oligomerization of ethylene to form linear α-olefins. Based on our results we have proposed a new and extended catalytic cycle for the SHOP-type ethylene oligomerization catalyst. Finally, the importance of the new termination reaction for the SHOP-type catalyst suggests that this reaction may also operate with other ethylene oligomerization nickel catalysts. This prediction was confirmed for a pyrazolonatophosphine catalyst, for which the new termination route was found to be even more facile, which explains the short oligomers produced by this catalyst.
机译：通过使用密度泛函理论（DFT），对SHOP（壳高级烯烃工艺）型，苯胺托酮和水杨基亚胺基镍基低聚和聚合催化剂进行了非常规链终止反应的研究。从四配位的烷基膦配合物开始，发现终止反应涉及烷基链的重排以形成五配位的β-声波配合物，β-氢化物消除和烯烃链解离，并在足够高的膦浓度下竞争扩散。 /或基本性。它提供了第一个完整且令人信服的机理原理，以解决因磷化氢浓度和碱度提高而观察到的链长减少的问题。发现非常规反应是SHOP型催化剂的主要终止途径，并且极不可能导致支化和烯烃异构化，这对于解释为什么SHOP催化剂与苯并萘醌和水杨基亚胺基化催化剂相比趋向于是至关重要的。导致乙烯低聚形成线性α-烯烃。根据我们的结果，我们为SHOP型乙烯低聚催化剂提出了新的延长的催化循环。最后，新的终止反应对SHOP型催化剂的重要性表明该反应也可与其他乙烯低聚镍催化剂一起使用。吡唑并酮膦催化剂的这一预测得到了证实，对于该催化剂而言，发现新的终止途径更加容易，这解释了该催化剂产生的短低聚物。

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