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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >'Dormant' secondary metal-alkyl complexes are not omnipresent
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'Dormant' secondary metal-alkyl complexes are not omnipresent

机译：“休眠”仲金属-烷基络合物不存在

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摘要

This theoretical study was inspired by the perpetual debate over the so-called "dormancy" of the active sites in propylene polymerization, i.e., a drop in their activity after a regioerror (2,1-insertion), which was reported to occur in many (although not all) catalytic systems. To explore the range of possible situations, we have selected two homogeneous systems of fundamentally different structure: an octahedral system Of C-2 symmetry with a tetradentate -O-N-N-O- ligand and a bridged indenyl catalyst. This choice was not accidental; it is in these two systems where the experimentalists cannot reach a consensus about dormancy. Our density-functional theory calculations explain why in certain catalytic systems both primary and secondary alkyl complexes can be equally reactive toward propylene polymerization, despite the intuitive concept of dormancy. To understand such a behavior, it was imperative to build an extensive model, including the counteranion and solvent effects. The discussion is also supplemented by our latest calculations on the classical second-generation Ziegler-Natta system.
机译：这项理论研究的灵感源于对丙烯聚合反应中活性位点所谓“休眠”的长期争论，即，在发生区域错误（2,1-插入）后，其活性下降，据报道许多情况下都发生了这种现象。 （尽管不是全部）催化系统。为了探索可能的情况范围，我们选择了两个基本不同结构的均相系统：一个具有四齿-O-N-N-O-配体的C-2对称八面体系统和一个桥联的茚基催化剂。这个选择不是偶然的。在这两个系统中，实验者无法就休眠问题达成共识。我们的密度泛函理论计算解释了为什么在某些催化体系中，尽管具有直观的休眠概念，伯烷基和仲烷基络合物对丙烯聚合反应都具有同等反应性。要了解这种行为，必须建立一个广泛的模型，包括抗衡阴离子和溶剂效应。我们对经典第二代Ziegler-Natta系统的最新计算也对讨论进行了补充。

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