Ethylene Tri- and Tetramerization: a Steric Parameter Selectivity Switch from X‑ray Crystallography and Computational Analysis

A steric parameter (θN‑sub) is
introduced to describe the steric bulk at the nitrogen atom on a range
of PNP ligands used in ethylene tri- and tetramerization. This parameter
was calculated for the free ligands and different metal complexes
thereof and compared to catalytic data. A specific tendency is observed
for the value of θN‑sub and 1-hexene selectivity,
and a slight increase in 1-octene selectivity is found with increased
bulkiness of the substituents on the nitrogen atom.

本研究引入空间位阻参数（steric parameter）θ_N-sub，用于描述一系列应用于乙烯三聚与四聚反应的PNP配体中氮原子位点的空间位阻体积。该参数针对游离配体及其各类金属配合物完成计算，并与催化实验数据开展对比分析。研究发现，θ_N-sub的数值与1-己烯选择性之间存在特定关联趋势；同时，随着氮原子上取代基的空间位阻增大，1-辛烯选择性呈现小幅提升的变化规律。