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Ethylene Tetramerisation: A Structure‐Selectivity Correlation
Author(s) -
Makume Boitumelo F.,
Holzapfel Cedric W.,
Maumela Munaka C.,
Willemse J. Alexander,
Berg Jan A.
Publication year - 2020
Publication title -
chempluschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.801
H-Index - 61
ISSN - 2192-6506
DOI - 10.1002/cplu.202000553
Subject(s) - selectivity , steric effects , ligand (biochemistry) , chemistry , ethylene , cationic polymerization , substituent , catalysis , stereochemistry , organic chemistry , biochemistry , receptor
The effect of ethylene tetramerisation ligand structures on 1‐octene selectivity is well studied. However, by‐product formation is less understood. In this work, a range of PNP ligand structures are correlated with the full product selectivity and with catalyst activity. As steric bulk on the N‐substituent increases, the product selectivity shifts from >10 % to < 3% of both C6 cyclics and C16+ by‐products. 1‐Octene peaks at ca. 70%. Thereafter, only 1‐hexene increases. Similar selectivity changes were observed for ortho ‐Ph‐substituted PNP ligands. The C10‐14 selectivity was less affected by the ligand structure. The ligand effect on the changes in selectivity is explained mechanistically. Lastly, an increase in ligand steric bulk was found to improve catalyst activity and reduce polymer formation by an order of magnitude. It is proposed that steric bulk promotes formation of cationic catalytic species which are responsible for selective ethylene oligomerisation.