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The Effect of Substituents in PNPNH Ligands on Activity and Selectivity of a Chromium‐Based Catalyst System for Highly Selective Ethylene Trimerization
Author(s) -
Heinig Stefan,
Wöhl Anina,
Müller Wolfgang,
AlHazmi Mohammed H.,
Müller Bernd H.,
Peulecke Normen,
Rosenthal Uwe
Publication year - 2013
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201300324
Subject(s) - chemistry , ethylene , catalysis , ligand (biochemistry) , selectivity , steric effects , substituent , chromium , polymer chemistry , photochemistry , medicinal chemistry , stereochemistry , organic chemistry , biochemistry , receptor
The influence of ligand substituents on a highly selective homogeneous catalyst system for the trimerization of ethylene to 1‐hexene consisting of chromium(III) acetylacetonate, a ligand with a PNPNH backbone, tetraphenylphosphonium chloride as chlorine source, and triethyl aluminum as activator was investigated. These N‐modified and P‐modified ligands, which differ strongly in their electronic and steric properties of the substituents, were tested in the ethylene trimerization at three temperatures (50, 70, and 90 °C). Interestingly, the substituents at the N atoms of the PNPNH‐backbone had only little effect on the catalytic activity, on 1‐hexene selectivity, and on thermal stability of the catalyst system, whereas the substituents at the P atoms significantly influenced the efficiency of the system. This is even more surprising as the PNP ligand from SASOL for ethylene tetramerization is much more sensitive against substituent variation at its N atom.