Chromium-catalysed ethene trimerisation and tetramerisation—breaking the rules in olefin oligomerisation

Abstract

The discovery of a new generation of highly active and selective ethene trimerisation and tetramerisation catalysts has radically changed the field of olefin oligomerisation. This Frontiers article gives an overview of these recent advances.

A survey of pendant donor-functionalised (N,O) phosphine ligands for Cr-catalysed ethylene tri- and tetramerisation

“…A number of such technologies have been reported in both the patent and academic literature and have been the focus of a number of reviews in recent years. [1][2][3][4][5][6][7] Investigation of the mechanistic aspects of this reaction also continues to receive interest. [8][9][10][11] While a number of systems are known for the selective trimerisation of ethylene to 1-hexene, there are fewer known systems with high activity and selectivity for ethylene tetramerisation.…”

Distinguishing Chain Growth Mechanisms in Metal-catalyzed Olefin Oligomerization and Polymerization Systems: C2H4/C2D4 Co-oligomerization/Polymerization Experiments Using Chromium, Iron, and Cobalt Catalysts

“…trimerization and tetramerization to give 1-hexene and 1-octene constitute another milestone in this area. [10][11][12][13] A detailed understanding of the chain growth mechanism in olefin polymerization is of immense practical importance because many polymer properties are related to the microstructure of the polymer, which in turn is controlled by the catalyst. Important elementary reaction steps in transition metal catalyzed oligomerization and polymerization reactions of olefins are propagation (k p ) and termination (k t ).…”

“…16 Here, oxidative coupling of two coordinated ethylene molecules at a metal centre form a metallacyclopentane, which upon further insertions can grow to a metallacycloheptane and so on. 12,13 Subsequent release of the product proceeds either via a sequential β-H eliminationreductive elimination process or alternatively through a concerted [3,ω]-hydrogen shift. 17 With certain chromium catalysts higher molecular weight oligomers can be obtained via this mechanism.…”

Insights in the mechanism of selective olefin oligomerisation catalysis using stopped-flow freeze-quench techniques: A Mo K-edge QEXAFS study

“…1,2 However, the selective trimerisation and tetramerisation of ethene to produce the linear alpha-olefins (LAOs) 1-hexene and 1-octene respectively are of major significance due to the importance of these co-monomers in the production of linear low-density polyethylene (LLDPE). 2,3,4 LLDPE accounts for around 50% of the LAO co-monomers produced industrially. A variety of transition metal catalysts facilitate the selective trimerisation of ethene, most of which are based on early transition metals such as titanium, tantalum or, most importantly, chromium.…”

“…A variety of transition metal catalysts facilitate the selective trimerisation of ethene, most of which are based on early transition metals such as titanium, tantalum or, most importantly, chromium. 2,3,4 These form the basis of several key industrial catalysts, including the Phillips pyrrolide system, the Sasol mixed heteroatom systems and the BP diphosphine systems. 5,6,7 The extremely high selectivity for 1-hexene is thought to occur via a mechanism based upon a metallocyclic intermediate formed through reaction of Cr(III) pre-catalysts with ethene in the presence of methylaluminoxane (MAO) co-catalyst.…”