title: Mechanistic investigations of the ethylene tetramerisation reaction.
abstract: The unprecedented selective tetramerisation of ethylene to 1-octene was recently reported. In the present study various mechanistic aspects of this novel transformation were investigated. The unusually high 1-octene selectivity in chromium-catalyzed ethylene tetramerisation reactions is caused by the unique extended metallacyclic mechanism in operation. Both 1-octene and higher 1-alkenes are formed by further ethylene insertion into a metallacycloheptane intermediate, whereas 1-hexene is formed by elimination from this species as in other reported trimerisation reactions. This is supported by deuterium labeling studies, analysis of the molar distribution of 1-alkene products, and identification of secondary co-oligomerization reaction products. In addition, the formation of two C6 cyclic products, methylenecyclopentane and methylcyclopentane, is discussed, and a bimetallic disproportionation mechanism to account for the available data is proposed.
authors.affiliation: Sasol Technology (Pty) Ltd, R&D Division, 1 Klasie Havenga Road, Sasolburg 1947, South Africa. Matthew.Overett@Sasol.com
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Overett
authors.forename: Kevin
authors.initials: K
authors.lastname: Blann
authors.forename: Annette
authors.initials: A
authors.lastname: Bollmann
authors.forename: John T
authors.initials: JT
authors.lastname: Dixon
authors.forename: Daleen
authors.initials: D
authors.lastname: Haasbroek
authors.forename: Esna
authors.initials: E
authors.lastname: Killian
authors.forename: Hulisani
authors.initials: H
authors.lastname: Maumela
authors.forename: David S
authors.initials: DS
authors.lastname: McGuinness
authors.forename: David H
authors.initials: DH
authors.lastname: Morgan