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Oligomerisation of Ethylene to Linear α‐Olefins by new C s ‐ and C 1 ‐Symmetric [2,6‐Bis(imino)pyridyl]iron and ‐cobalt Dichloride Complexes
Author(s) -
Bianchini Claudio,
Mantovani Giuseppe,
Meli Andrea,
Migliacci Fabio,
Zanobini Fabrizio,
Laschi Franco,
Sommazzi Anna
Publication year - 2003
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200390213
Subject(s) - chemistry , methylaluminoxane , ethylene , catalysis , cobalt , substituent , alkyl , crystallography , square pyramidal molecular geometry , metal , polymer chemistry , aryl , medicinal chemistry , crystal structure , stereochemistry , inorganic chemistry , metallocene , organic chemistry , polymerization , polymer
Abstract A new family of C s ‐ and C 1 ‐symmetric 2,6‐bis(imino)pyridyl ligands has been synthesised. These ligands, which differ from their known counterparts in the contemporaneous presence of alkyl and aryl substituent at the ketimine nitrogen atoms, form stable, five‐coordinate complexes with FeCl 2 and CoCl 2 . All ligands and catalysts have been fully characterised both in the solid state and in solution. A single‐crystal X‐ray analysis of [CoCl 2 {2‐[CMe=N−(2,6‐dimethylphenyl)]‐6‐(CMe=N−C 6 H 11 )C 5 H 3 N}]·H 2 O shows the metal centre to adopt a highly distorted square‐pyramidal geometry. In combination with methylaluminoxane (MAO), both iron and cobalt compounds act as effective and selective (> 99%) catalysts for the oligomerisation of ethylene to a Schulz−Flory distribution of α‐olefins, with the α factor ranging from 0.61 to 0.91. The iron catalysts exhibit TOFs as high as 7·10 5 mol C 2 H 4 (mol of cat × h) −1 and are much more active than their cobalt analogues. Experiments at different ethylene pressures with the iron catalysts showed that both the propagation rate and the chain transfer rate are first order in ethylene pressure. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2003)