http://eprints.utas.edu.au/4168/ Cocatalyst influence in selective oligomerization: effect on activity, catalyst stability, and 1-Hexane/1-Octene selectivity in the ethylene trimerization and tetramerization reaction McGuinness, DS Rucklidge, AJ Tooze, RP Slawin, AMZ 250102 Chemistry of Catalysis The trimerization and tetramerization of ethylene to 1-hexene and 1-octene with a Cr/PNP/AlEt3 catalyst system, in combination with a variety of cocatalysts, has been investigated. The cocatalysts B(C6F5)3 (1), Al(OC6F5)3 (2), [(Et2O)2H][Al(OC6F5)4] (3), [Ph3C][Ta(OC6F5)6] (4), (Et2O)Al{OCH(C6F5)2}3 (5), (Et2O)- Al{OC(CF3)3}3 (6), [Ph3C][Al{OC(CF3)3}4] (7), [Ph3C][AlF{OC(CF3)3}3] (8), [Ph3C][{(F3C)3CO}3Al- F-Al{OC(CF3)3}3] (9), and [Ph3C][CB11H6Br6] (10) have been evaluated. The relative selectivity to 1-hexene and 1-octene obtained shows a strong dependence on the nature of the cocatalyst, and a range of selectivities from <5% C8 (90% C6) to 72%C8 have been observed. The stability of several cocatalysts toward AlEt3 has been studied, and the poor performance of 1 and 2 is linked to degradation of the cocatalyst through ethyl group exchange with AlEt3. In contrast, the [Al{OC(CF3)3}4]- anion in 7 is much more stable and gives rise to a highly active and longer lived catalyst. The overall productivity and selectivity of the catalyst is dependent upon both cocatalyst stability and the nature of the anion present, and a reason for this effect has been suggested. Selectivity control by the cocatalyst has been ascribed to interaction of the anion with the active Cr center. American Chemical Society 2007 Article PeerReviewed application/pdf http://eprints.utas.edu.au/4168/1/4168.pdf http://dx.doi.org/10.1021/om070029c McGuinness, DS and Rucklidge, AJ and Tooze, RP and Slawin, AMZ (2007) Cocatalyst influence in selective oligomerization: effect on activity, catalyst stability, and 1-Hexane/1-Octene selectivity in the ethylene trimerization and tetramerization reaction. Organometallics, 26 (10). pp. 2561-2569. ISSN 0276-7333 http://eprints.utas.edu.au/4168/http://eprints.utas.edu.au/4168/1/