4168 17 archive 337 disk0/00/00/41/68 2008-04-07 14:25:42 2008-11-18 00:32:53 2008-07-16 17:05:18 article show David.McGuinness@utas.edu.au McGuinness DS David.McGuinness@utas.edu.au Rucklidge AJ Tooze RP Slawin AMZ pub 030601 250102 860604 670706 restricted Copyright © 2007 American Chemical Society category => A1 categoryDesc => Refereed Article in a Scholarly Journal eprintID => 0 field1 => Organometallics field10 => field11 => field12 => field13 => field2 => Washington field3 => 26 field4 => 10 field5 => 2561-2569 field6 => American Chemical Society field7 => 0276-7333 field8 => field9 => funding => Y grant => lastUpdate => 12/03/2008 rfcd => 250102 seo => 670706 themeArea => FT title => "Cocatalyst Influence in Selective Oligomerization: Effect on Activity, Catalyst Stability, and 1-Hexane/1-Octene Selectivity in the Ethylene Trimerization and Tetramerization Reaction" tor => AR uid => 50974 update => no 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. 2007 published Organometallics 26 10 American Chemical Society 2561-2569 10.1021/om070029c TRUE 0276-7333 http://dx.doi.org/10.1021/om070029c 4809 3 4168 1 application/pdf en staffonly cc_utas

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