| Autor: |
Urciuoli G; Department of Chemical Sciences, Federico II University of Naples, via Cinthia, 80126 Napoli, Italy. francesco.zaccaria@unina.it.; Department of Chemistry, Biology and Biotechnology and CIRCC, University of Perugia, via Elce di Sotto 8, 06123 Perugia, Italy. cristiano.zuccaccia@unipg.it.; DPI, P.O. Box 902, 5600 AX Eindhoven, the Netherlands., Zaccaria F; Department of Chemical Sciences, Federico II University of Naples, via Cinthia, 80126 Napoli, Italy. francesco.zaccaria@unina.it.; DPI, P.O. Box 902, 5600 AX Eindhoven, the Netherlands., Zuccaccia C; Department of Chemistry, Biology and Biotechnology and CIRCC, University of Perugia, via Elce di Sotto 8, 06123 Perugia, Italy. cristiano.zuccaccia@unipg.it.; DPI, P.O. Box 902, 5600 AX Eindhoven, the Netherlands., Cipullo R; Department of Chemical Sciences, Federico II University of Naples, via Cinthia, 80126 Napoli, Italy. francesco.zaccaria@unina.it.; DPI, P.O. Box 902, 5600 AX Eindhoven, the Netherlands., Budzelaar PHM; Department of Chemical Sciences, Federico II University of Naples, via Cinthia, 80126 Napoli, Italy. francesco.zaccaria@unina.it., Vittoria A; Department of Chemical Sciences, Federico II University of Naples, via Cinthia, 80126 Napoli, Italy. francesco.zaccaria@unina.it., Ehm C; Department of Chemical Sciences, Federico II University of Naples, via Cinthia, 80126 Napoli, Italy. francesco.zaccaria@unina.it.; DPI, P.O. Box 902, 5600 AX Eindhoven, the Netherlands., Macchioni A; Department of Chemistry, Biology and Biotechnology and CIRCC, University of Perugia, via Elce di Sotto 8, 06123 Perugia, Italy. cristiano.zuccaccia@unipg.it.; DPI, P.O. Box 902, 5600 AX Eindhoven, the Netherlands., Busico V; Department of Chemical Sciences, Federico II University of Naples, via Cinthia, 80126 Napoli, Italy. francesco.zaccaria@unina.it.; DPI, P.O. Box 902, 5600 AX Eindhoven, the Netherlands. |
| Abstrakt: |
Hafnium catalysts for olefin polymerization are often very sensitive to the nature of cocatalysts, especially if they contain "free" aluminium trialkyls. Herein, cocatalyst effects in Hf-catalysed propene polymerization are examined for four Hf catalysts belonging to the family of C S -symmetric (Hf-CS-Met) and C 2 -symmetric (Hf-C2-Met) metallocenes, as well as of octahedral (Hf-OOOO) and pentacoordinated (Hf-PyAm) "post-metallocenes". The performance of the recently developed {[iBu 2 (PhNMe 2 )Al] 2 (μ-H)} + [B(C 6 F 5 ) 4 ] - (AlHAl) cocatalyst is compared with that of established systems like methylalumoxane, phenol-modified methylalumoxane and trityl borate/tri-iso-butylaluminium. The worst catalytic performance is observed with MAO. Conversely, the best cocatalyst varies depending on the Hf catalyst used and the performance indicator of interest, highlighting the complexity and importance of selecting the right precatalyst/cocatalyst combination. AlHAl proved to be a suitable system for all catalysts tested and, in some cases, it provides the best performance in terms of productivity ( e.g. with hafnocenes). Furthermore, it generally leads to high molecular weight polymers, also with catalysts enabling easy chain transfer to Al like Hf-PyAm. This suggests that AlHAl has a low tendency to form heterodinuclear adducts with the cationic active species, therefore preventing the formation of dormant sites and/or termination events by chain transfer to Al. |
