Urciuoli Gaia, Zaccaria Francesco, Zuccaccia Cristiano, Cipullo Roberta, Budzelaar Peter H M, Vittoria Antonio, Ehm Christian, Macchioni Alceo, Busico Vincenzo
Department of Chemical Sciences, Federico II University of Naples, via Cinthia, 80126 Napoli, Italy.
Department of Chemistry, Biology and Biotechnology and CIRCC, University of Perugia, via Elce di Sotto 8, 06123 Perugia, Italy.
Dalton Trans. 2024 Jan 30;53(5):2286-2293. doi: 10.1039/d3dt04081j.
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 -symmetric (Hf-CS-Met) and -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(PhNMe)Al}[B(CF)] (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 ( 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.
用于烯烃聚合的铪催化剂通常对助催化剂的性质非常敏感，特别是当助催化剂含有“游离”三烷基铝时。本文研究了四种铪催化剂在铪催化丙烯聚合反应中的助催化剂效应，这四种催化剂分别属于对称（Hf-CS-Met）和非对称（Hf-C2-Met）茂金属家族，以及八面体（Hf-OOOO）和五配位（Hf-PyAm）“后茂金属”。将最近开发的{iBu(PhNMe)Al}[B(CF)]（AlHAl）助催化剂的性能与甲基铝氧烷、苯酚改性甲基铝氧烷和三苯基硼酸酯/三异丁基铝等成熟体系的性能进行了比较。使用甲基铝氧烷时观察到最差的催化性能。相反，最佳助催化剂因所使用的铪催化剂和感兴趣的性能指标而异，这突出了选择合适的预催化剂/助催化剂组合的复杂性和重要性。AlHAl被证明是所有测试催化剂的合适体系，在某些情况下，就生产率而言（对于铪茂金属）它具有最佳性能。此外，它通常能得到高分子量的聚合物，对于像Hf-PyAm这样能使链容易转移到铝上的催化剂也是如此。这表明AlHAl与阳离子活性物种形成异双核加合物的倾向较低，因此可防止通过链转移到铝上形成休眠位点和/或终止事件。
