Suppression of Chain Transfer via Restricted Rotation Effect of Dibenzosuberyl Substituents in Polymerization Catalysis

2021 ◽  
Author(s):  
Shengyu Dai ◽  
Gen Li ◽  
Weiqing Lu ◽  
Yudan Liao ◽  
Weigang Fan
Keyword(s):  
Chain Transfer ◽  
Olefin Polymerization ◽  
Effective Strategy ◽  
Rotation Effect ◽  
Restricted Rotation ◽  
Polymerization Catalysis

The introduction of bulky ortho-steric substituents into α-diimine Ni(II) and Pd(II) species has been often used as an effective strategy to retard the chain transfer in olefin polymerization. In this...

scholarly journals Chain Transfer to Solvent and Monomer in Early Transition Metal Catalyzed Olefin Polymerization: Mechanisms and Implications for Catalysis

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 215
Author(s):  
Francesco Zaccaria ◽  
Peter H. M. Budzelaar ◽  
Cristiano Zuccaccia ◽  
Roberta Cipullo ◽  
Alceo Macchioni ◽  
...  
Keyword(s):  
Transition Metal ◽  
Chain Transfer ◽  
Olefin Polymerization ◽  
Transfer Reactions ◽  
Organic Radical ◽  
Mechanistic Studies ◽  
Early Transition Metal ◽  
Polymerization Catalysis ◽  
Insertion Polymerization ◽  
Early Transition

Even after several decades of intense research, mechanistic studies of olefin polymerization by early transition metal catalysts continue to reveal unexpected elementary reaction steps. In this mini-review, the recent discovery of two unprecedented chain termination processes is summarized: chain transfer to solvent (CTS) and chain transfer to monomer (CTM), leading to benzyl/tolyl and allyl type chain ends, respectively. Although similar transfer reactions are well-known in radical polymerization, only very recently they have been observed also in olefin insertion polymerization catalysis. In the latter context, these processes were first identified in Ti-catalyzed propene and ethene polymerization; more recently, CTS was also reported in Sc-catalyzed styrene polymerization. In the Ti case, these processes represent a unique combination of insertion polymerization, organic radical chemistry and reactivity of a M(IV)/M(III) redox couple. In the Sc case, CTS occurs via a σ-bond metathesis reactivity, and it is associated with a significant boost of catalytic activity and/or with tuning of polystyrene molecular weight and tacticity. The mechanistic studies that led to the understanding of these chain transfer reactions are summarized, highlighting their relevance in olefin polymerization catalysis and beyond.

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