Chain Transfer to Toluene in Styrene Coordination Polymerization

The chain‐transfer reaction is rather important in coordination polymerization regarding catalytic efficiency, adjustment of molecular weight, and control of chain structure. To date, chain transfer to H2 and Al, Mg, and Zn alkyl compounds and β‐H elimination are the commonly encountered modes. Now...

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Bibliographic Details
Published in:Angewandte Chemie 2020-03, Vol.132 (11), p.4354-4358
Main Authors: Lin, Fei, Liu, Zhaohe, Wang, Meiyan, Liu, Bo, Li, Shihui, Cui, Dongmei
Format: Article
Language:English
Subjects:
Alkyl compounds
Aluminum
C-H-Aktivierung
Chain transfer
Chains (polymeric)
Chemistry
Coordination
Fluorine
Kettentransfer
Koordinationspolymerisation
Ligands
Magnesium
Molecular structure
Molecular weight
NMR
Nuclear magnetic resonance
Polymerization
Seltene Erden
Styrene
Styrenes
Styrol-Polymerisation
Toluene
Two dimensional analysis
Zinc
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Summary:The chain‐transfer reaction is rather important in coordination polymerization regarding catalytic efficiency, adjustment of molecular weight, and control of chain structure. To date, chain transfer to H2 and Al, Mg, and Zn alkyl compounds and β‐H elimination are the commonly encountered modes. Now a novel chain transfer to toluene is reported. By introducing fluorine atoms into the β‐diketimine ligands, an inert catalytic system for styrene (St) coordination polymerization was transferred into the highly active one. The activity increased with an increase in the number of fluorines in the ligands. Surprisingly, the molecular weights of resultant polystyrenes are very low (Mn=2000–6600 Da) despite of St loadings, corresponding up to 121 chains per active species. The mechanisms were investigated by DFT simulation, MALDI‐TOF MS, isotope tracing experiment and 2D NMR spectrum analyses, which revealed that the fluorine activated the polymerization and directed chain transfer to toluene. Wechsel der Kette: Der hoch effiziente Kettentransfer zu Toluol wurde erstmalig in Styrol‐Koordinationspolymerisation durch Nutzung von Seltenerdmetall‐Vorläufern erreicht. Die höhere Polymerisationsaktivität wird den Fluor‐Substituenten an den β‐Diiminato‐Liganden zugeordnet, die die LUMO‐Energie des aktiven Metallzentrums absenken und den Kettentransfer zum ortho‐Proton von Toluol dirigieren.
ISSN:0044-8249
1521-3757
DOI:10.1002/ange.201914603