Influences of Alkyl and Aryl Substituents on Iminopyridine Fe(II)- and Co(II)-Catalyzed Isoprene Polymerization.

Lihua Guo,Shuoyan Xiong,Zhe Liu,Wenjing Liu,Changle Chen,Yanlan Liu,Xinyu Jing

doi:10.3390/polym8110389

Abstract

A series of alkyl- and aryl-substituted iminopyridine Fe(II) complexes 1a–7a and Co(II) complexes 2b, 3b, 5b, and 6b were synthesized. The activator effect, influence of temperature, and, particularly, the alkyl and aryl substituents’ effect on catalytic activity, polymer molecular weight, and regio-/stereoselectivity were investigated when these complexes were applied in isoprene polymerization. All of the Fe(II) complexes afforded polyisoprene with high molecular weight and moderate cis-1,4 selectivity. In contrast, the Co(II) complexes produced polymers with low molecular weight and relatively high cis-1,4 selectivity. In the iminopyridine Fe(II) system, the alkyl and aryl substituents’ effect exhibits significant variation on the isoprene polymerization. In the iminopyridine Co(II) system, there is little influence observed on isoprene polymerization by alkyl and aryl substituents.

Highlights

The polymerization of isoprene can afford polymers with various regio- and/or stereoregularities such as isotactic or syndiotactic polyisoprene via 1,2 or 3,4 addition, and cis- or trans-1,4 polyisoprene via 1,4 addition
Cyclohexyl(pyridin-2-yl-methylene)amine (L1): the reaction mixture was concentrated under reduced pressure
Adamantyl(pyridin-2-yl-methylene)amine (L3): the reaction mixture was concentrated under reduced pressure

Summary

Introduction

The polymerization of isoprene can afford polymers with various regio- and/or stereoregularities such as isotactic or syndiotactic polyisoprene via 1,2 or 3,4 addition, and cis- or trans-1,4 polyisoprene via 1,4 addition. Titanium and rare-earth metal catalysts can afford cis-1,4 and trans-1,4 polybutadienes and polyisoprenes with up to 98% selectivity [4,5,6,7,8,9,10,11,12,13,14,15]. Special attention was paid to low-cost and earth-abundant iron- and cobalt-based catalysts with well-defined molecular structures that could be prepared

Methods

Discussion

Conclusion