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Polymers 2017, 9(2), 53; doi:10.3390/polym9020053

DFT Studies on cis-1,4-Polymerization of Dienes Catalyzed by a Cationic Rare-Earth Metal Complex Bearing an Ancillary PNP Ligand

1
State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, China
2
College of Pharmacy, Dalian Medical University, Dalian 116044, China
3
Organometallic Chemistry Laboratory and Center for Sustainable Resource Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
*
Authors to whom correspondence should be addressed.
Academic Editor: Alexander Böker
Received: 17 December 2016 / Revised: 20 January 2017 / Accepted: 22 January 2017 / Published: 7 February 2017
(This article belongs to the Special Issue Metal Complexes-Mediated Catalysis in Polymerization)
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Abstract

Dnsity functional theory (DFT) calculations have been carried out for the highly selective cis-1,4-polymerization of butadiene catalyzed by a cationic rare-earth metal complex bearing an ancillary PNP ligand. It has been found that the chain initiation and propagation of butadiene polymerization occurs via the favorable cis-1,4-insertion route. The trans-1,4 and 1,2-insertion are unfavorable both kinetically and thermodynamically. The chain growth follows the π-allyl-insertion mechanism. The analyses of energy decomposition of transition states indicate that the likelihood of rival insertion pathways is predominantly controlled by the interaction energy of butadiene with a metal center and the deformation energy of butadiene moiety. The electronic factor of the central metal has a decisive influence on the cis- vs. trans-insertion and the regioselectivity (cis-1,4- vs. cis-1,2-insertion) is mainly determined by steric hindrance. Tetrahydrofuran (THF) coordination made monomer insertion less favorable compared with THF-free case and had more noticeable impact on the trans-monomer insertion compared with the cis case. During the chain propagation, cis-insertion of monomer facilitates THF de-coordination and the THF molecule could therefore dissociate from the central metal. View Full-Text
Keywords: density functional theory (DFT) calculations; cis-1,4-polymerization of dienes; nonmetallocene complexes; rare-earth metal density functional theory (DFT) calculations; cis-1,4-polymerization of dienes; nonmetallocene complexes; rare-earth metal
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Wang, X.; Kang, X.; Zhou, G.; Qu, J.; Hou, Z.; Luo, Y. DFT Studies on cis-1,4-Polymerization of Dienes Catalyzed by a Cationic Rare-Earth Metal Complex Bearing an Ancillary PNP Ligand. Polymers 2017, 9, 53.

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