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Molecules 2017, 22(7), 1095; doi:10.3390/molecules22071095

Kinetics, Mechanism and Theoretical Studies of Norbornene-Ethylene Alternating Copolymerization Catalyzed by Organopalladium(II) Complexes Bearing Hemilabile α-Amino–pyridine

1
Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan
2
Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 80708, Taiwan
*
Authors to whom correspondence should be addressed.
Received: 2 June 2017 / Accepted: 27 June 2017 / Published: 30 June 2017
(This article belongs to the Special Issue Organometallic Catalysis for Olefin Polymerization/Oligomerization)
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Abstract

Cationic methylpalladium complexes bearing hemilabile bidentate α-amino–pyridines can serve as effective precursors for catalytic alternating copolymerization of norbornene (N) and ethylene (E), under mild conditions. The norbornyl palladium complexes in the formula of {[RHNCH2(o-C6H4N)]Pd(C7H10Me)(NCMe)}(BF4) (R = iPr (2a), tBu (2b), Ph (2c), 2,6-Me2C6H3 (2d), 2,6-iPr2C6H3 (2e)) were synthesized via single insertion of norbornene into the corresponding methylpalladium complexes 1a1e, respectively. Both square planar methyl and norbornyl palladium complexes exhibit facile equilibria of geometrical isomerization, via sterically-controlled amino decoordination–recoordination of amino–pyridine. Kinetic studies of E-insertion, N-insertion of complexes 1 and 2, and the geometric isomerization reactions have been examined by means of VT-NMR, and found in excellent agreement with the results estimated by DFT calculations. The more facile N-insertion in the cis-isomers, and ready geometric isomerization, cooperatively lead to a new mechanism that accounts for the novel catalytic formation of alternating COC. View Full-Text
Keywords: Norbornene–ethylene alternating copolymerization; hemilabile; amino–pyridine; palladium; geometrical isomerism; kinetics; mechanism. Norbornene–ethylene alternating copolymerization; hemilabile; amino–pyridine; palladium; geometrical isomerism; kinetics; mechanism.
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MDPI and ACS Style

Yu, K.-H.; Huang, S.-L.; Liu, Y.-H.; Wang, Y.; Liu, S.-T.; Cheng, Y.-C.; Lin, Y.-F.; Chen, J.-T. Kinetics, Mechanism and Theoretical Studies of Norbornene-Ethylene Alternating Copolymerization Catalyzed by Organopalladium(II) Complexes Bearing Hemilabile α-Amino–pyridine. Molecules 2017, 22, 1095.

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