Judiciously balancing steric and electronic influences on 2,3‐diiminobutane‐based Pd(II) complexes in nourishing polyethylene properties |
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| Authors: | Yanning Zeng Qaiser Mahmood Tongling Liang Wen‐Hua Sun |
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| Affiliation: | 1. Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China;2. State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China;3. CAS Research/Education Center for Excellence in Molecular Sciences, University of Chinese Academy of Sciences, Beijing, China |
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| Abstract: | A new series of palladium complexes ( Pd1–Pd5 ) ligated by symmetrical 2,3‐diiminobutane derivatives, 2,3‐bis2,6‐bis{bis(4‐FC6H4)2CH}2‐4‐(alkyl)C6H2N]C4H6 (alkyl = Me L1 , Et L2 , i Pr L3 , t Bu L4 ) and 2,3‐bis2,6‐bis{bis(C6H5)2CH}2‐4‐{(CH3)3C}C6H2N]C4H6 L5 , have been prepared and well characterized, and their catalytic scope toward ethylene polymerization have been investigated. Upon activation with MAO, all palladium complexes ( Pd1–Pd5) exhibited good activities (up to 1.44 × 106 g (PE) mol?1(Pd) h?1) and produced higher molecular weight polyethylene in the range of 105 g mol?1 with precise molecular weight distribution (M w/M n = 1.37–1.77). One of the long‐standing limiting features of the Brookhart type α‐diimine Pd(II) catalysts is that they produce highly branched (ca. 100/1000 C atoms) and totally amorphous polymer. Conversely, herein Pd5 produced polymers having dramatically lower branching number (28/1000) as well as improved melting temperature up to 73.1 °C showing well‐controlled linear architecture, and very similar to polyethylene materials generated by early‐transition‐metal based catalysts. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3214–3222 |
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| Keywords: | cationic polymerization palladium polyethylene Schiff base |
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