Synthesis, Characterization, and Comparative Study on Norbornene Polymerization of CNN and PCN Pincer Palladium Complexes

Synthesis, Characterization, and Comparative Study on Norbornene Polymerization of CNN and PCN Pincer Palladium Complexes

Several CNN pincer Pd(II) complexes including chiral complexes <b>1a</b>–<b>e</b> with 2-phenyl-6-(oxazolinyl)pyridines and achiral ones <b>2a</b>–<b>c</b> with <i>N</i>-substituted-2-aminomethyl-6-phenylpyridines were prepared. In addition...

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Bibliographic Details
Main Authors: Huizhu Wang, Jin-Kui Liu, Yi-Dong Wang, Xin-Qi Hao, Mao-Ping Song, Jun-Fang Gong, Hui Jiang
Format: Article
Language:English
Published: MDPI AG 2025-03-01
Series:Molecules
Subjects:
CNN pincer
PCN pincer
palladium-catalyzed
vinyl-type polynorbornene
Online Access:https://www.mdpi.com/1420-3049/30/7/1530
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Summary:Several CNN pincer Pd(II) complexes including chiral complexes <b>1a</b>–<b>e</b> with 2-phenyl-6-(oxazolinyl)pyridines and achiral ones <b>2a</b>–<b>c</b> with <i>N</i>-substituted-2-aminomethyl-6-phenylpyridines were prepared. In addition, the preparation of the achiral PCN pincer Pd(II) complexes <b>3a</b>–<b>e</b> with aryl-based phosphinite–imine ligands and chiral <b>4a</b>–<b>c</b> with aryl-based phosphinite–imidazoline ligands was also performed. Among them, the PCN Pd(II) pincers <b>3a</b>–<b>e</b> were new complexes and were readily synthesized from commercially available materials in only two steps. The new complexes were characterized through elemental analyses, namely <sup>1</sup>H NMR, <sup>13</sup>C{<sup>1</sup>H} NMR, and <sup>31</sup>P{<sup>1</sup>H} NMR spectroscopies. Furthermore, the molecular structure of complex <b>3a</b> was determined via X-ray single-crystal diffraction analysis. In the presence of EtAlCl<sub>2</sub>, Et<sub>2</sub>AlCl, or methylaluminoxane (MAO), the CNN pincer Pd(II) complexes and PCN pincer Pd(II) complexes exhibited excellent activities and monomer conversion rates in norbornene addition polymerization. Surprisingly, the CNN pincer Pd(II) complexes exhibited a higher conversion rate (99.5%) with Et<sub>2</sub>AlCl as the cocatalyst, while the PCN pincer Pd(II) complexes showed a higher conversion rate (98.8%) with MAO.
ISSN:1420-3049

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