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Exceptionally high molecular weight linear polyethylene by using N,N,N′‐ Co catalysts appended with a N′ ‐2,6‐bis{di(4‐fluorophenyl)methyl}‐4‐nitrophenyl group
Author(s) -
Zhang Randi,
Ma Yanping,
Han Mingyang,
Solan Gregory A.,
Pi Yaqing,
Sun Yang,
Sun WenHua
Publication year - 2019
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/aoc.5157
Subject(s) - methylaluminoxane , chemistry , aryl , steric effects , catalysis , ethylene , square pyramidal molecular geometry , yield (engineering) , medicinal chemistry , polymerization , stereochemistry , crystal structure , polymer chemistry , crystallography , metallocene , alkyl , organic chemistry , materials science , metallurgy , polymer
The bis(arylimino)pyridines, 2‐[CMeN{2,6‐{(4‐FC 6 H 4 ) 2 CH} 2 –4‐NO 2 }]‐6‐(CMeNAr)C 5 H 3 N (Ar = 2,6‐Me 2 C 6 H 3 L1 , 2,6‐Et 2 C 6 H 3 L2 , 2,6‐ i ‐Pr 2 C 6 H 3 L3 , 2,4,6‐Me 3 C 6 H 2 L4 , 2,6‐Et 2 –4‐MeC 6 H 2 L5 ), each containing one N ′‐2,6‐bis{di(4‐fluorophenyl)methyl}‐4‐nitrophenyl group, have been synthesized by two successive condensation reactions from 2,6‐diacetylpyridine. Their subsequent treatment with anhydrous cobalt (II) chloride gave the corresponding N,N,N′ ‐CoCl 2 chelates, Co1 – Co5 , in excellent yield. All five complexes have been characterized by 1 H/ 19 F NMR and IR spectroscopy as well as by elemental analysis. In addition, the molecular structures of Co1 and Co3 have been determined and help to emphasize the differences in steric properties imposed by the inequivalent N ‐aryl groups; distorted square pyramidal geometries are adopted by each complex. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), precatalyts Co1 – Co5 collectively exhibited very high activities for ethylene polymerization with 2,6‐dimethyl‐substituted Co1 the most active (up to 1.1 × 10 7 g (PE) mol −1 (Co) h −1 ); the MAO systems were generally more productive. Linear polyethylenes of exceptionally high molecular weight ( M w up to 1.3 × 10 6 g mol −1 ) were obtained in all cases with the range in dispersities exhibited using MAO as co‐catalyst noticeably narrower than with MMAO [ M w / M n : 3.55–4.77 ( Co1 – Co5 /MAO) vs . 2.85–12.85 ( Co1 – Co5 /MMAO)]. Significantly, the molecular weights of the polymers generated using this class of cobalt catalyst are higher than any literature values reported to date using related N,N,N ‐bis (arylimino)pyridine‐cobalt catalysts.