A group of five bis(arylimino)pyridine-cobalt(Ⅱ) chloride complexes,[2-{(2,6-(Ph2CH)2-4-MeOC6H2)N=CMe}-6-(ArN=CMe)C5H3N]CoCl2 (Ar =2,6-Me2C6H3 Co1,2,6-Et2C6H3 Co2,2,6-iPr2C6H3 Co3,2,4,6-Me3C6H2 Co4,2,6-Et2-4-MeC6H2 Co5),each containing one N-4-methoxy-2,6-dibenzhydrylphenyl group and one smaller sterically/electronically variable N-aryl group,have been synthesized in good yield (＞71％) from the corresponding neutral terdentate nitrogen-donor precursor,L1-L5.All complexes have been characterized by 1H-NMR and FTIR spectroscopy with the former highlighting the paramagnetic nature of these cobaltous species and the unsymmetrical nature of the chelating ligand.The molecular structures of Co3 and Co4 emphasize the steric differences of the two inequivalent N-aryl groups and the distorted square pyramidal geometry about the metal centers.In the presence of MAO or MMAO,Co1-Co5 collectively displayed high activities for ethylene polymerization producing high molecular weight polyethylenes that,in general,exhibited narrow dispersities (Mw/Mn values:2.12-4.07).Notably,the least sterically hindered Co1 when activated with MAO was the most productive (6.92×106 gPE·mol-1(Co)·h-1) at an operating temperature of 60 ℃.Conversely,the most sterically hindered Co3/MMAO produced the highest molecular weight polyethylene (Mw=6.29/105 g·mol-1).All the polymers displayed high linearity as demonstrated by their melting temperatures (＞ 130 ℃) and their 1H-and 13C-NMR spectra.By comparison of Co1 with its para-methyl,-chloro and-nitro counterparts,the presence of the para-methoxy substituent showed the most noticeable effect of enhancing the thermal stability of the catalyst.

Yi Yan;Shi-Fang Yuan;Ming Liu;Gregory A.Solan;Yan-Ping Ma;Tong-Ling Liang;Wen-Hua Sun

Institute of Applied Chemistry,Shanxi University,Taiyuan 030006,China;Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences,Institute of Chemistry Chinese Academy of Sciences,Beijing 100190,China;Department of Chemistry,University of Leicester,University Road,Leicester LE17RH,UK;State Key Laboratory for Oxo Synthesis and Selective Oxidation,Lanzhou Institute of Chemical Physics,Chinese Academy of Sciences,Lanzhou 730000,China

高分子科学（英文版）

[1]Yi Yan;Shi-Fang Yuan;Ming Liu;Gregory A.Solan;Yan-Ping Ma;Tong-Ling Liang;Wen-Hua Sun-.Investigating the Effects of Para-methoxy Substitution in Sterically Enhanced Unsymmetrical Bis(arylimino)pyridine-cobalt Ethylene Polymerization Catalysts)[J].高分子科学（英文版）,2022(03):266-279

Sterically,Unsymmetrical,arylimino,Ph2CH,MeOC6H2,CMe,ArN,C5H3N,Me2C6H3,Et2C6H3,iPr2C6H3,Me3C6H2,Et2,MeC6H2,dibenzhydrylphenyl,terdentate,cobaltous,MMAO,polyethylenes,dispersities,gPE

Investigating,Effects,Para,methoxy,Substitution,Enhanced,Bis,pyridine,Ethylene,Polymerization,Catalysts,five,bis,chloride,complexes,CoCl2,Co1,Co2,Co3,Co4,Co5,each,containing,one,smaller,sterically,electronically,variable,have,been,synthesized,good,yield,from,corresponding,neutral,nitrogen,donor,precursor,L1,L5,All,characterized,by,1H,NMR,FTIR,spectroscopy,former,highlighting,paramagnetic,nature,these,species,unsymmetrical,chelating,ligand,molecular,structures,emphasize,differences,two,inequivalent,groups,distorted,square,pyramidal,geometry,about,metal,centers,presence,collectively,displayed,activities,polymerization,producing,weight,that,general,exhibited,narrow,Mw,Mn,values,Notably,least,hindered,when,activated,was,most,productive,operating,Conversely,produced,highest,polymers,linearity,demonstrated,their,melting,temperatures,13C,spectra,By,comparison,its,methyl,chloro,counterparts,substituent,showed,noticeable,effect,enhancing,thermal,stability,catalyst

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