Chromium ethylene polymerization catalysts bearing sterically enhanced α, α′-bis(imino)-2,3:5,6-bis(pentamethylene)pyridines: Tuning activity and molecular weight

POLYMER

卷:171

Article

Bariashir, Chantsalnyam^1,2,3  Wang, Zheng^1,2,3  Solan, Gregory A.^1,2,4  Huang, Chuanbing^1,2,3  Hao, Xiang^1,2  Sun, Wen-Hua^1,2,3,5 

[1] Chinese Acad Sci, Inst Chem, Key Lab Engn Plast, Beijing 100190, Peoples R China

[2] Chinese Acad Sci, Inst Chem, Beijiag Natl Lab Mol Sci, Beijing 100190, Peoples R China

[3] Univ Chinese Acad Sci, CAS Res Educ Ctr Excellence Mol Sci, Beijing 100049, Peoples R China

[4] Univ Leicester, Dept Chem, Univ Rd, Leicester LE1 7RH, Leics, England

[5] Chinese Acad Sci, Lanzhou Inst Chem Phys, State Key Lab Oxo Synth & Select Oxidat, Lanzhou 730000, Gansu, Peoples R China

关键词: Ethylene polymerization;    Chromium precatalysts;    alpha-alpha '-bis(arylimino)-2,3:5,6-bis(pentamethylene)pyridine;    Electronic and steric effects;   

DOI  :  10.1016/j.polymer.2019.03.038

来源: Elsevier

【 摘 要 】

The ortho-benzhydryl-substituted alpha, alpha'-bis(arylimino)-2,3:5,6-bis(pentamethylene) pyridine-chromium(III) chlorides, [2,3:5,6-{C4H8C(N(2-R-1-4-R-2-6-(CHPh2)C6H2)}(2)C5HN] CrCl3 [R-1 = R-2 = Me Cr1, R-1 = Me, R-2 = CHPh2 Cr2, R-1 = Et, R-2 = CHPh2 Cr3, R-1 = i-Pr, R-2 = CHPh2 Cr4, R-1 = Cl, R-2 = CHPh2 Cr-5, R-1 = F, R-2 = CHPh2 Cr6], differing in the electronic and/or steric properties of their aryl-R-1 and -R-2 groups, have been prepared by a one-pot template approach involving a, a'-dioxo-2,3: 5,6-bis(pentamethylene) pyridine, the corresponding aniline and CrCl3(THF) 3 in acetic acid. The molecular structure of six-coordinate Cr1 reveals the carbocyclic-fused N, N, N-ligand to adopt a mer configuration with the puckered sections of the two fused rings arranged mutually cis. On activation with MAO or MMAO, Cr1 -Cr6 displayed high activities (up to 1.83 x 10(6) g (PE) mol(-1) (Cr) h(-1)) for the polymerization of ethylene with the MAO-promoted polymerizations in most cases more productive than with MMAO. In general, the chromium complexes appended with ortho-halide substituents (Cr6 (F)) and (Cr5 (C1)), proved the most active with the overall order being: Cr6 > Cr5 > Cr1 > Cr2 > Cr3 > Cr4. All catalysts formed linear polyethylene displaying a wide range of molecular weights (from 2.17 to 300.4 kg mol-1) that were highly dependent on the nature of the ortho-R-1 substituent with fluoride Cr6 forming the lowest molecular weight and the most sterically demanding Cr4 (i-Pr) the highest.

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