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Bis(imino)pyridines Incorporating Doubly Fused Eight-Membered Rings as Conformationally Flexible Supports for Cobalt Ethylene Polymerization Catalysts

journal contribution
posted on 2018-04-17, 13:44 authored by Z. Wang, Gregory A. Solan, Q. Mahmood, Q. Liu, Y. Ma, X. Hao, W. H. Sun
Five distinct α,α′-bis(arylimino)-2,3:5,6-bis(hexamethylene)pyridine-cobalt(II) chloride complexes, [2,3:5,6-{C 5 H 10 C(NAr)} 2 C 5 HN]CoCl 2 (Ar = 2,6-Me 2 C 6 H 3 , Co1; 2,6-Et 2 C 6 H 3 , Co2; 2,6-i-Pr 2 C 6 H 3 , Co3; 2,4,6-Me 3 C 6 H 2 , Co4; 2,6-Et 2 -4-MeC 6 H 2 , Co5), have been synthesized by one-pot template reaction of α,α′-dioxo-2,3:5,6-bis(hexamethylene)pyridine with the corresponding aniline and cobalt(II) chloride in acetic acid. The molecular structures of Co2 and Co3 reveal distorted square pyramidal geometries with two conformationally flexible eight-membered rings, a feature of the ligand manifold. On activation with either methylaluminoxane (MAO) or modified MAO (MMAO), all five complexes displayed high catalytic activities for ethylene polymerization (up to 3.62 × 10 6 g PE mol -1 (Co) h -1 ) generating strictly linear polyethylenes with the activity decreasing in the orders: Co4 > Co5 > Co1 > Co2 > Co3 (MAO) and Co1 > Co4 > Co2 > Co5 > Co3 (MMAO). Moreover, the nature of the aluminoxane cocatalyst employed had a marked effect on the molecular weight and distribution (M w /M n ) of the polymeric material obtained. For example using MAO, high molecular weight polyethylene (M w ≈ 10 5 g mol -1 ) with a narrow monomodal molecular weight distribution (2.1-3.6) was a characteristic, while using MMAO, the polyethylene was of lower molecular weight (M w ≈ 10 4 g mol -1 ) and exhibited a mono- to bimodal distribution (10.1-23.8) depending on the ratio of MMAO employed, temperature, and run time.

History

Citation

Organometallics, 2018, 37 (3), pp. 380-389

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Chemistry

Version

  • AM (Accepted Manuscript)

Published in

Organometallics

Publisher

American Chemical Society

issn

0276-7333

eissn

1520-6041

Copyright date

2018

Available date

2019-01-30

Publisher version

https://pubs.acs.org/doi/10.1021/acs.organomet.7b00809

Notes

The file associated with this record is under embargo until 12 months after publication, in accordance with the publisher's self-archiving policy. The full text may be available through the publisher links provided above.

Language

en

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