Issue 13, 2022

Chromium complexes supported by NNO-tridentate ligands: an unprecedented activity with the requirement of a small amount of MAO

Abstract

The development of metal catalysts with high activity and thermal stability but with the requirement of a small amount of MAO as a cocatalyst is highly desired for polyolefin industrial application. In this contribution, a series of phenoxy-imine-amine compounds were prepared and used as NNO-tridentate ligands (LH1–LH6: LH = 2,6-(R1)2–C6H3–NH–C6H4–N[double bond, length as m-dash]C-3,5–(R2)2–C6H2–OH; LH1: R1 = iPr, R2 = tBu; LH2: R1 = Me, R2 = tBu; LH3: R1 = H, R2 = tBu; LH4: R1 = F, R2 = tBu; LH5: R1 = Me, R2 = H; LH6: R1 = Me, R2 = Cl) to support chromium complexes CrCl2L(THF) (Cr1(THF)–Cr6(THF)). Upon activation with only 200 equivalents of Al(MAO), these Cr complexes exhibited extremely high activity toward ethylene polymerization and an unprecedented activity as high as 1.18 × 108 g(PE) mol−1(Cr) h−1 was obtained using Cr2(THF)/MAO. Moreover, these Cr catalysts exhibited high thermal stability, with respect to both the activity and the molecular weight. At 100 °C, Cr2(THF)/MAO showed a remarkable activity of 1.01 × 108 g(PE) mol−1(Cr) h−1 and produced polyethylene with a high molecular weight of 24.6 × 104 g mol−1. Therefore, the newly developed NNO-tridentate Cr complexes exhibiting unprecedented activity and excellent thermal stability but only requiring a small amount of MAO (as low as Al/Cr = 100) as a cocatalyst are very promising in the polyolefin industry.

Graphical abstract: Chromium complexes supported by NNO-tridentate ligands: an unprecedented activity with the requirement of a small amount of MAO

Supplementary files

Article information

Article type
Paper
Submitted
28 jan 2022
Accepted
03 mar 2022
First published
04 mar 2022

Polym. Chem., 2022,13, 1852-1860

Chromium complexes supported by NNO-tridentate ligands: an unprecedented activity with the requirement of a small amount of MAO

J. Tian, X. Zhang, S. Liu and Z. Li, Polym. Chem., 2022, 13, 1852 DOI: 10.1039/D2PY00125J

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