High molecular weight polyethylenes of narrow dispersity promoted using bis(arylimino)cyclohepta[b]pyridine-cobalt catalysts ortho-substituted with benzhydryl & cycloalkyl groups

Mingyang Han; Qiuyue Zhang; Ivan I Oleynik; Hongyi Suo; Gregory A Solan; Irina V Oleynik; Yanping Ma; Tongling Liang; Wen-Hua Sun

doi:10.1039/d0dt00576b

High molecular weight polyethylenes of narrow dispersity promoted using bis(arylimino)cyclohepta[b]pyridine-cobalt catalysts ortho-substituted with benzhydryl & cycloalkyl groups

Dalton Trans. 2020 Apr 15;49(15):4774-4784. doi: 10.1039/d0dt00576b.

Authors

Mingyang Han¹, Qiuyue Zhang¹, Ivan I Oleynik², Hongyi Suo¹, Gregory A Solan³, Irina V Oleynik², Yanping Ma⁴, Tongling Liang⁴, Wen-Hua Sun⁵

Affiliations

¹ Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. whsun@iccas.ac.cn and CAS Research/Education Center for Excellence in Molecular Sciences and International School, University of Chinese Academy of Sciences, Beijing 100049, China.
² N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Pr. Lavrentjeva 9, Novosibirsk 630090, Russia. olk@nioch.nsc.ru.
³ Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. whsun@iccas.ac.cn and Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, UK. gas8@leicester.ac.uk.
⁴ Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. whsun@iccas.ac.cn.
⁵ Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. whsun@iccas.ac.cn and CAS Research/Education Center for Excellence in Molecular Sciences and International School, University of Chinese Academy of Sciences, Beijing 100049, China and State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China.

PMID: 32211662
DOI: 10.1039/d0dt00576b

Abstract

A one-pot template strategy has been utilized to synthesize sterically enhanced bis(imino)cyclohepta[b]pyridine-cobalt(ii) chlorides, [2-{(Ar)N[double bond, length as m-dash]CMe}-9-{N(Ar)}C10H10N]CoCl2 (Ar = 2-(C5H9)-4,6-(CHPh2)2C6H2Co1, 2-(C6H11)-4,6-(CHPh2)2C6H2Co2, 2-(C8H15)-4,6-(CHPh2)2C6H2Co3, 2-(C12H23)-4,6-(CHPh2)2C6H2Co4, 2,6-(C5H9)2-4-(CHPh2)C6H2Co5). All five complexes have been characterized by a combination of FT-IR spectroscopy, elemental analysis and single crystal X-ray diffraction. The molecular structures of Co1, Co3 and Co5 highlight the substantial steric hindrance imparted by the 2-cycloalkyl-6-benzhydryl or 2,6-dicyclopentyl ortho-substitution pattern; distorted square pyramidal geometries are exhibited in each case. On activation with methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all the complexes (apart from Co4/MAO) were active ethylene polymerization catalysts (up to 3.70 × 106 g PE per mol (Co) per h for Co5/MMAO), operating effectively at temperatures between 50 °C and 60 °C, producing polyethylenes with high molecular weights (up to 589.5 kg mol-1 for Co3/MAO). Furthermore, all polymers were highly linear (Tm > 130 °C) with narrow dispersities (Mw/Mn range: 2.0-3.0). The coexistence of two chain termination pathways, β-H elimination and transfer to aluminum, has been demonstrated using 13C/1H NMR spectroscopy.