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†

Mingyang Han,

^ab Qiuyue Zhang,

^ab Ivan I. Oleynik,

*^c Hongyi Suo,

^ab Gregory A. Solan,

*^ad Irina V. Oleynik,

^c Yanping Ma,

^a Tongling Liang

^a and Wen-Hua Sun

*^abe

Author affiliations

* Corresponding authors

^a Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
E-mail: whsun@iccas.ac.cn
Fax: +86-10-62618239
Tel: +86-10-62557955

^b CAS Research/Education Center for Excellence in Molecular Sciences and International School, University of Chinese Academy of Sciences, Beijing 100049, China

^c N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Pr. Lavrentjeva 9, Novosibirsk 630090, Russia
E-mail: olk@nioch.nsc.ru

^d Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, UK
E-mail: gas8@leicester.ac.uk
Tel: +44 (0) 116-2522096

^e State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China

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 (T_m > 130 °C) with narrow dispersities (M_w/M_n 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.

Dalton Transactions

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

Abstract

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

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