1. High molecular weight polyethylenes of narrow dispersity promoted using bis(arylimino)cyclohepta[b]pyridine-cobalt catalysts ortho-substituted with benzhydryl & cycloalkyl groups.
- Author
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Han, Mingyang, Zhang, Qiuyue, Oleynik, Ivan I., Suo, Hongyi, Solan, Gregory A., Oleynik, Irina V., Ma, Yanping, Liang, Tongling, and Sun, Wen-Hua
- Subjects
MOLECULAR weights ,POLYETHYLENE ,MOLECULAR structure ,POLYETHYLENE films ,STERIC hindrance ,NUCLEAR magnetic resonance spectroscopy ,CATALYSTS - Abstract
A one-pot template strategy has been utilized to synthesize sterically enhanced bis(imino)cyclohepta[b]pyridine-cobalt(II) chlorides, [2-{(Ar)N=CMe}-9-{N(Ar)}C
10 H10 N]CoCl2 (Ar = 2-(C5 H9 )-4,6-(CHPh2 )2 C6 H2 Co1, 2-(C6 H11 )-4,6-(CHPh2 )2 C6 H2 Co2, 2-(C8 H15 )-4,6-(CHPh2 )2 C6 H2 Co3, 2-(C12 H23 )-4,6-(CHPh2 )2 C6 H2 Co4, 2,6-(C5 H9 )2 -4-(CHPh2 )C6 H2 Co5). 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 using13 C/1 H NMR spectroscopy. [ABSTRACT FROM AUTHOR]- Published
- 2020
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