LLDPE-like Polymers Accessible via Ethylene Homopolymerization Using Nitro-Appended 2-(Arylimino)pyridine-nickel Catalysts
نویسندگان
چکیده
Four examples of para-nitro substituted 2-(arylimino)pyridine-nickel(II) bromide complexes general formula, [2-{(2,6-R-4-NO2C6H2)N=CMe}C5H4N]NiBr2, but differentiable by the steric/electronic properties displayed ortho-groups [R = i-Pr (Ni1), Et (Ni2), CHPh2 (Ni3), CH(4-FPh)2 (Ni4)], have been prepared in good yield. For comparative purposes, meta-nitro complex, [2-{(2,6-i-Pr2-3-NO2-4-(4-FPh)2C6H)N=CMe}C5H4N]NiBr2 (Ni5), has also synthesized. The molecular structures mononuclear Ni3·xH2O (x 2, 3) and bromide-bridged dinuclear Ni4 Ni5 are disclosed. Upon activation with either ethylaluminum dichloride (EtAlCl2) or modified methylaluminoxane (MMAO), all precatalysts catalytic performance at operating temperatures between 30 °C 60 higher activities generally seen using EtAlCl2 [up to 4.7 × 106 g PE (mol Ni)−1 h−1]: Ni2 ~ > Ni1 Ni3. In terms resultant polyethylene (PE), Ni4/EtAlCl2 formed highest weight series (Mw up 1.4 105 mol−1) dispersities (Mw/Mn) ranging from narrow broad (Mw/Mn range: 2.2–24.4). Moreover, melting (Tm) polymers generated via fell a range, 117.8–126.0 °C, which resembles that for industrial-grade linear-low density (LLDPE). Indeed, their 13C NMR spectra revealed significant amounts uniformly distributed long-chain branches (LCBs), while internal vinylene groups constituted major type chain unsaturation [vinylene:vinyl 5.3:1 9.9:1 (MMAO)].
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ژورنال
عنوان ژورنال: Catalysts
سال: 2022
ISSN: ['2073-4344']
DOI: https://doi.org/10.3390/catal12090961