Yanning Zeng

Synthesis, characterisation and ethylene oligomerization behaviour of N -(2-substituted-5,6,7-trihydroquinolin-8-ylidene)arylaminonickel dichlorides

A series of N-(2-substituted-5,6,7-trihydroquinolin-8-ylidene)-arylaminonickel(II) dichlorides were synthesized by the one-pot stoichiometric reaction of nickel dichloride, 2-chloro- or 2-phenyl-substituted 5,6,7-trihydroquinolin-8-one, and the corresponding anilines. All nickel complexes were characterized by elemental and spectroscopic analysis. The molecular structures of representative nickel complexes, determined by the single-crystal X-ray diffraction, indicate the different coordination numbers around nickel either four with more bulky ligands or five with less bulky ligands. All nickel complexes, activated with ethylaluminium sesquichloride (Et3Al2Cl3), showed high activities (up to 9.5 × 106 g mol−1 h−1) in ethylene oligomerization for dimer and trimers.

Targeting polyethylene waxes: 9-(2-cycloalkylphenylimino)-5,6,7,8-tetrahydrocycloheptapyridylnickel halides and their use as catalysts for ethylene polymerization

A series of 9-(2-cycloalkylphenylimino)-5,6,7,8-tetrahydrocycloheptapyridine derivatives (L1–L3) was synthesized, and reacted with nickel halides to form their corresponding nickel complexes (bromide: Ni1–Ni3; chloride: Ni4–Ni6). All organic compounds and nickel complexes were well characterized. The structure of a representative complex Ni1 was determined by a single crystal X-ray study, revealing a distorted trigonal bipyramidal geometry at the nickel centre. Upon activation with either modified methylaluminoxane (MMAO) or diethylaluminium chloride (Et2AlCl), all nickel complexes showed high activities toward ethylene polymerization. The obtained polymers were confirmed to be polyethylene waxes with low molecular weights (in the range of 1.83 to 6.78 kg mol−1) and narrow polydispersity (PDI: 1.38–1.78); moreover, the obtained polyethylenes were highly branched ones. These polyethylene waxes have potential application as functional adducts of lubricants or pour-point depressants.

Ultra-high molecular weight elastomeric polyethylene using an electronically and sterically enhanced nickel catalyst

A collection of ten related 1,2-bis(imino)acenaphthene-nickel(II) halide complexes, [1-[2,6-{(C6H5)2CH}2-4-{C(CH3)3}-C6H2N]-2-(ArN)C2C10H6]NiX2 (X = Br: Ar = 2,6-Me2C6H3Ni1, 2,6-Et2C6H3Ni2, 2,6-iPr2C6H3Ni3, 2,4,6-Me3C6H2Ni4, 2,6-Et2-4-MeC6H2Ni5) and (X = Cl: Ar = 2,6-Me2C6H3Ni6, 2,6-Et2C6H3Ni7, 2,6-iPr2C6H3Ni8, 2,4,6-Me3C6H2Ni9, 2,6-Et2-4-MeC6H2Ni10), each bearing one sterically and electronically enhanced N-2,6-dibenzhydryl-4-t-butylphenyl group, have been prepared and fully characterized. The unsymmetrical nature of the chelating bis(imino)acenaphthene is confirmed in the paramagnetic 1H NMR spectra for Ni1–Ni10, while the molecular structures of Ni1, Ni2 and Ni6 highlight the unequal steric protection of the nickel center imposed by their respective N,N-ligands. On activation with either Et2AlCl or MMAO, all the nickel complexes were highly active catalysts in ethylene polymerization [as high as 1.26 × 107 g of PE per mol of Ni per h] affording exceptionally high molecular weight (up to 3.1 × 106 g mol−1) hyper-branched polyethylene. Analysis of the mechanical properties reveals the ultra-high molecular weight polymers possess high tensile strength, excellent shape fixity and elastic recovery (up to 69%) as well as high elongation at break (eb = 843.9%); such materials offer a promising alternative to current thermoplastic elastomers (TPEs).

Highly linear polyethylenes using the 2-(1-(2,4-dibenzhydrylnaphthylimino)ethyl)-6-(1-(arylimino)ethyl)-pyridylcobalt chlorides: synthesis, characterization and ethylene polymerization

The series of 2-(1-(2,4-dibenzhydrylnaphthylimino)ethyl)-6-(1-(arylimino)ethyl)pyridine derivatives and their cobalt chlorides (Co1−Co5) were synthesized and fully characterized. The representative complexes Co2 and Co3 were confirmed by single crystal X-ray diffraction analyses, indicating pseudo-square-pyramidal geometry around the cobalt centre. All cobalt complexes, activated with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), exhibited high activities towards ethylene polymerization, and produced polyethylenes with high molecular weight and highly linear feature as well as unimodal distribution.

(Co-)polymerization of methylacrylate with NBE/1-hexene by (8-arylimino-5,6,7-trihydroquinolyl)(methyl)palladium chlorides: an approaching mechanism and the polymeric microstructures

A series of methylated palladium chlorides, N-(5,6,7-trihydroquinolin-8-ylidene)arylamino PdMeCl (8-(ArN)-C9H9NPdMeCl, Ar = 2,6-Me2Ph, Pd1; 2,6-Et2Ph, Pd2; 2,6-iPr2Ph, Pd3; 2,4,6-Me3Ph, Pd4; 2,6-Et2-4-MePh, Pd5), has been prepared and fully characterized by 1H NMR, 13C NMR, FTIR spectroscopy, and elemental analysis. The solid state structures of representative complexes Pd3 and Pd4 were unambiguously confirmed by single crystal X-ray diffraction showing a slightly distorted square planar geometry around the palladium metal center. All these complexes have been found to be highly robust catalyst systems showing high catalytic activities toward the homopolymerization of methyl acrylate at elevated temperature (100 °C) and produced PMA with a molecular weight as high as 4121 kg mol−1. In addition, the Pd3 complex has good capability to incorporate norbornene (8.5%) and 1-hexene (12.7%) into the MA polymer chain. The mechanistic studies suggested that the homo(co)polymerization proceeded through a radical pathway.

Dinuclear Nickel(II) Chlorides Bearing N , N '-bis(5,6,7-trihydroquinolin-8-ylidene)-[1,1'-biphenyl]-4,4'-diamines: Synthesis and Ethylene Polymerization

Abstract5,6,7-Trihydroquinolin-8-one was condensed with the corresponding benzidine to give N,N′-bis(5,6,7-trihydroquinolin-8-ylidene)-[1,1′-biphenyl]-4,4′-diamine derivatives (L1–L3). The ligands were reacted with two equivalents of NiCl2·6H2O in a mixture of EtOH and CH2Cl2 to afford the corresponding dinickel(II) chloride complexes (Ni1−Ni3). The organic compounds were completely characterized, whilst the bi-metallic complexes were characterized by FTIR spectra and elemental analysis. These nickel complexes exhibited high activities towards ethylene polymerization in the presence of either MAO or Me2AlCl, maintaining a high activity over a prolonged period. The obtained polyethylenes were confirmed as having low molecular weights by GPC analysis.