Qifeng Xing

Synthesis, characterization and ethylene polymerization behavior of binuclear iron complexes bearing N,N′-bis(1-(6-(1-(arylimino)ethyl) pyridin-2-yl)ethylidene)benzidines

A series of N,N′-bis(1-(6-(1-(arylimino)ethyl)pyridin-2-yl)ethylidene)benzidines and the bi-metallic iron complexes thereof have been synthesized and fully characterized. All iron complexes, when activated by MAO or MMAO, exhibited high activities of up to 1.3 × 107 g mol−1 (Fe) h−1 for the polymerization of ethylene. On comparison with their mononuclear counterparts, such bi-metallic complexes not only retain a relatively high activity at elevated temperatures (up to 70 °C), but also exhibit increased lifetimes. The polyethylenes obtained were characterized by GPC, DSC and high temperature NMR spectroscopy, which indicated multimodal and highly linear features.

Enhancing catalytic activity towards Heck-reaction by using 4,5,9,10-tetra(arylimino)pyrenylidenyldipalladium tetrachlorides

A series of binuclear 4,5,9,10-tetra(arylimino)pyrenylidenyldipalladium(II) tetrachloride complexes (Pd1–Pd4) was synthesized and characterized by FT-IR and NMR spectroscopy as well as elemental analysis. The molecular structures of representative complexes Pd1 and Pd2 were determined by single crystal X-ray diffraction to reveal a square planar geometry around the palladium centre. The complex Pd1 dissolved in the presence of ethanol to form mono-palladium complex C1, whose structure was also confirmed by single crystal X-ray diffraction. All binuclear palladium complexes promote the Heck cross-coupling reactions with high activities; the reaction can be carried out for various substrates and activators (basic compounds) and also in various solvents. The binuclear palladium complexes exhibit significantly higher efficiency than do their mono-palladium complexes bearing 4,5-bis(arylimino)pyrenylidenes.

Frustratingly synergic effect of cobalt–nickel heterometallic precatalysts on ethylene reactivity: the cobalt and its heteronickel complexes bearing 2-methyl-2,4-bis(6-aryliminopyridin-2-yl)-1H-1,5-benzodiazepines

A series of 2-methyl-2,4-bis(6-aryliminopyridin-2-yl)-1H-1,5-benzodiazepines were reacted with cobalt chloride to form their corresponding cobalt complexes, which were further reacted with nickel chloride to form their binuclear heteronickel complexes. One of the representative cobalt–nickel complexes was unambiguously confirmed using single-crystal X-ray diffraction. Generally all mononuclear cobalt complexes and binuclear cobalt–nickel complexes showed good activities towards ethylene reactivity (oligomerization and polymerization), however, the mononuclear cobalt complexes showed much higher activities than the binuclear cobalt–nickel analogues, and this is described as the frustratingly synergic effect of heterometallic complexes in ethylene oligomerization. In addition, the obtained oligomers sometimes followed a Poisson distribution.

Trichlorozirconium η 2-hydrazonides: Synthesis, characterization and their catalytic behavior toward ethylene polymerization

The trichlorozirconium η2-hydrazonides (R=H, A; R=CH3, B) were synthesized through the finely controlled stoichiometrical reactions of anhydrous zirconium tetrachloride with the lithium salt of either 1-(furan-2-ylmethylene)-2-phenylhydrazonide or 1-(furan-2-ylethylidene)-2-phenyl hydrazonide in the solvent tetrahydrofuran (THF), respectively. These complexes were highly sensitive to air and moisture due to solely using less bulky ligand of hydrazonides. The molecular structures of the title complexes, determined by means of single crystal X-ray diffraction, were found to be the distorted pentagonal bipyramid geometry around zirconium atom, with three chlorides and the hydrazonato ligand acting as the η2-coordination mode as well as two incorporated THF molecules. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), both complexes A and B exhibited catalytic activities toward ethylene polymerization, producing polyethylenes with ultra-high molecular weights.

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.