- α-Diamine Nickel Catalysts with Nonplanar Chelate Rings for Ethylene Polymerization
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A series of novel α-diamine nickel complexes, (ArNH-C(Me)-(Me)C-NHAr)NiBr2, 1: Ar=2,6-diisopropylphenyl, 2: Ar=2,6-dimethylphenyl, 3: Ar=phenyl), have been synthesized and characterized. X-ray crystallographic analysis showed that the coordination geometry of the α-diamine nickel complexes is markedly different from conventional α-diimine nickel complexes, and that the chelate ring (N-C-C-N-Ni) of the α-diamine nickel complex is significantly distorted. The α-diamine nickel catalysts also display different steric effects on ethylene polymerization in comparison to the α-diimine nickel catalyst. Increasing the steric hindrance of the α-diamine ligand by substitution of the o-methyl groups with o-isopropyl groups leads to decreased polymerization activity and molecular weight; however, catalyst thermal stability is significantly enhanced. Living polymerizations of ethylene can be successfully achieved using 1/Et2AlCl at 35 °C or 2/Et2AlCl at 0 °C. The bulky α-diamine nickel catalyst 1 with isopropyl substituents can additionally be used to control the branching topology of the obtained polyethylene at the same level of branching density by tuning the reaction temperature and ethylene pressure.
- Liao, Heng,Zhong, Liu,Xiao, Zefan,Zheng, Ting,Gao, Haiyang,Wu, Qing
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- Switching the Reactivity of Palladium Diimines with “Ancillary” Ligand to Select between Olefin Polymerization, Branching Regulation, or Olefin Isomerization
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Coordinating solvents are commonly employed as ancillary ligands to stabilize late transition metal complexes and are conventionally considered to have little effect on the reaction products. Our work identifies that the presence of ancillary ligand in Pd-diimine catalyzed polymerizations of α-olefins can drastically alter reactivity. The addition of different amounts of acetonitrile allows for switching between distinct reaction modes: isomerization–polymerization with high branching (0 equiv.), regular chain-walking polymerization (1 equiv.), and alkene isomerization with no polymerization (>20 equiv.). Optimization of the isomerization reaction mode led to a general set of conditions to switch a wide variety of diimine complexes into efficient alkene isomerization catalysts, with catalyst loading as low as 0.005 mol %.
- Jones, Glen R.,Basbug Alhan, Hatice E.,Karas, Lucas J.,Wu, Judy I.,Harth, Eva
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supporting information
p. 1635 - 1640
(2020/11/30)
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- A di-nickel complex and its preparation method and application
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The invention belongs to the field of alkene catalytic polymerization, and concretely discloses a diamine nickel complex, and a preparation method and application thereof. The complex possesses a structure shown as a formula I or II, R1 is hydrogen or alkyl, R2 is hydrogen, alkyl or phenyl, R3 is hydrogen, alkyl or phenyl, R4 is hydrogen, alkyl or phenyl, R5 is hydrogen, alkyl or phenyl, and X is a halogen. The diamine nickel complex is diverse in structure and easy to prepare. When the diamine nickel complex catalyzes ethane for active polymerization, the branching degree of the obtained polymer can be changed between medium branching degree and high branching degree by adjusting the ligand structure and changing the polymerization conditions. By using the catalyst with one specific structure, the polymer with high branching degree can be obtained at different temperatures, and the branching degree is not obviously changed along with temperature.
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Paragraph 0053-0056
(2018/05/24)
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- Synthesis, characterization of zinc complexes with neutral α-diimine ligands and application in ring-opening polymerization of σ-caprolactone
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A series of neutral α-diimine ligands with diacetyl and acenaphthenequinone skeletons were prepared by the reaction between diacetyl and the corresponding aromatic amine. These ligands reacted with ZnCl2 to generate symmetric α-diimine zinc complexes C1-C
- Wang, Xiaodan,Liu, Xuehong,Huang, Ju
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p. 773 - 776
(2017/12/08)
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- Mechanistic Insight into High-Spin Iron(I)-Catalyzed Butadiene Dimerization
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Iron complexes are commonly used in catalysis, but the identity of the active catalyst is often unknown, which prevents a detailed understanding of structure-reactivity relationships for catalyst design. Here we report the isolation and electronic structure determination of a well-defined, low-valent iron complex that is an active catalyst in the synthesis of cis,cis-1,5-cyclooctadiene (COD) from 1,3-butadiene. Spectroscopic and magnetic characterization establishes a high-spin Fe(I) center, which is supported by DFT studies, where partial metal-ligand antibonding orbital population is proposed to allow for facile ligand exchange during catalysis.
- Lee, Heejun,Campbell, Michael G.,Hernández Sánchez, Raúl,B?rgel, Jonas,Raynaud, Jean,Parker, Sarah E.,Ritter, Tobias
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supporting information
p. 2923 - 2929
(2016/11/06)
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- Nickel(II)-α-diimine complexes containing naphthyl substituents for ethylene polymerization under low ethylene pressure
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Two new α-diimine containing Ni(II) complexes, {bis[N,N′-(2,6- dimethyl-4-naphthylphenyl)imino]-1,2-dimethylethane}dibromonickel 3a and {bis[N,N′-(2-methyl-4-naphthylphenyl)imino]-1,2-dimethylethane} dibromonickel 3b were synthesized and characterized. Th
- Yuan, Jianchao,Jia, Zong,Li, Jing,Song, Fengying,Wang, Fuzhou,Yuan, Bingnian
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p. 341 - 350
(2013/06/05)
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- A thermally robust amine-imine nickel catalyst precursor for living polymerization of ethylene above room temperature
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A bulky amine-imine nickel complex containing two 2,6-diisopropyl substituents after activation with MMAO or Et2AlCl can polymerize ethylene in a living fashion over a period of 120 minutes at room temperature or above. The Royal Society of Chemistry 2012.
- Gao, Haiyang,Hu, Haibin,Zhu, Fangming,Wu, Qing
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supporting information; experimental part
p. 3312 - 3314
(2012/04/23)
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- An α-Diimine-Nickel(II) catalyst bearing an electron-withdrawing substituent for olefin polymerization
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A Br-substituted α-diimine ligand, bis[N,N′-(4-bromo-2,6- dimethylphenyl)imino]-2,3-butadiene L1, and its corresponding Ni(II) complex, {bis[N,N′-(4-bromo-2,6-dimethylphenyl)imino]-2,3-butadiene} dibromonicke [NiBr 2 (L1)], have been synthesize
- Yuan, Jianchao,Wang, Xuehu,Mei, Tongjian,Liu, Yufeng,Miao, Chengping,Xie, Xiaoli
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experimental part
p. 433 - 439
(2012/03/10)
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- Synthesis of 1,4-diazabutadienes (=N,N′-ethane-1,2- diylidenebis[amines]) by grinding
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A simple and convenient method for the synthesis of 1,4-diazabutadienes (=N,N′-ethane-1,2-diylidenebis[amines]) by grinding glyoxal (=ethanedial) or an α-diketone and anilines (=benzenamines) in the presence of TsOH in a mortar with a pestle is described.
- He, Jingyu,Xin, Hongxing,Yan, Hong,Song, Xiuqing,Zhong, Rugang
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experimental part
p. 159 - 162
(2011/03/16)
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- 1,3-Diaryl-2-imino-imidazolidines and compositions thereof
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The invention relates to new compounds of the general formula (I), STR1 wherein R1 and R5 each represent a phenyl group, optionally substituted, R2 stands for hydrogen, formyl group, carboxy group, lower alkoxycarbonyl gro
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