1421841-88-4Relevant articles and documents
Large-scale synthesis of novel sterically hindered acenaphthene-based α-diimine ligands and their application in coordination chemistry
Guo, Lihua,Kong, Wenyu,Xu, Yanjian,Yang, Yuliang,Ma, Rui,Cong, Li,Dai, Shengyu,Liu, Zhe
, p. 58 - 67 (2018)
An efficient method to synthesize novel highly sterically hindered acenaphthene-based α-diimine ligands bearing bulky diarylmethyl moiety was achieved by two-step reactions. These reactions could be carried out on a scale of 100 g with no chromatography involved. On the basis of this method, a series of novel highly sterically hindered acenaphthene-based α-diimine Pd(II) and Ni(II) complexes, imidazolium precursors and the corresponding NHCs-metal complexes were also successfully synthesized. These novel complexes can offer great potential for metal-catalyzed polymerizations and organic reactions.
Systematic Investigations of Ligand Steric Effects on α-Diimine Nickel Catalyzed Olefin Polymerization and Copolymerization
Gong, Yanfeng,Li, Shuaikang,Gong, Qi,Zhang, Shaojie,Liu, Binyuan,Dai, Shengyu
, p. 2919 - 2926 (2019)
So far, ligand steric effects of the α-diimine nickel catalysts on the polyolefin branching densities are not systematically investigated. Generally, in contrast to the α-diimine palladium systems, the branching densities of the polyethylene obtained by the α-diimine nickel catalysts increased when the more sterically encumbering substituent was employed. In this contribution, we described the synthesis and characterization of a series of α-diimine ligands and the corresponding nickel catalysts bearing the diarylmethyl moiety and varied steric ligands. In ethylene polymerization, the catalytic activities [(2.82-15.68) × 106 g/(mol Ni·h)], polymer molecular weights [Mn: (0.37-131.51) × 104 g mol-1], branching densities [(28-81)/1000 C], and polymer melting temperatures (-4.7-122.9 °C) can be tuned over a very wide range. To our surprise, the polymer branching density first rose and then fell when we systematically increased the steric bulk of α-diimine nickel catalysts, like a downward parabola, not in line with previous conclusions. In ethylene-methyl 10-undecenoate (E-UA) copolymerization, the catalytic activities [(1.0 × 103) - (104.8 × 104) g/(mol Ni·h)], copolymer molecular weights [(1.2 × 103) - (242.4 × 103) g mol-1], branching densities [(42-70)/1000 C], and UA incorporation ratio (0.17-2.12%) can also be controlled over a very wide range. The tuning in steric ligands enables the tuning of the polymer microstructures such as molecular weight and branching density. In this way, the best polyethylene elastomer catalysts are screened out.
Asymmetric alpha-diimine nickel (II) complex with ortho-position dimethyl benzyl substitution groups for vinyl polymerization
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Paragraph 0037; 0042-0044, (2019/07/10)
The invention belongs to the technical field of olefin polymerization, and particularly discloses an asymmetric alpha-diimine nickel (II) complex with ortho-position dimethyl benzyl substitution groups for vinyl polymerization. Large-steric-hindrance dimethyl benzyl groups are introduced to the aryl ortho position of the complex, the stability of a catalyst can be improved, the chain transfer process can be delayed, and polymers with high polymerization activity and high molecular weights can be generated. The 4'-position long-distance substitution group -CH3 of the dimethyl benzyl on an aromatic ring can more effectively partially block proceeding of chain transfer on the axial position than H substitution groups, and thus the molecular weight of produced polyvinyl is increased. Besides,by changing the steric hindrance and polymerization temperature of the complex, the catalytic activity and the physical and mechanical performance of the polymers can be effectively regulated and controlled.
