For transition metal-based olefin polymerization catalysts, ligand steric and electronic effects can strongly influence important catalytic properties. However, the simultaneous tuning of both steric and electronic ef...For transition metal-based olefin polymerization catalysts, ligand steric and electronic effects can strongly influence important catalytic properties. However, the simultaneous tuning of both steric and electronic effects has not been explored in most of the previous studies. In this contribution, a strategy to tune the ligand electronic and steric effects in a concerted fashion is reported. In such a system, both dibenzhydryl groups and multiple methoxy/fluoro groups were installed in α-diimine ligands. In addition to strongly influencing ligand electronics, the methoxy/fluoro groups can interact with the dibenzhydryl groups and efficiently increase ligand sterics. In ethylene polymerization, this concurrent tuning of electronic and steric effects can lead to simultaneous enhancement of several parameters(activity, stability, polymer molecular weight, melting point, branching density) for both the nickel and palladium catalysts. The effectiveness of this strategy is highly attractive for future studies in other catalytic systems.展开更多
Ziegler and Natta won the Nobel Prize in 1963 due to their contributions in olefin polymerization catalysis.Subsequent studies into related catalysts have led to a multibillion-dollar polyolefin industry.Currently,mor...Ziegler and Natta won the Nobel Prize in 1963 due to their contributions in olefin polymerization catalysis.Subsequent studies into related catalysts have led to a multibillion-dollar polyolefin industry.Currently,more than 178 million tons of polyolefin materials are produced annually,which constitute more than half of global plastics production.Interestingly,the metal nickel was initially recognized as a“poison”for olefin polymerization.Alkyl aluminum species can oligomerize ethylene(degree of polymerization up to 100)at high temperature and pressure;while the addition of nickel salt to the system led to the exclusive formation of 1-butene.This famous“nickel effect”marks the starting point of the era of Ziegler catalysts[1].After decades of research,the situation of nickel has changed dramatically,and a large number of nickelbased catalysts have been shown with the capabilities of producing high-molecular-weight polyethylene.As an exceptional demonstration,some groups have recently developed nickel catalysts that are able to produce ultra-high molecular weight polyethylene(UHMWPE).UHMWPE,with molecular weight of above one-million,is a special class of advanced engineering plastics with superior properties and wide applications.展开更多
基金supported by the National Natural Science Foundation of China (21690071 and 21871242)the Fundamental Research Funds for the Central Universities.
文摘For transition metal-based olefin polymerization catalysts, ligand steric and electronic effects can strongly influence important catalytic properties. However, the simultaneous tuning of both steric and electronic effects has not been explored in most of the previous studies. In this contribution, a strategy to tune the ligand electronic and steric effects in a concerted fashion is reported. In such a system, both dibenzhydryl groups and multiple methoxy/fluoro groups were installed in α-diimine ligands. In addition to strongly influencing ligand electronics, the methoxy/fluoro groups can interact with the dibenzhydryl groups and efficiently increase ligand sterics. In ethylene polymerization, this concurrent tuning of electronic and steric effects can lead to simultaneous enhancement of several parameters(activity, stability, polymer molecular weight, melting point, branching density) for both the nickel and palladium catalysts. The effectiveness of this strategy is highly attractive for future studies in other catalytic systems.
基金This work was supported by the National Natural Science Foundation of China(21690071,U19B6001 and U1904212).
文摘Ziegler and Natta won the Nobel Prize in 1963 due to their contributions in olefin polymerization catalysis.Subsequent studies into related catalysts have led to a multibillion-dollar polyolefin industry.Currently,more than 178 million tons of polyolefin materials are produced annually,which constitute more than half of global plastics production.Interestingly,the metal nickel was initially recognized as a“poison”for olefin polymerization.Alkyl aluminum species can oligomerize ethylene(degree of polymerization up to 100)at high temperature and pressure;while the addition of nickel salt to the system led to the exclusive formation of 1-butene.This famous“nickel effect”marks the starting point of the era of Ziegler catalysts[1].After decades of research,the situation of nickel has changed dramatically,and a large number of nickelbased catalysts have been shown with the capabilities of producing high-molecular-weight polyethylene.As an exceptional demonstration,some groups have recently developed nickel catalysts that are able to produce ultra-high molecular weight polyethylene(UHMWPE).UHMWPE,with molecular weight of above one-million,is a special class of advanced engineering plastics with superior properties and wide applications.
