Cyclopentadienyl Titanium Imido Compounds and Their Ethylene Polymerization Capability:  Control of Molecular Weight Distributions by Imido N-Substituents

2007 ◽  
Vol 26 (1) ◽  
pp. 83-92 ◽  
Author(s):  
Christopher T. Owen ◽  
Paul D. Bolton ◽  
Andrew R. Cowley ◽  
Philip Mountford
Keyword(s):  
Molecular Weight ◽  
Ethylene Polymerization ◽  
Molecular Weight Distributions ◽  
Weight Distributions

Titanium pyridyl-phosphinimide complexes — Synthesis, structure, and ethylene polymerization catalysis

2006 ◽  
Vol 84 (5) ◽  
pp. 755-761 ◽  
Author(s):  
Chad Beddie ◽  
Pingrong Wei ◽  
Douglas W Stephan
Keyword(s):  
Molecular Weight ◽  
Key Words ◽  
Ethylene Polymerization ◽  
Olefin Polymerization ◽  
Polymerization Catalysts ◽  
Pyridyl Group ◽  
Molecular Weight Distributions ◽  
Polymerization Catalysis ◽  
Weight Distributions

A series of Ti–pyridyl-phosphinimide complexes of the form Cp′TiX2[NPR2(2-CH2Py)] (Cp′ = Cp, Cp*, R = i-Pr, t-Bu, X = Cl, Me) have been prepared and characterized. These complexes generate ethylene polymerization catalysts upon activation with MAO or B(C6F5)3. The resulting polymers exhibit broad molecular weight distributions. The role of the pyridyl group is discussed in light of stoichiometric reactions of CpTiCl2[NPR2(2-CH2Py)] with B(C6F5)3.Key words: phosphinimide complexes, pyridyl-phosphinimides, olefin polymerization.

Boryl-substituted Zirconocene Dichloride Complexes as Catalyst Precursors for Homogeneous Ethylene Polymerization

2007 ◽  
Vol 62 (3) ◽  
pp. 314-322 ◽  
Author(s):  
Alexandra Kestel-Jakob ◽  
Helmut G. Alt
Keyword(s):  
Molecular Weight ◽  
Ethylene Polymerization ◽  
Nickel Catalysts ◽  
Synthesis And Characterization ◽  
Zirconocene Dichloride ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Methyl Aluminoxane

The synthesis and characterization of 16 new boryl-substituted zirconocene dichloride complexes are reported. After activation with methyl aluminoxane (MAO) these complexes are catalysts for homogeneous ethylene polymerization. The combination of these complexes with nickel catalysts containing Lewis basic substituents produces polymers with bimodal molecular weight distributions.

Altering molecular weight distributions: Benzyl–phosphinimide titanium complexes as ethylene polymerization catalysts

2004 ◽  
Vol 82 (8) ◽  
pp. 1304-1313 ◽  
Author(s):  
Emily Hollink ◽  
Pingrong Wei ◽  
Douglas W Stephan
Keyword(s):  
Molecular Weight ◽  
Ethylene Polymerization ◽  
Active Species ◽  
Polymerization Catalysts ◽  
Subsequent Reaction ◽  
X Ray ◽  
Molecular Weight Distributions ◽  
Polymerization Catalysis ◽  
Weight Distributions ◽  
High Yields

The phosphines and corresponding phosphinimines R2BnPNSiMe3 (R = t-Bu, Cy), p-C6H4(CH2PR2)2 (R = t-Bu (1), Cy (2)), and p-C6H4(CH2PR2NSiMe3)2 (R = t-Bu (3), Cy (4)) were prepared in high yields. Subsequent reaction with Ti precursors afforded (R2BnPN)TiCp*Cl2 (Cp* = η-C5Me5; R = t-Bu (5), Cy (6)), (R2BnPN)TiCpCl2 (Cp = η-C5H5; R = t-Bu (7), Cy (8)), p-C6H4(CH2PR2NTiCp*Cl2)2 (R = t-Bu (9), Cy (10)), and p-C6H4(CH2PR2NTiCpCl2)2 (R = t-Bu (11), Cy (12)). Methylation of the above complexes gave (R2BnPN)TiCp*Me2 (R = t-Bu (13), Cy (14)), (R2BnPN)TiCpMe2 (R = t-Bu (15), Cy (16)), p-C6H4(CH2PR2NTiCp*Me2)2 (R = t-Bu (17), Cy (18)), and p-C6H4(CH2PR2NTiCpMe2)2 (R = t-Bu (19), Cy (20)). The activity of these species as catalyst precursors in ethylene polymerization catalysis was evaluated using Schlenk line and Buchi reactor techniques using activation by methylaluminoxane (MAO) or [Ph3C][B(C6F5)4]. All these catalysts showed good activities and yield polymers with relatively broad molecular weight distributions. The bimodal polymers derived from catalysts generated using MAO are proposed to result from additional active species, possibly as a result of reaction of MAO with the benzylic fragments. X-ray data are reported for 1, 4–8, 10, 12–14, 16, and 18–20.Key words: phosphinimides, polymerization, catalysis, polyethylene, titanium, polymer molecular weight distributions.

The Use of Novel F-RAFT Agents in High Temperature and High Pressure Ethene Polymerization: Can Control be Achieved?

2007 ◽  
Vol 60 (10) ◽  
pp. 788 ◽  
Author(s):  
Markus Busch ◽  
Marion Roth ◽  
Martina H. Stenzel ◽  
Thomas P. Davis ◽  
Christopher Barner-Kowollik
Keyword(s):  
Molecular Weight ◽  
High Pressure ◽  
High Temperature ◽  
Degree Of Polymerization ◽  
Molecular Weight Distributions ◽  
High Pressure High Temperature ◽  
Reversible Addition ◽  
Weight Distributions ◽  
Raft Agent ◽  
Initial Results

Simulations are employed to establish the feasibility of achieving controlled/living ethene polymerizations. Such simulations indicate that reversible addition–fragmentation chain transfer (RAFT) agents carrying a fluorine Z group may be suitable to establish control in high-pressure high-temperature ethene polymerizations. Based on these simulations, specific fluorine (F-RAFT) agents have been designed and tested. The initial results are promising and indicate that it may indeed be possible to achieve molecular weight distributions with a polydispersity being significantly lower than that observed in the conventional free radical process. In our initial trials presented here (using the F-RAFT agent isopropylfluorodithioformate), a correlation between the degree of polymerization and conversion can indeed be observed. Both the lowered polydispersity and the linear correlation between molecular weight and conversion indicate that control may in principle be possible.

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