Titanium phosphinimide complexes for ethylene polymerization catalysis: Synthetic, computational and polymerization testing investigations.
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Chemistry and Biochemistry
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The influences of the steric and electronic properties of phosphinimide ligands on the ethylene polymerization activity of cyclopentadienyl titanium phosphinimide complexes have been investigated. These efforts resulted in a new family of very high activity ethylene polymerization catalysts and have defined the principles required for future improvements in related catalyst systems. A reliable polymerization testing method that allows control of variables which affect polymerization activity has been established. For example, a series of experiments employing the Cp*TiMe2[NP(N(Et)(Ph)) 3]/B(C6F5)3 catalyst system resulted in polymerization activities ranging from 0 to 5500 g mmol-1 hr-1 atm-1, thus illustrating the sensitivity of the catalyst activity to the polymerization conditions. Density functional theory methods were used to investigate the effects of the electronic properties of the phosphinimide ligand on the first two insertions of ethylene using the model catalyst system CpTiMe2[NPR 3]/BCl3 (R = Me, NH2, H, Cl, F). The results of this study predict that electron donating groups should increase the polymerization activity, primarily by assisting displacement of the counterion prior to coordination of ethylene. Cyclopentadienyl titanium complexes containing a phosphinimide ligand with a pendant pyridyl substituent, Cp'TiCl2[NP(R) 2(2-CH2Py)] (Cp' = Cp, Cp*, R = i-Pr, t-Bu), and the donor-acceptor complexes, CpTiCl 2[NP(R)2(2-CH2Py)·B(C6F 5)3 (R = i-Pr, t-Bu), demonstrated very low to moderate polymerization activities upon activation by MAO. Polymerization testing of Cp*TiMe2[NP(t-Bu)2(2-CH 2Py)] using B(C6F5)3 as the co-catalyst resulted in an improved catalyst system. Employing electron-donating amino (-NR1R2) substituents on the phosphinimide ligand led to the new family of very high activity ethylene polymerization catalysts of general formula Cp' TiMe2[NP(NR1R2)3]. Polymerization testing revealed a qualitative relationship between the steric bulk of the phosphinimide ligand and the polymerization activity. Under the appropriate conditions, using B(C6F5)3 as a co-catalyst, polymerization activities for these pre-catalysts ranged from 2000 to 10000 g mmol-1 hr-1 atm -1. Cp*TiMe2[NP(N(n-Pr)2) 3] demonstrated a polymerization activity of 10000 g mmol-1 hr-1 atm-1 upon activation by B(C6F5)3, nearly twice as high as the very successful pre-catalysts CpTiMe2[NP(t-Bu) 3] and Cp*TiMe2[NP(t-Bu)3] under the same conditions, and thus represents a significant advance in the development of new successful Group 4 phosphinimide ethylene polymerization catalysts.Dept. of Chemistry and Biochemistry. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2004 .B433. Source: Dissertation Abstracts International, Volume: 66-07, Section: B, page: 3703. Thesis (Ph.D.)--University of Windsor (Canada), 2004.
Beddie, Chad Lee., "Titanium phosphinimide complexes for ethylene polymerization catalysis: Synthetic, computational and polymerization testing investigations." (2004). Electronic Theses and Dissertations. 4396.