Title

Lewis acid-base interactions in the synthesis of titanium phosphinimide cations.

Date of Award

2004

Degree Type

Thesis

Degree Name

M.Sc.

Department

Chemistry and Biochemistry

First Advisor

Stephan, Douglas W.,

Keywords

Chemistry, Inorganic.

Rights

CC BY-NC-ND 4.0

Abstract

The active species Cp(NPtBu3)TiMe(mu-MeB(C 6F5)4) and [Cp(NPtBu3)TiMe] [B(C6F5)4], generated by the reaction of Cp(NPtBu3)TiMe2 with the activators B(C 6F5)3 and [C(C6H5) 3][B(C6F5)4], are thought to be the active species in olefin polymerization processes. Both species have been stabilized by the coordination of Lewis bases, pyridines (Py, 4-EtPy, 4- tBuPy, and 4-DMAP) and tertiary phosphines (PMe3, PnBu 3, P(C6H5)3, P(p-CH 3C6H4)3). The use of such Lewis bases allowed for the isolation and characterization of ion pair complexes of the general formula [Cp(NPtBu3)TiMe·LB] [RB(C 6F5)3] (LB = Lewis base; R = Me, C6F 5). These reactions show a dependency on the steric properties of the Lewis base. The use of sterically bulky tertiary phosphines (P(o-CH 3C6H4)3, PiPr3 , PCy3 and PtBu3) demonstrated this dependency, affording unexpected phosphonium salts as products. The role of the reaction solvent (dichloromethane and chlorobenzene) is evaluated in these reactions. Dichloromethane reacts with the reagents (active titanium complexes and Lewis bases), promoting the formation of unexpected products (some of these species are characterized). However, chlorobenzene allows a better control of the reactions between the activated complex and Lewis bases. The dimerization products [{Cp(NPtBu3)TiMe} 2(mu-Cl)] [RB(C6F5)3] (R = Me, C 6F5) (2.18), [{Cp(NPtBu 3)Ti(mu-Cl)2}][RB(C6F5)3] 2 (2.21) and [{Cp(NPtBu3)TiMe} 2(mu-Me)] [RB(C6F5)3] (2.23 ) of the cationic moiety of the active complexes [Cp(NPtBu 3)TiMe]+ showed also to be dependent on the reaction conditions and solvent. Reactions of Lewis acids (B(C6F5)3 and [C(C6H5)3][B(C6F5) 4] with Lewis bases (substituted pyridines and tertiary phosphines) are also described. A similarity in reactivity between B(C 6F5)3 and the trityl carbocation is observed, as the products afforded from these reactions are analogous. Reactions of Lewis acids and Lewis bases were found to be related to the steric bulk associated with the Lewis base in conjunction with the solvent, CH2Cl 2.Dept. of Chemistry and Biochemistry. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2004 .C33. Source: Masters Abstracts International, Volume: 43-01, page: 0216. Adviser: Douglas W. Stephan. Thesis (M.Sc.)--University of Windsor (Canada), 2004.