Phosphinimide complexes with pendant hemilabile donors: synthesis, structure and ethylene polymerization activity.
The phosphines tBu(2)P(CH(2))(3)ECH(2)Ph (E = O (1), S (2)) converted to the corresponding phosphinimines (Me(3)SiN)PtBu(2)(CH(2))(3)ECH(2)Ph, E = O (3), S (4)) which were used to prepared the titanium complexes Cp'TiCl(2)NPtBu(2)(CH(2))(3)ECH(2)Ph, (E = O, Cp' = Cp (5), Cp* (6); E = S, Cp' = Cp (7), Cp* (8)). These species were subsequently methylated to the corresponding dimethyl-derivatives (9)-(12). Activation of (9)-(12) with both B(C(6)F(5))(3) and [Ph(3)C][B(C(6)F(5))(4)] was studied. For example, the [CpTiMe(NPtBu(2)(CH(2))(3)OCH(2)Ph)][MeB(C(6)F(5))(3)] (13) reacted with THF to give [CpTiMe(THF)(NPtBu(2)(CH(2))(3)OCH(2)Ph)][MeB(C(6)F(5))(3)] (14). Similar reactions gave the stable ion pairs [Cp'TiMe(NPtBu(2)(CH(2))(3)XCH(2)Ph)][MeB(C(6)F(5))(3)] (X = O, Cp' = Cp*, (15); X = S Cp' = Cp, (16), Cp*(17)) and [Cp'TiMe(NPtBu(2)(CH(2))(3)XCH(2)Ph)][B(C(6)F(5))(4)] (X = O, Cp' = Cp, (18); Cp*(19); X = S, Cp' = Cp, (20), Cp* (21)). The dihalide complexes (5)-(8), activated with MAO, proved to be ethylene polymerization catalysts of moderate activities. The dialkyl titanium complexes (9)-(12) activated with B(C(6)F(5))(3) or [Ph(3)C][B(C(6)F(5))(4)], gave catalysts that exhibited substantially higher activity and high molecular weight polyethylene. Polymerization at 60 degrees C rather than 30 degrees C significantly increased activity as well. The impact of the hemilabile donor with respect to catalyst activity is discussed. Crystallographic studies of (5) and (6) are reported.
Department of Chemistry & Biochemistry, University of Windsor, Windsor, Ontario, CanadaN9B3P4. dstephan@chem.utoronto.ca.
Krishan
K
Yadav
Jenny S J
JS
McCahill
Guangcai
G
Bai
Douglas W
DW
Stephan