Effect of ketimide ligand for ethylene polymerization and ethylene/norbornene copolymerization catalyzed by (cyclopentadienyl)(ketimide)titanium complexes–MAO catalyst systems: Structural analysis for Cp∗TiCl2(NCPh2)

Olefin Polymerization with Half-Metallocene Catalysts

“…1-Hexene polymerization by CpTiCl 2 (N=C t Bu 2 ) took place efficiently, and a first order relationship between the monomer concentration and the reaction rate was observed, strongly suggesting that the apparent decrease is due to the decrease in the 1-hexene concentration not due to a deactivation of the catalytically-active species. The activities by Cp'TiCl 2 [N=C(R 1 )R 2 ] were strongly affected by the ketimide substituents [69,87], and the complexes containing two t Bu groups as the ketimide substituents were effective to give polymers with unimodal molecular weight distributions, in other words, to proceed with uniform catalytically-active species. …”

“…The catalyst was reported to show higher activities than the CpTi(CH 2 Ph) 2 (NP t Bu 3 ) under the same conditions (in the presence of partially hydrolyzed Al i Bu 3 , TIBAO). However, comonomer incorporations in the copolymerization of ethylene with a-olefin, styrene, norbornene were not as high as those by the aryloxo [60][61][62][63][64][65][66][90][91][92][93][94][95] or ketimide analogues [84][85][86][87]. Taking into account the facts described above, the role of anionic donor ligand should be the key for design of more effective catalyst precursors in this catalysis.…”

“…Many examples were thus known for the copolymerization of ethylene with norbornene (NBE) using ordinary metallocenes [172][173][174][175][176], linked half-titanocenes (CGC) [56,57,120], half-titanocenes [84][85][86][87], and other so-called non-metallocenes [177][178][179][180]. However, successful examples for the efficient synthesis of random, high molecular weight copolymers with high NBE contents ([50 mol%), which possess high T g ([150°C), were limited.…”

“…The Cp-kemitide analogue, CpTiCl 2 (N=C t Bu 2 ) (3a), exhibits both remarkable activity and efficient NBE incorporation for ethylene/NBE copolymerization [87]. As shown in Table 2.8, the activity increased upon increasing in initial NBE concentration, whereas the activities by other catalysts decreased upon increasing in NBE concentration.…”

“…Many researchers thus focused on designing the catalysts with ''constrained geometry type'' for the above reason (See Reviews for linked halftitanocenes [15][16][17]46]). Scheme 2.2, have been considered as promising candidates for the efficient catalysts (Reviews for cyclic olefin copolymers [9], See Reviews for nonbridged halftitanocenes [18][19][20][40][41][42], Our initial efforts in olefin polymerization and ethylene/a-olefin copolymerization, for example [60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77]81]), because these complex catalysts display unique characteristics especially for synthesis of new polymers (See Reviews for nonbridged half-titanocenes [19,20], Ethylene copolymerization with 2-methyl-1-pentene (disubstited a-olefin) [82,83], Copolymerization with aolefin containing bulky substituents [78][79][80], Copolymerization with norbornene [84][85][86][87], Copolymerization with cyclohexene, cyclopentene [88,89], Copolymerization with styrene with efficient...…”