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Olefin Polymerization with Half-Metallocene Catalysts

“…For example, as shown in Scheme 2.3, substituents on both cyclopentadienyl and aryloxo ligands affect the activity for ethylene polymerization (Our initial efforts in olefin polymerization and ethylene/a-olefin copolymerization, for example [60,61] BuC 5 H 4 ) Cp. The similar trend was observed in the syndiospecific styrene polymerization using a series of Cp'Ti(OMe) 3 complexes [40,109,110], and the fact would be assumed as due to a stabilization of the active site by more electron-donating substituents leading for the high activity. The t Bu 2 C 5 H 3 analogue showed lower catalytic activity in 1-hexene and 1-octene polymerization due to the steric bulk on Cp' (See Our initial efforts in olefin polymerization and ethylene/a-olefin copolymerization, for example [62,64]).…”

“…It is thus clear that these observed facts are significantly unique compared to those previously demonstarated in the copolymerization using ordinary metallocenes or linked half-titanocenes (Copolymerization with norbornene [86] Syndiotactic polystyrene (SPS) is a unique polymeric material due to its high melting point (T m =270°C), high crystallinity, low density, low dielectric constant, and high chemical resistance toward organic solvents [10,40,109,110, Example concerning syndiospecific styrene polymerization by half-titanocene complexborate catalyst [185][186][187]). This polymer cannot be prepared by free radical, anionic or ordinary Ziegler-Natta processes, but can be prepared by the syndiospecific polymerization using various half-titanocenes (Scheme 2.10), Cp'TiX 3 or Cp'TiX 2 (Y) (Cp' = cyclopentadienyl group; X = halogen, alkoxo, alkyl etc.…”

“…On the basis of structural data in Cp'TiCl 2 (O-2,6-i Pr 2 C 6 H 3 ), the bond angle (173.0°) of Ti-O-C (phenoxy) for Cp*TiCl 2 (O-2,6-i Pr 2 C 6 H 3 ) (2a), which was the most effective catalyst precursor, is significantly different from those for the other Cp derivatives, (Cp'=Cp, 1,3-t Bu 2 C 5 H 3 , 163.0-163.1°): the large Ti-O-C bond angle would lead to more O ? Ti p donation into Ti (Our initial efforts in olefin polymerization and ethylene/a-olefin copolymerization, for example [60,61] [109,110]. The aryloxo substituent in the ortho position not only affects the stabilization, but also affects the R-Tiethylene bond angle that should be important for the subsequent insertion.…”

“…Ordinary half-titanocenes such as Cp*TiCl 3 , Cp*Ti(OMe) 3 , (indenyl)TiCl 3 are known to be efficient catalyst precursors for syndiospecific styrene polymerization in the presence of a co-catalyst [10,40,109,110,218,[221][222][223][224][225][226] (Fig 2.2). Example concerning syndiospecific styrene polymerization by half-titanocene complex-borate catalyst [185][186][187], Examples of a mechanistic studies for styrene polymerization [227][228][229]).…”

“…), which are efficient catalyst precursors for syndiospecific styrene polymerization ( [10,40,109,110,218,[221][222][223][224][225][226], Example concerning syndiospecific styrene polymerization by half-titanocene complex-borate catalyst [185][186][187]), afforded a mixture of polyethylene (PE), syndiotactic polystyrene (SPS) and the copolymer (E/S copolymer) in the ethylene/styrene (co)polymerization (Copolymerization with styrene with efficient styrene incorporation or in a living manner [93], The product distribution and the [194][195][196][197][198]). The product distribution and the activity in (co)polymerization using a CpTiX 3 -MAO catalyst system is thus highly sensitive to the anionic donor ligand (X=Cl, CH 2 Ph, OCH 3 , OCH 2 Ph etc.…”