Metallocene catalysts bridging groups

For example, it is possible to synthesize isotactic as well as syndiotactic polypropylene in high configurational purity and high yields. The same holds for syndiotactic polystyrene. Furthermore, metallocene catalysts open the possibility to absolutely new homopolymers and copolymers like, e.g., cycloolefin copolymers (COG) and even (co)polymers of polar monomers.The simplest metallocene catalyst consists of two components. The first one is a n-complex (the actual metallocene) that can be bridged via a group X and therefore can become chiral ... 

Patents have been reported for a series of bimetallic metallocene catalysts based on lanthanide and group IV metals. The bridging ligand is a substituted ethyl-linked fluorenyl indenyl bearing a substituent of varying length [26]. The complexes are reported to act as good olefin polymerization catalysts in the presence of MAO.52,53... 

The extent to which the metallocene Iramework can be modified is extraordinary indeed, with from one to four different substituents on each ring or a covalent bridging group like 1,2-ethylene or dimethylsUyl to lock the rings into one particular conformation and open the active site to varying degree. All these factors have an influence on catalyst performance and polymers produced. An example... 

Ansa-metallocenes tethered to a silica surface through the bridging group have been prepared by reacting ClMeSi(Cp)2MCl2 (M = Zr, HI) with partially dehydroxylated silica, either by itself or modified by agents such as (MeO)3Si(CH2)3NH2. The catalyst activity in ethylene-1-hexene copolymerization is... 

COC) and even (co)polymers of polar monomers. The simplest metallocene catalyst consists of two components. The first one is a 7i-complex (the actual metallocene) that can be bridged via a group X and therefore can become chiral ... 

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