These ar special type of catalysts which is used for polymerizing different monomers to linear and stereoregular polymers. This is entirely different from radical polymerization. With these catalysts it is possible to polymerize ethylene to a highly linear chain. Both isotactic and syndiotactic polypropylene can be synthesized using this method. But usage of higher alpha olefins results only in isotactic polymers. Butadiene and isoprene on polymerization yields cis-1,4, trans-1,4, isotactic-1,2, and syndiotactic-1,2 but depending on choice of catalyst and conditions. Ziegler catalysts are metal complexes formed by the interaction of alkyl of metals with halides and other derivatives of transition metals. Hundreds of combinations are possible here. Coordination complex can be formed with the organometallic part of the system supplying some of the ligands.
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