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The soluble bis(cyclopentadienyl)bis(phenyl)titanium/methylalumoxane catalyst system produces isotactic polypropylene with a novel stereoblock microstructure consistent with a chain-end stereochemical control mechanism. Chiral catalysts derived from the racemic enantiomers of ethylene-bridged indenyl derivatives are the first metallocene catalysts to form isotactic polypropylene with the conventional structure predicted by an enantiomorphic-site stereochemical control model. The meso achiral form of the ethylene-bridged titanium indenyl diastereomers and zirconocene derivatives produce polypropylene with an ideally atactic structure. Differing regiospecificities during cis addition with soluble Ti and V chain-end controlled stereospecific systems result in Ti being isotactic specific and V being syndiotactic specific.

A series of group 4 metallocenes possessing chiral ligand environments have been characterized and their structures are compared with their propylene polymerizations. Isotactic, syndiotactic, hemiisotactic, and atactic polypropylenes are produced selectively with chiral monoalkyl metallocene cations paired with perfluorotetraphenyl borate; analogous to the results obtained using methylaluminoxane as a cocatalyst. The relative catalyst stereospecificities suggest specific π‐face selectivities and nonbonded contacts. Trends with solvents, temperatures, and catalyst structures are consistent with contact ion pairing for iPr[CpFlu]Zr‐P(+) in liquid propylene. The specificities of differently structured metallocenes imply chain‐migratory monomer addition reactions.

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