The effects of replacing one of the 2-phenylindenyl-type ligands in bis(2-phenylindenyl)zirconium dichloride, (2-PhInd)2ZrCl2 (7), a catalyst precursor for the production of elastomeric polypropylene (ELPP-7), with a cyclopentadienyl-type ligand have been studied. The mixed-ring compounds:  (pentamethylcyclopentadienyl)(2-phenylindenyl)zirconium dichloride, Cp*(2-PhInd)ZrCl2, (8), (pentamethylcyclopentadienyl)(1-methyl-2-phenylindenyl)zirconium dichloride, Cp*(1-Me-2-PhInd)ZrCl2 (9), and (cyclopentadienyl)(2-phenylindenyl)zirconium dichloride, Cp(2-PhInd)ZrCl2 (10), have been synthesized through the reaction of the corresponding lithium indenide with C5R5ZrCl3 (8 and 9:  R = CH3; 10:  R = H). Crystal structures have been determined for complexes 8 and 9. The behavior of the catalysts derived from complexes 8, 9, and 10 upon their activation by methylaluminoxane (MAO) for ethylene and propylene polymerization has been studied. Of all mixed-ring catalysts only 8/MAO produces elastomeric polypropylene (ELPP-8) with properties consistent with a stereoblock microstructure. The stereosequence distributions in ELPP-8 determined from 13C NMR spectra are very similar to those in elastomeric polypropylene generated with 7/MAO under comparable conditions. However, the melting points and IR indices of 8/MAO-derived samples are significantly lower than for samples of ELPP-7 with similar isotacticity which may be attributable to shorter isotactic block lengths in ELPP-8. At the same time, comparison of 8/MAO to another metallocene system capable of producing elastomeric polypropylene rac-MeHC(Me4Cp)(Ind)TiCl2/MAO, 1/MAO, described by Chien reveals significant similarities both in the catalyst symmetry and properties of generated polypropylene. The increase of isotacticity of ELPP-8 with propylene pressure similar to the trend observed for ELPP-7 favors the two-state mechanism of stereoblock formation with 8/MAO.

Unbridged 2-arylindenylmetallocene complexes such as bis(2-phenylindenyl)zirconium dichloride in the presence of methylaluminoxane (MAO) are catalyst precursors for the synthesis of elastomeric polypropylenes. These catalysts are also active for the copolymerization of ethylene and propylene. Addition of small amounts of ethylene to a polymerization system derived from the 2-arylindene metallocenes results in a large and nonlinear increase in the polymerization rate. This increase in rate cannot be explained by the faster rate of ethylene insertion but is likely the result of the activation of dormant catalyst sites by ethylene. This "ethylene effect" is much larger for bis(2-phenylindenyl)zirconium dichloride/MAO ((2PhInd) 2ZrCl2/MAO, 1/MAO) and bis[2-(3′,5′-bis(trifluoromethyl)phenyl)indenyl]zirconium dichloride/MAO ((CF3)2PhInd)2ZrCl2/MAO, 2/MAO) metallocene catalysts than for bridged racethylene-bis(indenyl)zirconium dichloride/MAO (EBIZrCl2/MAO, 3/MAO) metallocene. Copolymerization parameters for 1-3/MAO reveal that the unbridged 2-arylindene catalysts show a tendency toward random or slightly blocky incorporation of comonomers (rerp ) 1.0-1.9 g 1), whereas the ansa-metallocene 3/MAO exhibits a tendency toward alternating comonomer distribution (rerp ) 0.5 < 1).

Unbridged 2-arylindenyl metallocene complexes, such as bis(2-phenylindenyl)zirconium dichloride, in the presence of methyaluminoxane (MAO) are catalyst precursors for the synthesis of elastomeric polypropylenes. The effects of 1-methyl substitution on the polymerization behavior of these unbridged 2-arylindene complexes have been studied. The reaction of the lithium salt of 1-methyl-2-phenylindene with ZrCl4 leads to the formation of two diastereomers of bis(1-methyl-2-phenylindenyl)zirconium dichloride:  rac - and meso -(1-Me-2-PhInd)2ZrCl2. The two isomers have been separated by fractional crystallization and identified by X-ray crystallography. X-ray crystallographic analysis reveals that the dihedral angles between the planes of the phenyl and the indenyl rings have significantly increased upon 1-methyl substitution (28−34° compared to 10−12° for unsubstituted (2-PhInd)2ZrCl2), which suggests strong steric repulsion between the 1-methyl and 2-phenyl groups. In ethylene polymerization, the productivity of the catalyst derived from the meso-isomer is similar to that of the catalyst derived from (2-PhInd)2ZrCl2; higher productivity is observed for the catalyst derived from the rac-isomer. In polymerization of propylene, both substituted catalysts have a significantly lower productivity than the catalyst derived from unsubstituted (2-PhInd)2ZrCl2 and generate amorphous polypropylene with a low molecular weight and isotacticity.

A new synthesis of unbridged mixed ring zirconocenes was developed and a series of mixed ligand zirconocenes with substituted 2-arylindenyl and 1-methyl-2-arylindenyl ligands have been prepared. When activated with methylaluminoxane, the mixed ligand complexes catalyze the polymerization of propylene to give elastomeric polypropylene. The propylene polymerization behavior of the mixed ligand catalysts was compared to that of their bis(indenyl) analogues to determine the relative contribution of each ligand to the activity and stereospecificity of the catalyst. The effects of 2-arylindenyl and 1-methyl-2-arylindenyl ligands on the stereospecificity of the catalysts are essentially additive; the stereospecificity of the mixed ring complex is intermediate to that of the bis(2-arylindene) analogues. However, the effect of 1-methyl substitution on catalyst productivity is not additive; the productivities exhibited by bis(2-arylindenyl)ZrCl2/MAO and (1-methyl-2-arylindenyl)(2-arylindenyl)ZrCl2/MAO derived catalysts are similar and substantially higher than those of the bis(1-methyl-2-phenylindenyl)ZrCl2/MAO catalysts.

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