Mixed ligand metallocenes as catalysts for elastomeric polypropylene

A new synthesis of unbridged mixed ring zirconocenes was developed and a se ries of mixed ligand zirconocenes with substituted 2-arylindenyl and 1-meth yl-2-arylindenyl ligands have been prepared. When activated with methylalum inoxane, the mixed ligand complexes catalyze the polymerization of propylen e to give elastomeric polypropylene. The propylene polymerization behavior of the mixed ligand catalysts was compared to that of their bis(indenyl) an alogues to determine the relative contribution of each ligand to the activi ty and stereospecificity of the catalyst. The effects of 2-arylindenyl and 1-methyl-2-arylindenyl ligands on the stereospecificity of the catalysts ar e essentially additive; the stereospecificity of the mixed ring complex is intermediate to that of the bis(2-arylindene) analogues. However, the effec t of 1-methyl substitution on catalyst productivity is not additive; the pr oductivities exhibited by bis(2-arylindenyl)ZrCl2/MAO and (1-methyl-2-aryli ndenyl)(2-arylindenyl)ZrCl2/MAO derived catalysts are similar and substanti ally higher than those of the bis(1-methyl-2-phenylindenyl)ZrCl2/MAO cataly sts.