220246-25-3Relevant articles and documents
Mixed ligand metallocenes as catalysts for elastomeric polypropylene
Tagge, Christopher D.,Kravchenko, Raisa L.,Lal, Tappan K.,Waymouth, Robert M.
, p. 380 - 388 (2008/10/08)
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.
