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Q. about the Cossee-Arlman mechanism in alkene polymerization

  1. Aug 3, 2009 #1
    Starting out with TiCl4 and triethylaluminum, I understand how the triethylaluminum alkylates the TiCl4 and creates a polymeric TiCl3, but then an ethene molecule coordinates with a vacant site on the alkylated TiCl3? I thought titanium's highest oxidation state was +4?
  2. jcsd
  3. Aug 4, 2009 #2


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    That's what makes it catalytic. It lets go again.

    However... think about this. What would happen to the oxidation state of Ti+4 if you added electron density to it (in the form of a double bond)? Would it go up or down?
  4. Aug 5, 2009 #3
    The oxidation state would go down right? When the ethene molecule coordinates with the alkylated TiCl3 does it occupy an empty d orbital on the titanium atom? I suppose that would create an unstable intermediate and open the door for the olefin insertion step to create another vacant site on the titanium atom. Thank you for your help.
    Last edited: Aug 5, 2009
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