Ethylene polymerization with homogeneous Ziegler‐Natta catalysts: theoretical study on the role of ion pairs in the polymerization mechanism

The thermodynamics of the reaction of an ethylene molecule with the Cp2TiCH3Cl/Al(CH3)2Cl system (Cp = η5‐C5H5), as a model for olefin polymerization with homogeneous Ziegler‐Natta catalysts, was investigated via quantum mechanical DFT calculations. The comparison of the calculated energies for three possible titanium‐olefin coordinated intermediates, the ionic complex Cp2TiCH3(C2H4)+/Al(CH3)2Cl , the bimetallic complex Cp2TiCH3(C2H4)δ+ · Al(CH3)2Cl and the olefin‐separated ion pair Cp2TiCH /C2H4/Al(CH3)2Cl , shows that the most feasible polymerization mechanism occurs via olefin‐separated ion pair.