Theoretical investigation on the model active site for isotactic polypropylene in heterogeneous Ziegler-Natta catalyst: A density functional study

The stereoselectivity of the model active site formed by the adsorption of Ti₂Cl₇ on the (1 0 0) surface of MgCl₂ was investigated by density functional calculations. The analysis of energetics for successive propylene insertions into the model active site reveals that the insertion of propylene into the model active site is energetically more favorable when a growing chain and one chlorine atom (that makes the active site chiral) are on the opposite side rather than on the same side. From this result, it is realized that the model active site is highly stereoselective. It is also observed that the Cl atoms near the growing chain significantly affect the activation energy barrier through the interaction with the growing chain.