| 초록 |
The stereoselective propylene insertion in MgCl2-supported Ziegler-Natta catalysts was investigated by density functional calculations. For this purpose, the energetics of propylene insertion on the model active site formed by the adsorption of Ti2Cl7 on the (100) surface of MgCl2 was calculated. From the energy profiles, it is proposed that this active site is highly stereoselective. In particular, in contrast to previous molecular mechanics studies, propylene insertion is energetically more favorable when growing chain and the chlorine atom (that makes active site chiral) are on the same side rather than on the opposite side, which discriminates between two prochiral faces of propylene monomer. The electron densities of the chlorine atoms near the growing chain significantly affect the activation barriers, and the interactions between the growing chain and the chlorine atoms cooperatively stabilize the transition state, which results in low activation barrier. |
