Experimental and Computational Approaches on the Isospecific Role of Monoester-Type Internal Electron Donor for TiCl4 /MgCl2 Ziegler-Natta Catalysts

In this work, a combination of experimental and computational approaches on the isospecific role of monoester-type internal electron donors (ED) such as phenylpropionate (PhP), ethylheptanoate (EH), methylbenzoate (MB), ethylbenzoate (EB) for TiCl 4 /ED/MgCl 2 Ziegler-Natta catalysts had been performed. The propylene polymerization results revealed that the isospecificity of catalysts increases in the following order: PhP< EH < MB< EB. The subsequent molecular modeling on the electronic properties of the donors and two kinds of cluster model catalysts: TiCl 4 /ED/MgCl 2 and TiCl 4 /ED/(MgCl 2 ) 4 based on density functional theory (DFT) method was carried out. Two kinds of ED coordination on MgCl 2 clusters through either =O or -O- within the monoester-type ED had been disclosed. A perfect correlation between the dipole moment of ED, the coordination bond length of =O... Mg, the competitive coordination from -O- with Mg ion and the isospecificity of the catalysts had been established.