Effect of ligands in TiCl3(OAr) catalysts for ethylene polymerization: Computational and experimental studies

Abstract

Ethylene insertion into the TiC bond at the TiCl3(OAr) catalysts in ethylene polymerization was investigated with density functional theory (DFT), in order to explore the effect of different Ar- ligands, such as C6H5-, 2,6-Me2C6H3- or 2,6-iPr2C6H3-. The computational results showed the activation energy and reaction heat of the insertion of ethylene monomer into the TiC bond in the [TiClOArCH2CH3]+ active center were between those in the [TiClCpCH2CH3]+ and [TiCl2CH2CH3]+ active centers, due to that the aryloxy group could slightly change the chemical environment of the active titanium cation. Moreover, the ethylene polymerization was carried out using these TiCl3(OAr) catalysts supported by MgCl2 (TiCl3(OAr)/MgCl2), and polyethylene (PE) was obtained with higher molecular weight and relatively narrow molecular weight distribution, like the polymerization using metallocene catalysts. The experimental results were consist with the DFT computational results, indicating that the ethylene polymerization could be controlled by adjusting the Ar- ligand in the TiCl3(OAr) catalysts.