Tetrapyrrole bizirconium complexes as active catalysts for ethylene polymerization

Ethylene polymerization was carried out by using a group of new dizirconium(IV) tetrapyrrole complexes as catalysts and MAO as co-catalyst under 1 atmosphere pressure of ethylene gas at 25 and 40 degrees C. The highest value of catalyst activity was obtained at 40 degrees C by using bizirconium complexes including one calix[4]pyrrole between two zirconium centers and two terminal chlorines, while zirconium(IV) complexes with coordinated THF, almost have not catalytic activity. The maximum catalytic activity mounted to 830kg/mol center dot bar center dot h by Zr-2(Cy-4 Pyr (4))Cl-4. The results show that the structure of the coordination sphere of zirconium(IV) has great influence on the rate of polymerization, molar masses of forming polymer, and its molecular mass distribution.