Ethylenebis(salicylideneiminato)zirconium Dichloride:  Crystal Structure and Use as a Heterogeneous Catalyst in the Polymerization of Ethylene

• Published in: Macromolecules 1997-01, Vol.30 (2), p.171-175
• Main Authors: Repo, Timo, Klinga, Martti, Pietikäinen, Pekka, Leskelä, Markku, Uusitalo, Anne-Marja, Pakkanen, Tuula, Hakala, Kimmo, Aaltonen, Päivi, Löfgren, Barbro
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma960512r

In the solid-state structure of the Schiff base salen [salen = N,N‘-ethylenebis(salicylideneiminato)] zirconium dichloride complex Zr(salen)Cl2(THF), C20H22Cl2N2O3Zr, a quadridentate ligand, occupies four sites in the pseudopentagonal bipyramidal coordination. The coordination sphere is completed by one THF molecule, and two chloride ions are forced into the trans-position. Removal of THF, while Zr(salen)Cl2(THF) is heated in toluene, leads to a six-coordinated complex with the two chloride ligands assuming the cis-position. This property was successfully utilized in the preparation of a homogeneous Zr(salen)Cl2 catalyst precursor. Heating of Zr(salen)Cl2(THF) in toluene in the presence of SiO2 causes deposition of Zr(salen)Cl2 on to the silica support, producing a heterogeneous catalyst, which shows an acceptable activity in ethylene polymerization at 80 °C and at low ethylene pressures in the presence of the cocatalyst methylaluminoxane.