ETHYLENEBIS(SALICYLIDENEIMINATO)ZIRCONIUM DICHLORIDE - CRYSTAL-STRUCTURE AND USE AS A HETEROGENEOUS CATALYST IN THE POLYMERIZATION OF ETHYLENE

In the solid-state structure of the Schiff base salen [salen = N,N'-et hylenebis(salicylideneiminato)] zirconium dichloride complex Zr(salen) Cl-2(THF), C20H22Cl2N2O3Zr, a quadridentate ligand, occupies four site s in the pseudopentagonal bipyramidal coordination. The coordination s phere is completed by one THF molecule, and two chloride ions are forc ed into the trans-position. Removal of THF, while Zr(salen)Cl-2(THF) i s heated in toluene, leads to a six-coordinated complex with the two c hloride ligands assuming the cis-position. This property was successfu lly utilized in the preparation of a homogeneous Zr(salen)Cl-2 catalys t precursor. Heating of Zr(salen)Cl-2(THF) in toluene in the presence of SiO2 causes deposition of Zr(salen)Cla on to the silica support, pr oducing a heterogeneous catalyst, which shows an acceptable activity i n ethylene polymerization at 80 degrees C and at low ethylene pressure s in the presence of the cocatalyst methylaluminoxane.