Grafting of the zirconium complexes [Zr(η5-C5H5){NC-amidine}Cl2] and [Zr(η5-C5H5)(NC-NacNac)Cl2] and the study of their behavior in ethylene polymerization

Abstract

The synthesis of the new zirconium complex [Zr(η5-C5H5){NC-amidine}Cl2] (1) has been achieved by reaction of the amidine (E)-N-(4-cyanophenyl)-N′-(2,6-diisopropylphenyl)acetimidamide with [Zr(η5-C5H5)Cl3] and the new complex has been characterized by spectroscopic methods. The reaction of one equivalent of B(C6F5)3 with compound 1 produces the adduct [Zr(η5-C5H5){(C6F5)3B-NC-amidine}]Cl2 (2). Complexes 1 and 2 have been tested as homogeneous catalysts in olefin polymerization using MAO as cocatalyst.The grafting of 1 and the previously reported complex [Zr(η5-C5H5)(NC-NacNac)Cl2] (3) on to several inorganic solid supports, namely dehydroxylated silica (SiO2(TEMP)) (S1), dehydroxylated silica modified with O(SiMe3)2 (S2) or MAO (S3), and MgCl2 (S4) has been carried out by addition of a freshly prepared solution of 1 or 3 to the corresponding inorganic solid. FT-IR studies of the new materials showed that the links between complexes 1 or 3 and S1 and S2 occur through the zirconium center, whereas with S3 and S4 the links involve the CN functional group of the ligand. These new materials have been studied as catalysts in olefin polymerization reactions in the presence of MAO. A UV–vis study was carried out in order to identify the minimum amount of MAO necessary to produce the active species. A preliminary study into the activity in olefin polymerizations was also carried out.