A counterintuitive, yet efficient synthesis of bis(indenyl)zirconium dihalides

Abstract

The use of bisindenyl zirconium dimethyl in the synthesis of the corresponding dihalides is described. The synthesis of Ind 2ZrCl 2 has been carried out, cleanly and quantitatively, by chlorination of Ind 2ZrMe 2 ( 2) with a variety of inorganic chlorides, including BCl 3, SCl 2 in either toluene or methylene chloride, and HCl in Et 2O. The latter method is the preferred one, since it produces methane as the only byproduct, and the formed Ind 2ZrCl 2 precipitates quantitatively from the Et 2O solvent: a simple filtration then gives the analytically pure product in quantitative yield. Ind 2ZrBr 2 and Ind 2ZrI 2 are obtained by reacting 2 with Br 2 and I 2, respectively. The ‘inverse’ synthesis of metallocene dichlorides by chlorination of their dimethyl ‘derivatives’ has advantages compared to the classic method: first, Ind 2ZrCl 2 is obtained in higher yield (90–96%); second, it is easier to purify (at the dimethyl stage) and is obtained free from LiCl. Five bisindenyl zirconium complexes with different sigma ligands have been investigated in solution propylene polymerizations: it is found that the σ-ligands have no relevant influence on the catalyst activity, nor on the polymer properties.