Synthesis and characterisation of permethylindenyl zirconium complexes and their use in ethylene polymerisation†
We report the synthesis of two zirconocenes, dimethylsilylbis(hexamethylindenyl) zirconium dichloride, rac-(SBI*)ZrCl2, and nbutyldimethylsilyl(hexamethylindenyl) zirconium trichloride, [(Ind*SiMe2nBu)Zr(μ-Cl)Cl2]2. The complexes were characterised by NMR spectroscopy and X-ray crystallography, and the bonding was evaluated using density functional theory. rac-(SBI*)ZrCl2 demonstrated a very high activity for solution phase polymerisation of ethylene (ca. 22 500 kgPE−1 molZr−1 h−1 bar−1). Both rac-(SBI*)ZrCl2 and rac-(EBI*)ZrCl2 (EBI* = ethylenebis(hexamethylindenyl)) have been supported on MAO modified silica and AMOST layered double hydroxides (AMO-LDHs), and evaluated as catalysts in the slurry-phase polymerisation of ethylene. The highest catalytic polymerisation activities for rac-(SBI*)ZrCl2 and rac-(EBI*)ZrCl2 on the layered double hydroxides were 9657 and 4325 kgPE−1 molZr−1 h−1 bar−1 respectively, for MAO modified Mg2Al–SO4 LDH. However, rac-(EBI*)ZrCl2 was a three times more active catalyst than rac-(SBI*)ZrCl2 when supported on silica.