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 (n)butyldimethylsilyl(hexamethylindenyl) zirconium trichloride, [(Ind*(SiMe2Bu)-Bu-n)Zr(mu-Cl) Cl-2](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 kg(PE)(-1) mol(Zr)(-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 kg(PE)(-1) mol(Zr)(-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.