Synthesis of Ti, Zr, and Hf complexes with a new tetra-azane ligand by one-pot HCl-elimination and their properties as catalysts for production of UHMWPE

A new anilido-imine tetra-azane ligand 1,2-[2′-(2′′,6′′-iPr2C6H3NCH)C6H4NH]2C6H4 (LH2) was synthesized and characterized. One-pot direct HCl-elimination reactions of LH2 with MCl4 (M = Ti, Zr, Hf) in toluene at room temperature at first and then at 140 °C under vacuum afforded LMCl2 [M = Ti (1a), Zr (1b), Hf (1c)] in high yields (57 ∼ 75%). It is for the first time the Zr and Hf complexes are being synthesized by the one-pot direct HCl-elimination reactions of MCl4 with a weak acidic amine-containing free ligand. All new complexes were characterized by 1H and 13C NMR spectroscopy and the molecular structures of 1a, 1b and 1c were determined by single crystal X-ray diffraction analysis. The metal centers in all complexes are six-coordinated with a distorted octahedral geometry. Upon activation with MAO or AliBu3/Ph3C+B(C6F5)4−, these complexes exhibit moderate catalytic activity for ethylene polymerization. The AliBu3/Ph3C+B(C6F5)4− activated catalyst systems produce polyethylene with ultra-high molecular weight (viscosity-averaged molecular weight Mη up to 4.29 × 106 Dalton) while the MAO activated catalyst systems show relatively good thermostability.