Trichlorozirconium η 2-hydrazonides: Synthesis, characterization and their catalytic behavior toward ethylene polymerization

The trichlorozirconium η 2-hydrazonides (R=H, A; R=CH3, B) were synthesized through the finely controlled stoichiometrical reactions of anhydrous zirconium tetrachloride with the lithium salt of either 1-(furan-2-ylmethylene)-2-phenylhydrazonide or 1-(furan-2-ylethylidene)-2-phenyl hydrazonide in the solvent tetrahydrofuran (THF), respectively. These complexes were highly sensitive to air and moisture due to solely using less bulky ligand of hydrazonides. The molecular structures of the title complexes, determined by means of single crystal X-ray diffraction, were found to be the distorted pentagonal bipyramid geometry around zirconium atom, with three chlorides and the hydrazonato ligand acting as the η 2-coordination mode as well as two incorporated THF molecules. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), both complexes A and B exhibited catalytic activities toward ethylene polymerization, producing polyethylenes with ultra-high molecular weights.