Synthesis, characterization and catalytic properties for olefin polymerization of two new dimeric zirconium(IV) complexes having diamine-bis(phenolate) and chloride ligands

• The new dimeric zirconium complexes bearing diamine bis(phenolate) were synthesized.
• The formation of active species was followed by 1H NMR spectroscopy.
• The catalytic properties in 1-olefin and ethylene polymerization were studied.
• Atacticor isotactic poli(1-octene) was formed depending on the ligand structure.
• PE with high or low molecular weight was produced depending on the ligand structure.

Reaction of the zirconium tetrachloride with one equivalent of the sodium salt of the diamine bis (phenolate) ligand, L1H2 (Me2NCH2CH2N-(CH2-2-OH-3,5-tBu-C6H2)2) or L2H2 (Me2NCH2CH2N-(CH2-2-OH-3,5-tBu-C6H2)(CH2-2-OH-C6H4)) in the presence of air led to formation of [Lig1ZrCl]2(μ-O) and [Lig2ZrCl]2(μ-O), respectively. These novel oxo-bridged dinuclear zirconium complexes were characterized by elemental analysis, 1H NMR spectroscopy and by single-crystal X-ray diffraction. Their reactivities in polymerization of ethylene and 1-octene, upon activation with Al(iBu)3/Ph3CB(C6F5)4 and MAO, were examined. It was found that lack of t-Bu substituents on one phenolate ring cause a significant decrease in catalytic activity but leads to polymers with improving properties, i.e., to poly(1-olefin)s with significantly higher stereoregularity and polyethylenes with higher molecular weight. In addition, the interaction of the [Lig1ZrCl]2(μ-O) precursors with MAO and with the Me3Al activator was investigated by 1H NMR spectroscopy giving an insight into the catalyst transformations in the course of the polymerization reaction.

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