Zirconium Complexes with Bulkier Amine Bis(phenolate) Ligands and Their Catalytic Properties for Ethylene (Co)polymerization

A series of new zirconium complexes bearing bulkier amine bis(phenolate) tetradentate ligands,Me2NCH2CH2N{CH2(2-O-3-R-5-tBu-C6H2)}2ZrCl2[R =CPhMe2(1); CMePh2(2); CPh3(3); Ph (4); 3,5-Me2C6H3(5); 3,5-tBu2C6H3(6); 4-tBuC6H4(7)], were synthesized andcharacterized by1H nuclear magnetic resonance (NMR),13CNMR, and elemental analyses. The molecular structures ofcomplexes1and3were determined by single-crystal X-raydiffraction analysis. The X-ray crystallography analysis reveals thatthese complexes display a slightly distorted octahedral geometry around their metal centers. Upon activation withmethylaluminoxane (MAO), dry-MAO, MAO/butylated hydroxytoluene (BHT), or AliBu3/CPh3B(C6F5)4, these zirconiumcomplexes exhibit high catalytic activity for ethylene polymerization [up to 1.07x107g PE (mol Zr)-1h-1] and ethylene/1-hexenecopolymerization [up to 2.78x107g polymer (mol Zr)-1h-1], affording (co)polymers with moderate to high molecular weightsand good comonomer incorporations. The zirconium complexes with bulkier R groups show higher catalytic activities and longerlifetimes and produce polymers with higher molecular weights, while the zirconium complexes with aryls as R groups demonstraterelatively good comonomer incorporation ability for the copolymerization reactions. These catalytic systems also show moderatecatalytic activities for the polymerization reactions of propylene, 1-hexene, and 1-decene. Upon activation with MAO, the zirconiumcomplexes also show moderate catalytic activities for the copolymerization reaction of ethylene with 3-buten-1-ol (treated with 1equiv of AliBu3), affording copolymers with the incorporation of 3-buten-1-ol up to 1.05%