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%

Automated summary

A series of new zirconium complexes with bulkier ligands were synthesized and their catalytic performance in ethylene polymerization and copolymerization reactions was studied. The results showed that these complexes exhibited high catalytic activity and good comonomer incorporations, and displayed excellent catalytic performance under different activation conditions.