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, Me 2 NCH 2 CH 2 N{CH 2 (2-O-3-R-5- t Bu-C 6 H 2 )} 2 ZrCl 2 [R = CPhMe 2 ( 1 ); CMePh 2 ( 2 ); CPh 3 ( 3 ); Ph ( 4 ); 3,5-Me 2 C 6 H 3 ( 5 ); 3,5- t Bu 2 C 6 H 3 ( 6 ); 4- t BuC 6 H 4 ( 7 )], were synthesized and characterized by 1 H nuclear magnetic resonance (NMR), 13 C NMR, and elemental analyses. The molecular structures of complexes 1 and 3 were determined by single-crystal X-ray diffraction analysis. The X-ray crystallography analysis reveals that these complexes display a slightly distorted octahedral geometry around their metal centers. Upon activation with methylaluminoxane (MAO), dry-MAO, MAO/butylated hydroxytoluene (BHT), or Al i Bu 3 /CPh 3 B(C 6 F 5 ) 4 , these zirconium complexes exhibit high catalytic activity for ethylene polymerization [up to 1.07 × 10 7 g PE (mol Zr) -1 h -1 ] and ethylene/1-hexene copolymerization [up to 2.78 × 10 7 g polymer (mol Zr) -1 h -1 ], affording (co)polymers with moderate to high molecular weights and good comonomer incorporations. The zirconium complexes with bulkier R groups show higher catalytic activities and longer lifetimes and produce polymers with higher molecular weights, while the zirconium complexes with aryls as R groups demonstrate relatively good comonomer incorporation ability for the copolymerization reactions. These catalytic systems also show moderate catalytic activities for the polymerization reactions of propylene, 1-hexene, and 1-decene. Upon activation with MAO, the zirconium complexes also show moderate catalytic activities for the copolymerization reaction of ethylene with 3-buten-1-ol (treated with 1 equiv of Al i Bu 3 ), affording copolymers with the incorporation of 3-buten-1-ol up to 1.05%.