Five amine bis(phenolate)zirconium dibenzyl complexes, [ONDO]ZrBn2, were investigated in ethylene/1-hexene copolymerization. The copolymerization behavior is sensitive both to the symmetry and connectivity of the ligand framework and to the nature of the cocatalyst. The C-2-symmetric [ONDO]ZrBn2 complexes were more active and exhibited higher comonomer incorporations than the C-2-symmetric [ONDO]ZrBn2 complexes. The nature of the cocatalyst was observed to have a significant effect on the amount of hexene incorporated into the copolymers. Activation of the C-2-symmetric [ONDO]ZrBn2 complexes with MMAO yielded copolymers with 10% higher hexene incorporation than that observed upon activation with [PhNMe2H] [B(C6F5)(4)], [B(C6F5)(3)], or [Ph3C] [B(C6F5)(4)].