A Zirconium Complex Bearing an [NPN] Tridentate Ligand Composed of Dibenzophosphole and Pyrrolide Moieties: Synthesis, Structure, and Ethylene-Polymerization Ability

Post-metallocene catalysts constitute a remarkable class of homogeneous olefin polymerization catalysts owing to their exceptional activity and unique ability to copolymerize ethylene with α-olefins. The synthesis of Group 4 metal complexes, adorned with unprecedented ligand frameworks, has immense potential to yield polymerization performance surpassing that of conventional catalysts. In this field, soft/hard-mix-donor-type ligands have recently emerged as a focal point in the design of novel ligands for Group 4 transition metals. Thus, we herein synthesized an [NPN]-tridentate dianionic ligand containing dibenzophosphole and pyrrolides as a new type of soft/hard base mix-donor-type ligand and its zirconium complex, denoted as [NPN]Zr(NEt2)2. The [NPN] ligand and [NPN]Zr(NEt2)2 were comprehensively characterized by NMR and single-crystal X-ray crystal analysis. Ethylene homopolymerization was conducted under various conditions to determine the polymerization activity of [NPN]Zr(NEt2)2. In particular, ethylene polymerization was conducted at 0.1 MPa and 30 °C and catalyzed with [NPN]Zr(NEt2)2 with dried modified methylalumoxane as an activator, resulting in 7600 kg of (PE) mol(Zr)−1 h–1 MPa–1 activity and linear PE with a high melting point. Overall, this study expands the repertoire of Group 4 metal catalysts, while underscoring their proficiency in tailoring advanced polymeric materials.