1-octene polymerization catalyzed by titanium and zirconium complexes supported by [PN] or [NPN] ligands

Ligands in homogeneous complex polymerization catalysts are crucial not only for influencing polymerization activity but also for controlling the stereoselectivity of the resulting polymers. We designed ligands on the basis of the dibenzophosphole skeleton and investigated the structure and ethylene polymerization activity of titanium and zirconium complexes activated by dried modified methylaluminoxane. In this investigation, we selected 1-octene as an α-olefin monomer and polymerized it using five types of titanium and zirconium complexes. Then, we obtained information regarding the ligand structure, polymerization activity toward 1-octene, and tacticity control. The [NPN]-Zr complex, which exhibited the highest activity for ethylene polymerization, demonstrated negligible polymerization activity for 1-octene. Conversely, titanium and zirconium complexes with [PN] ligands as auxiliary ligands exhibited activity toward 1-octene, yielding isotactic-rich polyoctene. The [PN] and [NPN] Ligands with a dibenzophosphole backbone were investigated in titanium and zirconium complexes for their roles in 1-octene polymerization. The [NPN]-Zr complex showed low activity toward 1-octene. In contrast, [PN]-ligated complexes demonstrated catalytic activity for 1-octene polymerization, with the [PN]-Zr and [PN]2Zr complexes producing oligomers at 70 °C and the [PN]2Ti complex yielding isotactic-rich polyoctene ([mm] = 66%) at −20 °C. These results highlight the critical role of ligand design in tuning polymerization activity and stereoselectivity, advancing the development of α-olefin polymerization catalysts.