Synthesis of liquid oligopropylene oil by binuclear iminopyridyl nickel catalysts

• Hyperbranched polypropylene-based oligomer oils with tunable molecular wights and branching degrees are prepared. • Enhanced catalytic activities and thermal stability were achieved due to cooperative effect of the binuclear structure. • The binuclear catalyst also showed good compatibility with other α -olefins to access oligomer oils. Propylene oligomers obtained via late-transition-metal (Ni, Pd) catalysis are regarded as attractive and cost-effective alternatives to conventional PAOs; however, their practical application is often limited by the relatively low catalytic activity of such systems. In this study, two phenylene-bridged binuclear iminopyridyl nickel complexes, meta- Ni1 and para- Ni1 , were synthesized and evaluated for propylene oligomerization. Compared with the mononuclear analogue, complex para - Ni1 exhibited relative higher catalytic activity and improved thermal stability, offering an effective strategy to enhance the performance of Ni-based catalytic systems. DFT calculations revealed that the enhanced activity originates primarily from the Ni···Ni cooperative effect, which lowers the energy barrier for monomer insertion. Furthermore, by systematically varying the reaction conditions, viscous liquid oligopropylenes with tunable molecular weights (0.32–0.99 × 10 3 g·mol -1 ) and branched microstructures were facilely obtained. These results demonstrate that the binuclear iminopyridyl nickel framework provides an effective platform for the synthesis of hyperbranched polypropylene-based lubricant oils from abundant and low-cost propylene feedstock.