Iminopyridine‐Nickel Precatalysts for Low Molecular Weight Branched Macro‐Olefin: Dominant β‐Elimination following Isomerization

The chain‐walking mechanism, coupled with β‐elimination reactions establish nickel complexes as a unique class of catalysts in olefin polymerization, giving access to a variety of polyethylene products from only ethylene monomer. In this study, a set of 8‐(2,6‐bis(aryl)‐3,4,5‐trifluorophenyl)imino‐5,6,7‐trihydroquinoline‐nickel bromide complexes [aryl = Ph2CH for NiH, (4‐FPh)2CH for NiF, (4‐ClPh)2CH for NiCl, (4‐MePh)2CH for NiMe, (4‐tBuPh)2CH for NitBu] was designed, prepared and investigated for ethylene polymerization. Upon activation with MAO, these precatalysts exhibited high catalytic activity (as high as 3.1 × 106 g mol‐1 h‐1) and produce polyethylene with tunable chain walking (branching degree = 58‐90/1000C), chain transfer (polymer Mw = 0.7 ‐ 2.8 kg mol‐1), and chain termination reactions (vinylene/vinyl = 83.4 ‐ 93.6%). Electron donating groups at benzhydryl of aniline showed positive influence on the rate of monomer insertion and chain propagation, resulting in high catalytic activity and polymer molecular weights. Change of chain walking and chain termination rate with reaction temperature resulted in polyethylene with varied physical state from sticky wax to thick oil. Most importantly, β‐elimination is the predominant route for chain termination reaction and producing polyethylene with high ratio of internal double bond (‐CH=CH‐/CH2=CH‐ up to 93.6%). These macromers are important for post‐modification processes.