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The sterically and electronically modified cycloheptyl‐fused bis(arylimino)pyridine‐cobalt(II) chloride precatalysts [2,3 : 5,6‐{C4H8C(N‐2,4‐(C15H13)‐6‐R‐C6H2}2C5HN]CoCl2 (R=Me (Co1), Et (Co2), i‐Pr (Co3), Cl (Co4), and F (Co5)) have been prepared via one‐pot synthesis approach. All the precatalysts were characterized by elemental analysis, FT‐IR spectroscopy and the single‐crystal X‐ray diffraction for Co2 confirmed distorted‐square‐pyramidal geometry around the cobalt center. On activation with either MAO (methylaluminoxane) or MMAO (modified methylaluminoxane), all the cobalt precatalysts displayed high catalytic activities for ethylene polymerization with peak performance of 3.47×106 g (PE) mol−1 (Co) h−1 at 50 °C using MAO and 4.53×106 g (PE) mol−1 (Co) h−1 at 30 °C with MMAO. The steric and electronic influence of the ortho‐substitutions (R) displayed significant effect on the catalytic activity and molecular weight of the resultant polyethylene. Notably, the precatalyst Co5 (R=F) exhibited high activity, delivering high‐molecular‐weight (558.17 kg mol−1) polyethylene; highlights the beneficial effect of ortho‐substituents (R) alongside with dibenzocycloheptyl groups. In addition, analysis of the obtained polyethylene showed strictly linear structure with saturated and unsaturated (vinyl) end groups. [ABSTRACT FROM AUTHOR]

Five examples of unsymmetrical 1,2‐bis (arylimino) acenaphthene (L1 – L5), each containing one N‐2,4‐bis (dibenzocycloheptyl)‐6‐methylphenyl group and one sterically and electronically variable N‐aryl group, have been used to prepare the N,N′‐nickel (II) halide complexes, [1‐[2,4‐{(C15H13}2–6‐MeC6H2N]‐2‐(ArN)C2C10H6]NiX2 (X = Br: Ar = 2,6‐Me2C6H3Ni1, 2,6‐Et2C6H3Ni2, 2,6‐i‐Pr2C6H3Ni3, 2,4,6‐Me3C6H2Ni4, 2,6‐Et2–4‐MeC6H2Ni5) and (X = Cl: Ar = 2,6‐Me2C6H3Ni6, 2,6‐Et2C6H3Ni7, 2,6‐i‐Pr2C6H3Ni8, 2,4,6‐Me3C6H2Ni9, 2,6‐Et2–4‐MeC6H2Ni10), in high yield. The molecular structures Ni3 and Ni7 highlight the extensive steric protection imparted by the ortho‐dibenzocycloheptyl group and the distorted tetrahedral geometry conferred to the nickel center. On activation with either Et2AlCl or MAO, Ni1 – Ni10 exhibited very high activities for ethylene polymerization with the least bulky Ni1 the most active (up to 1.06 × 107 g PE mol−1(Ni) h−1 with MAO). Notably, these sterically bulky catalysts have a propensity towards generating very high molecular weight polyethylene with moderate levels of branching and narrow dispersities with the most hindered Ni3 and Ni8 affording ultra‐high molecular weight material (up to 1.5 × 106 g mol−1). Indeed, both the activity and molecular weights of the resulting polyethylene are among the highest to be reported for this class of unsymmetrical 1,2‐bis (imino)acenaphthene‐nickel catalyst. [ABSTRACT FROM AUTHOR]