Plastomeric-like polyethylenes achievable using thermally robust N,N'-nickel catalysts appended with electron withdrawing difluorobenzhydryl and nitro groups

A new set of five unsymmetrical N,N'-diiminoacenaphthenes, 1-[2,6-{(4-FC H ) CH} -4-NO C H N]-2-(ArN)C C H (Ar = 2,6-Me C H L1, 2,6-Et C H L2, 2,6- Pr C H L3, 2,4,6-Me C H L4, 2,6-Et -4-MeC H L5), have been synthesized and used to prepare their corresponding nickel(ii) halide complexes, LNiBr (Ni1-Ni5) and LNiCl (Ni6-Ni10). The molecular structures of Ni3(OH ) and Ni4 reveal distorted square pyramidal and tetrahedral geometries, respectively, while the H NMR spectra of all the nickel(ii) (S = 1) complexes show broad paramagnetically shifted peaks. Upon activation with either methylaluminoxane (MAO) or ethylaluminum sesquichloride (Et Al Cl , EASC), Ni1-Ni10 displayed very high activities for ethylene polymerization with the optimal performance being observed using 2,6-dimethyl-containing Ni1 in combination with EASC (1.66 × 10 g PE mol (Ni) h at 50 °C) which produced high molecular weight plastomeric polyethylene (M = 3.93 × 10 g mol , T = 70.6 °C) with narrow dispersity (M /M = 2.97). Moreover, Ni1/EASC showed good thermal stability by operating effectively at an industrially relevant 80 °C with a level of activity (6.01 × 10 g of PE mol (Ni) h ) that exceeds previously disclosed N,N'-nickel catalysts under comparable reaction conditions. This improved thermal stability and activity has been ascribed to the combined effects imparted by the para-nitro and fluoride-substituted benzhydryl ortho-substituents.