Thermally Stable and Highly Efficient N,N,N-Cobalt Olefin Polymerization Catalysts Affixed with N-2,4-Bis(Dibenzosuberyl)-6-Fluorophenyl Groups

The cobalt(II) chloride N,N,N-pincer complexes, [2-{(2,4-(C15H13)2-6-FC6H2)N=CMe}-6-(ArN=CMe)C5H3N]CoCl2 (Ar = 2,6-Me2C6H3) (Co1), 2,6-Et2C6H3 (Co2), 2,6-i-Pr2C6H3 (Co3), 2,4,6-Me3C6H2 (Co4), 2,6-Et2-4-MeC6H2 (Co5), and [2,6-{(2,4-(C15H13)2-6-FC6H2)N=CMe}2C5H3N]CoCl2 (Co6), each containing at least one N-2,4-bis(dibenzosuberyl)-6-fluorophenyl group, were synthesized in good yield from their corresponding unsymmetrical (L1–L5) symmetrical bis(imino)pyridines (L6). molecular structures of Co1 Co2 spotlighted distorted square pyramidal geometries (τ5 value range: 0.23–0.29) variations steric hindrance offered by the dissimilar N-aryl groups. On activation with either MAO or MMAO, Co1–Co6 all displayed high activities for ethylene polymerization, levels falling order: > Co4 Co5 Co3 Co6. Indeed, sterically hindered 2,6-dimethyl combination exhibited a very activity 1.15 × 107 g PE mol−1 (Co) h−1 operating temperature 70 °C, which dropped only 15% 80 °C 43% 90 °C. Vinyl-terminated polyethylenes linearity narrow dispersity generated catalysts, most hindered, Co6, producing highest weight polymers [Mw 30.26–33.90 kg (Co3) 42.90–43.92 (Co6)]. In comparison structurally related cobalt it was evident that presence groups had limited effect on catalytic but marked thermal stability.