Syntheses and Preferred Structure Elucidation of N‐heterocyclic Imine Nickel and Cobalt Catalysts for MMA Polymerization

Abstract

AbstractHere, L1 (2‐(pyridin‐2‐yl)quinoxaline) and L2 ((1‐((1H‐pyrrol‐2‐yl)ethylidene)benzene‐1,2‐diamine) ⋅ (1‐(1H‐pyrrol‐2‐yl)ethanone)) were synthesized and reacted with CoCl2 ⋅ 6H2O and NiCl2 ⋅ 6H2O to produce complexes 1–4. We found several interesting pieces of crystal structure information. Firstly, ligands L1 and L2 with completely different molecular structures were obtained by reacting the precursors containing similar N‐heterocycles with 1,2‐diaminobenzene. Secondly, in methanol and DMF solvents, 1 showed two structures, the binuclear and mononuclear cobalt complexes 1 a and 1 b. Finally, the structure of 4 showed the formation of a new 2 : 1 type ligand at eutectic L2 in the presence of a Ni2+ template. Upon treatment with AIBN, 1–4 showed moderate to high activities for MMA polymerization, producing PMMA with low to high molecular weights (2.02∼73.03×104 g⋅mol‐1) and moderate dispersity indices (PDI: 1.72∼3.32). Moreover, 1 b displayed higher catalytic activities (up to 1.138×105 g mol−1 ⋅ h−1), which was 20 times higher than that of 3 and more than 7 times higher than that of 1 a.