Metal complexes that contain redox-active pyridine-diimine (PDI) ligands catalyze numerous reactions, including ethylene polymerization, olefin hydrosilylation, and [2+2] cycloadditions. Multinuclear (PDI)M complexes based on poly-PDI ligands may exhibit metal-metal cooperativity effects that may engender interesting reactivity. Several multinuclear (PDI)MX2 (M = Co, Fe, X = Cl, Br) complexes have been synthesized and their ethylene polymerization behavior has been investigated. However, in most cases, multinuclear PDI complexes have been synthesized with the use of binucleating templates that cannot be removed to install catalytically-active metals. Here we report that by using octahydroacirdinediketone A, in which both carbonyl moieties are constrained in the s-cis conformation, bis(pyidine-dienamine) proligand B can be readily synthesized under conventional imine-condensation conditions. Reaction of B with MCl2 salts (M = Zn, Co, Fe) in butanol yields the corresponding [bis(PDI)]M2Cl4 complexes C, which adopt chair conformations in the solid state. VT NMR studies show that C (M = Zn) undergoes macrocyclic ring inversion with a barrier of ΔG≠ = 15.3 kcal/mol at room temperature. Reaction of B with Zr(NMe2)4 yields [bis(pyridine-dienamido)]Zr2(NMe2)4 complex D, which has a static structure in solution. The ethylene polymerization behavior of C (M = Co, Fe) and D will be discussed.

Template-free synthesis of multinuclear complexes that contain macrocyclic bis(pyridine-diimine) and bis(pyridine-dienamido) ligands

2019 Spring National Meeting

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