Pd‐Iminocarboxylate Complexes and Their Behavior in Ethylene Polymerization

Designing co‐catalyst‐free late transition metal complexes for ethylene polymerization is a challenging task at the interface of organometallic and polymer chemistry. Herein, a set of new, co‐catalyst‐free, single‐component catalytic systems for ethylene polymerization have been unraveled. Treatment of anthranilic acid with various aldehydes produced four iminocarboxylate ligands ( L1 – L4 ) in very good to excellent yield (75–92 %). The existence of 2‐((2‐methoxybenzylidene)amino) benzoic acid ( L1 ) has been unambiguously demonstrated using NMR spectroscopy, MS and single‐crystal X‐ray diffraction. A neutral Pd‐iminocarboxylate complex {N O}PdMe(L1)] (N O=κ²‐N,O‐ArCHNC₆H₄CO₂ with Ar=2‐MeOC₆H₄) C1 was prepared by treating stoichiometric amount of L1.Na with palladium precursor. The identity of C1 was confirmed by 1–2D NMR spectroscopy and single‐crystal X‐ray diffraction studies. Along the same lines, palladium complexes C2 – C4 were prepared from ligands L2 – L4 respectively. In‐situ high‐pressure NMR investigations revealed that these Pd complexes are amenable to ethylene insertion and undergo facile β‐H elimination to produce propylene. These palladium complexes were then evaluated in ethylene polymerization reaction and various reaction parameters were screened. When C1 – C4 were exposed to ethylene pressures of 10–50 bar, formation of low‐molecular‐weight polyethylene was observed.