Palladium‐Catalyzed Ethylene/Methyl Acrylate Co‐Oligomerization: The Effect of a New Nonsymmetrical α‐Diimine with the 1,4‐Diazabutadiene Skeleton

Abstract

AbstractPdII complexes with a nonsymmetrical bis(aryl‐imino)diazabutadiene ligand (ArDAB) have been synthesized and characterized. The new ligand features one aryl ring substituted in the ortho positions with a methyl group and the other ring that bears a trifluoromethyl group on the meta positions, which leads to subtle steric and electronic differences at the two N donor atoms. This peculiar substitution makes the direct synthesis of the ligand unfeasible, and the relevant PdII complex, [Pd(CH3)Cl(ArDAB)], is obtained directly through a template reaction. The corresponding cationic complexes with either acetonitrile or DMSO were synthesized and characterized. The X‐ray crystal structure of a Pd complex with an α‐diimine and DMSO is reported. The monocationic complexes were tested as precatalysts in ethylene/methyl acrylate co‐oligomerization under mild reaction temperature and pressure conditions. A comparison of the catalytic behavior of the precatalysts with the corresponding nonsymmetrical aryl α‐diimines with an acenaphthene skeleton indicated that the active species with the new ligand is more productive and leads to the formation of ethylene oligomers and ethylene/methyl acrylate co‐oligomers.