Synthesis and applications of functionalized pyridinyl imine complexes of palladium

Abstract

The synthesis and characterization of pyridinyl α-diimine Pd(II) complexes having a functionalized hydrocarbon attached to the imino nitrogen was performed. The catalytic activity of these complexes were then evaluated in the polymerization of ethylene and in the Heck coupling reaction of methyl acrylate with iodobenzene. Unconjugated β-diimine complexes of palladium were also synthesized and their activities towards ethylene polymerization and the Heck coupling of methyl acrylate and iodobenzene also evaluated and compared to that of the α-diimine complexes. Three of the α-diimine complexes synthesized showed activity towards ethylene polymerization, these being the complexes bearing the allyl, styrene and phenol functionalities. ω-Carboxylato complexes which were also synthesized showed no activity towards ethylene polymerization. The polymer produced was found to be high density linear polyethylene with an average PDI of 2.54 with Mn values ranging between 3.42 and 6.90 x 10-5 and Mw values ranging between 6.05 and 17.6 x 10-5. The complexes bearing the allyl, styrene and phenol functionalities, as well as the ω-carboxylato complexes active in the Heck coupling reactions of methyl acrylate with iodobenzene. None of the unconjugated β-diimine complexes prepared showed any activity towards ethylene polymerization even at high Al/Pd ratios. The activity of these complexes towards the Heck arylation reaction was comparable to that of the α-diimine complexes showing similar activities.