Computational study of the copolymerization mechanism of ethylene with methyl 2-acetamidoacrylate catalyzed by phosphine-sulfonate palladium complexes†
Abstract
In this research, a computational study is carried out to describe the insertion of a vital monomer, methyl 2-acetamidoacrylate (MAAA), into catalyst A (A = [(POOMe,OMe)PdMe]) (POOMe,OMe = 2[2-MeOC6H4](2-SO3-5-MeC6H4)P). Accordingly, the existence of both insertion products is found as a result of 1,2 and 2,1-insertion of MAAA in the Pd–Me bond. The 1,2-insertion of MAAA was more favorable due to the higher interaction energy among the monomers and catalyst A. Stable amide chelation was intended to hinder copolymerization and reduce the activity of catalyst A. As such, the 2,1-insertion product as a five-membered chelate could allow further insertion with a kinetically acceptable energy barrier compared to the six-membered 1,2-insertion product. The feasibility of a modified catalyst (C) (prepared from catalyst A) was also investigated to offset the effect of chelation on the copolymerization process. The newly modified catalyst (C) reduced the chelation effect by changing the steric factor around the metal (Pd) center. To upgrade the copolymer yield, the poor regioselectivity of monomer MAAA has been altered from the 1,2-insertion mode to the 2,1-insertion mode. Finally, the substituent (R) effect on C's aryl group revealed that certain substituents such as H and OMe were useful to increase the catalytic activity through the alteration of the electronic parameters.
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