Influence of chelate ring size on the properties of phosphine-sulfonate palladium catalysts

Abstract

Phosphine-sulfonate based palladium is one of the most extensively studied catalyst systems in olefin polymerization. This type of catalyst features six-membered chelate ring size, and can enable the copolymerizations of ethylene with a wide variety of polar monomers. In this contribution, we decide to investigate the influence of chelate ring size on the properties of phosphine-sulfonate palladium catalysts. As such, a series of phosphine-sulfonate ligands and the corresponding seven-membered ring Pd(II) complexes [ κ 2-( P , O )-2-(CH2- P R1R2)-4-methylphenyl-sulfonato]Pd(Me) (DMSO) ( Pd1 , R1=R2=Cy, Pd2 , R1=R2= o -MeO-C6H4; Pd3 , R1=Ph, R2=2-[2,6-(MeO)2C6H3]C6H4; DMSO=dimethyl sulfoxide) were designed, prepared and characterized. These palladium complexes are moderately active when they were applied in ethylene polymerization and copolymerizations with methyl acrylate and butyl vinyl ether. However, their properties are greatly reduced from those of the classic six-membered ring phosphine-sulfonate palladium complex Pd2 ′. The experimental results indicate that the bigger chelate ring size can increase the ligand flexibility and damage the catalytic properties for the phosphine-sulfonate type palladium catalysts.