Side-Arm Control in Phosphine-Sulfonate Palladium- and Nickel-Catalyzed Ethylene Polymerization and Copolymerization

A series of phosphine-sulfonate ligands bearing various side-arm substituents were designed and prepared. The corresponding Pd­(II) complexes [κ2-(P,O)-2-(PPhAr)-1-benzenesulfonato]­Pd­(Me)­(dmso) (Pd1, Ar = o-MeO-C6H4; Pd2, Ar = o-PhO-C6H4; Pd3, Ar = o-(2,6-Me2-C6H3)­O-C6H4; Pd4, Ar = o-PhSO2-C6H4) and Ni­(II) complexes [κ2-(P,O)-2-(PPhAr)-1-benzenesulfonato]­NiPh­(PPh3) (Ni1, Ar = o-MeO-C6H4; Ni2, Ar = o-PhO-C6H4; Ni3, Ar = o-(2,6-Me2-C6H3)­O-C6H4; Ni4, Ar = o-PhSO2-C6H4) were prepared and applied in ethylene polymerization and ethylene–polar monomer copolymerization. Catalysts Pd2, Pd3, Ni2, and Ni3 are moderately active in ethylene polymerization (activity up to 8.7 × 105 g mol–1 h–1), generating polyethylene with high molecular weights (M n up to 105100) and high melting temperatures (T m up to 131.6 °C). The two palladium catalysts can also initiate efficient copolymerization of ethylene with methyl acrylate, allyl cyanide, and allyl acetate. Most importantly, high copolymer molecular weights (M n between 21600 and 82500) and high polar monomer incorporation ratios (between 6.1% and 15.2%) could be achieved simultaneously in this system. This side-arm strategy is highly effective in modulating the properties of the phosphine-sulfonate palladium and nickel catalysts.