Linear copolymers of ethylene and acrylonitrile were prepared using palladium complexes bearing phosphine-sulfonate bidentate ligands. Acrylonitrile units located in the linear polyethylene backbones were detected for the first time by C-13 NMR spectroscopy. Catalyst systems employing isolated palladium complexes such as 3 showed much higher activity for the copolymerization than the in situ generation procedures, and molecular weight of the copolymers and acrylonitrile incorporation were dependent on the palladium complexes. Obtained linear copolymers of ethylene and acrylonitrile melt at higher temperature than branched copolymers.