New cyclopalladated complexes (Pd-A, Pd-B, Pd-C) were used as catalysts in ethylene polymerization. All of them show good activity, especially at a temperature of 80 degreesC. The molecular weight and molecular weight distribution obtained correspond to single-site catalysts, producing polymers with narrow molecular weight distribution. The melting points correspond to linear polyethylene. UV-visible spectroscopy studies were used to determine possible polymerization mechanisms. (C) 2004 Elsevier B.V All rights reserved.