Mononuclear pyridinyl-imine complexes of palladium containing functionalities attached to the alkyl or aromatic group bonded to the imino nitrogen were prepared and evaluated as potential catalyst precursors for ethylene polymerization. Activated by methylaluminoxane these complexes were found to be efficient ethylene polymerization catalysts. Complexes containing either allyl, styryl and phenol functionalities were found to be more active catalysts than a standard pyridinyl-imine complex containing an unfunctionalized aliphatic substituent. (c) 2005 Elsevier B.V. All rights reserved.