Seven transition-metal complexes of general formula RC(CH2NPR'(3))(3))MX2 based on new tripodal iminophosphorane ligands were investigated as initiators for the oligomerization of ethylene in the presence of aluminum co-catalysts using high-throughput techniques. In all cases, ethylene consumption peaked at ca. 30 degrees C and was not drastically affected by varying the nature of the metal (M = Ni, Fe, Pd, Cu), the aluminum co-catalyst (MMAO, Et2AlCl, or EtAlCl2) or the substituents of the tris(iminophosphorane) ligand (R = Me, Ph; R'= cyclopentyl, Ph). Structural modifications of the organometallic complexes, either at the metal center or within the tripodal ligand, however, had a significant impact on the oligomer distribution obtained. In particular, Pd-based catalyst (PhC(CH2NPPh3)(3))PdCl2 displayed an excellent selectivity toward hexene formation. (c) 2007 Elsevier B.V. All rights reserved.