A straightforward synthetic methodology to prepare ansa-monocyclopentadienyl-imino-pyridine dichloro metal derivatives of the type MLCl2(THF) {M = Y, Sm, Nd} has been developed. Here, we report the syntheses and characterizations of both the ligand and the complexes and the results of some catalytic tests towards olefin polymerization. The most astonishing data come from the influence of both the metal fragments and the co-catalysts used towards the selectivity in butadiene polymerization: in fact, changing these parameters it is possible to range from >99% 1,4 cis-polybutadiene to >99% 1,4 trans-polybutadiene. (C) 2007 Elsevier B.V. All rights reserved.