Two bis(imino)pyridine cobalt complexes have been synthesized, the dichlorido-(2,6-bis[1-(phenylimine)ethyl] pyridine) cobalt(II) ([Co-NNNPhH]) and the dichlorido-(2,6-bis[1-(2-trifluoromethyl-4-fluorophenylimine)ethyl] pyridine) cobalt(II) ([Co-NNNPhF]) and used as catalyst precursor in association with methylaluminoxane (MAO) as cocatalyst in propylene oligomerization. The presence of a fluorine group in [Co-NNNPhF] have been investigated and compared to those of [Co-NNNPhH] regarding the catalytic properties in propylene oligomerization and the structure of the complexes. The correlation of the catalytic properties of the cobalt complexes and their structures have been evidenced.