A fluorinated LTM catalyst of [bis(N,N'-2-fluorophenylimino)acenaphthene] nickel(II) dibromide was prepared and applied for ethylene polymerization. We established a reasonable hypothesis, highlighting the role of fluorine in ligand structure. In addition, density functional theory (DFT) studies have been applied to strengthen our propositions. DFT calculations of the beta-agostic cationic species at room temperature and 75 degrees C suggest that the beta-agostic structure for the latter was destabilized by 19 eV which rendered it less prone to beta-H transfer reactions than the species at room temperature. In addition, a mechanism for the catalyst deactivation for fluorinated alpha-diimine nickel based catalysts has been proposed.