Catalyst components based on ferrocenyl complexes used for olefin polymerisation

An ferrocinium ligand of formula

• wherein Cp is a cyclopentadienyl group, unsubstituted or substituted, with chelating arms,
• wherein X and Y are the same or different with the restriction that at least one Y or X contains at least one chelating group in direct connection with the ferrocinium, the other of Y or X being optionally present and wherein X and/or Y are each independently selected to include atoms O, N, P, S or groups —CR═CR—, —CR═N—, —N═CR— or —C≡C— wherein R is H, alkyl or aryl groups having at most 20 carbon atoms,
• wherein Z and W are each independently selected from alkyl, aryl, heterocycle group or non-heterocycle group containing ether, thioether, phosphine, imine, amine or amide,
• wherein iron has been oxidated with an oxidant capable to oxidate FeII into FeIII but mild enough to preserve the ligand, and
• wherein A− is an anion associated to FeIII.