Abstract: The invention relates to a catalyst system comprising a support in which transition metal cations or uncharged transition metal atoms are distributed. The system further comprises one or more separately added ligands which are capable of forming a coordinate or covalent bond with the transition metals. The catalyst system is produced by replacing metal ions present in a support by transition metal ions. The transition metal ions can optionally be reduced. One or more ligands which are capable of forming a coordinate or covalent bond with the transition metal or metals are subsequently added. The catalyst is used for the polymerization of olefins.