The invention relates to coordination compounds of the general formulae (Ia) to (Ib), wherein M=Ti, Zr, Hf, V, Nb or Ta. The invention also relates to a method for producing the metal complexes and to the use of the complexes so obtained for the polymerization and copolymerization of olefins. For example in suspension polymerization methods, gas phase polymerization methods and bulk polymerization methods ##STR1##