Transition metal complexes

Transition metal complexes of the formula (Ia) or (Ib),in which the substituents and indices have the following meanings:M is titanium, zirconium, hafnium, vanadium, niobium or tantalum or an element of the third subgroup of the Periodic Table or of the lanthanoids,X is fluorine, chlorine, bromine, iodine, hydrogen, C1-C10-alkyl, C6-C15-aryl, alkylaryl having 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical, -OR5 or -NR5R6,n is 1, 2 or 3, where n is the valency of M minus the number 2,Z is a three-way bridge andA and A1 are two-way bridges.Process for preparing the transition metal complexes, compounds which are used as intermediates for their preparation, the use of the transition metal complexes for polymerizing olefins, processes for polymerizing olefins, homo- or copolymers of ethylene or of propylene with other C2-C12-alk-1-enes, their use for preparing films, fibers or moldings and the films, fibers or moldings made of these polymers.