The novel binuclear, oxygen-bridged, bimetallic complexes of the general formula (I): [(LM1R1)(Cp2M2R2)](μ-O)  (I) are suitable as polymerization catalysts for olefin polymerization. (M1=Al, Ge, Zr or Ti; M2=Zr, Ti or Hf; Cp=cyclopentadienyl; R1, R2=methyl, ethyl, i-propyl, t-butyl, halogen, phenyl, alkylphenyl, SiMe3; L=a bidentate, doubly heteroatom-coordinated organic chemical ligand, which together with the metal M1 forms a 5 or 6-membered ring.) They display very good catalytic activities, good operating lives, and require little cocatalyst.