Process for the preparation of unsymmetric bis(imino) compounds

Process for the preparation of monoimine compounds, wherein a dicarbonyl compound is reacted in an aliphatic, non-aromatic solvent with aniline. Monoimine compounds having electron-withdrawing substituents in the ortho position and unsymmetric bis(imino) compounds and unsymmetric iron complexes prepared therefrom and the use thereof in the polymerization of olefins.