Synthesis and structure of some (E)-ferrocene-methylenecycloalkanones and their benzylidene analogs

E-2-ferrocenemethylene-and E,E-diferrocenemethylenecycloalkanones as well as partial benzylidene analogues of the latter were synthesized by base-catalyzed Claisen-Schmidt condensation of ferrocenecarboxaldehyde with cyclopentanone, cyclohexanone, cycloheptanone and E-2-(4'-X-benzylidene)cycloalkanones. The stereostructure (configuration and conformation) and the electronic properties (conjugation of the enone moiety and the aromatic rings) of the compounds were studied by IR, 1 H and 13 C NMR methods. The spectroscopic properties of the ferrocene derivatives were compared with those of the respective benzylidene analogues.