Polynuclear metallocene complexes incorporating ansa-chromocene and ferrocene units

Novel bimetallic and trimetallic complexes containing ansa-chromocene units have have been synthesized by a ligand substitution approach. The carbonyl ligands of the corresponding ansa-chromocene carbonyl complexes were substituted by the mono- and diisocyanide species ferrocenylisocyanide, ferrocenyldiisocyandie, and 1,4-phenylene diisocyanide in order to form polymetallic complexes that might exhibit mixed valence behavior. The heteronuclear complexes containing a ferrocene unit show a remarkable stability against thermolysis and photolysis. Cyrstallographic data show that the C-N-C bond angles and Cr-C bond distances of these species follow the trend of other ansa-chromocene isocyanides that show a moderate dependence of the Cr 2+/3+ redox potential on the substituents of the isocyanide groups. In contrast, the heteronuclear complexes do not follow such a trend in respect to their electronic properties. Interestingly, these complexes can modulate the electron density at the Cr metal centers, which enables them to keep their redox potentials constant.