SYNTHETIC, STRUCTURAL AND ELECTROCHEMICAL STUDIES ON SOME DOUBLY BRIDGED TRICHALCOGEN [3.3]FERROCENOPHANES

The novel doubly bridged trichalcogen compounds pentathia-10-selena[3. 3](1,1')(2,2')ferrocenophane 1 and its 1,3,9,11-tetrathia-2,10-diselen a analogue have been prepared by disruption of the trisulfur bridges i n ,3,9,10,11-hexathia[3.3](1,1')(2,2')ferrocenophane with lithium alum inium hydride followed by reformation of the bridges using selenium di chloride. The crystal structure of 1 has been determined and indicates a chair-chair conformation of the trichalcogenide linkages, which is the most populous conformeric form in solution. Electrochemistry of va rious trichalcogen-bridged metallocenophanes indicates chemical revers ibility of their redox changes. One-electron removal of the ferrocene systems is shown to be more difficult on introduction of first, one an d then two, trichalcogen bridging groups and redox potentials decrease upon substitution of electron-withdrawing sulfur atoms for less withd rawing selenium atoms.