REDOX BEHAVIOR OF FERROCENE DERIVATIVES .7. CHALCOGEN-BRIDGED TRINUCLEAR AND TETRANUCLEAR FERROCENES

The electrochemical behaviour of the trinuclear and tetranuclear chalc ogen-bridged ferrocenes Fc-E-(fc)-E-Fc and Fc-E-(fc)-E-E-(fc)-E-Fc (Fc =(eta(5)-C5H5)Fe(eta(5)-C5H4)- (ferrocenyl); fc = -(eta(5)-C5H4)Fe(eta -C5H4)- (1,1'-ferrocenediyl); E = S, Se or Te) has been studied in dic hloromethane solution. In the trinuclear complexes, the expected rever sible one-electron oxidation of each ferrocene unit takes place throug h two nearly overlapping one-electron steps followed by a one-electron process at higher potential. It is assumed that the first two-electro n step corresponds to almost simultaneous electron removals from the t erminal, non-interacting ferrocenyl units, whereas the second process is centred on the central ferrocene. In the tetranuclear species, the oxidation occurs through a single two-electron process, again centred on the terminal ferrocenyl units, followed by two separate one-electro n steps centred on the inner dichalcogen-bridged diferrocene unit,