PREPARATION OF ETA(5)-CYCLOPENTADIENYL-ET A(6)-AZOBENZENE IRON(1+) CATIONS

Different methods to prepare eta(5)-cyclopentadienyl- eta(6)-azobenzen es-iron(1 +) have been studied. Because of the weak nucleophilicity an d low solubility of complexed aniline, the reaction between eta(5)-cyc lopentadienyl-eta(6)-aniline-iron(1 +) and nitrosobenzene in acetic ac id is too slow to obtain azo-cationic species in good yield. Addition of nitrosobenzene to deprotonated eta(5)-cyclopentadienyl-eta(6)-anili ne-iron(1 +) in THF leads to a low yield of azo-cationic compound, bec ause of the instability of nitrosobenzene in basic organic media and a partial transformation of complexed aniline. The best results are obt ained upon addition of anilines without electron-withdrawing group to a solution of eta(5)-cyclopentadienyl- eta(6)-nitrosobenzenes-iron(1 ) prepared from the corresponding nitro-cationic compounds in a ''redo x'' cell fitted with two porous electrodes. a(6)-azobenzene-bis(eta(5) -cyclopentadienyliron)(2 +) is obtained directly by electrolysis of co rresponding azoxydicationic compound in a ''redox'' cell.