A new method for the synthesis of the mixed-ligand compound FeCpCp' (w
here Cp' denotes the pentamethyl cyclopentadienyl group) is described
from the reaction of a solution of NaCp' and LiCp with FeCl2 in THF. T
he mixture of products includes FeCp(2), FeCpCp' and FeCp(2)' in appro
ximately a 1 : 3 : 1 mole ratio. Partial oxidation of the mixture lead
s to preferential precipitation of the ferricinium salts of the deriva
tives with the most negative reduction potentials. Subsequent treatmen
t with a reducing agent regenerates the ferrocenes. Implementation of
a couple of redox cycles allows the isolation of pure samples of each
product, including FeCpCp'. Extension of the method to the preparation
of other unsymmetrical ferrocenes is straightforward so long as there
is a modest spread in the reduction potentials of the components. The
development of new synthetic methods is worthwhile because substitute
d ferrocenes are useful reagents in studies of electron-transfer proce
sses. The method described herein is attractive because it is quite si
mple and adaptable to large-scale preparations.