A. Tarraga et al., Synthesis and electrochemical study of novel oxazolo-ferrocene derivativesdisplaying redox-switchable character, TETRAHEDRON, 57(31), 2001, pp. 6765-6774
A synthetic procedure has been developed to prepare new oxazolo-ferrocene l
igands. The method, which allows the formation of homobimetallics oxazole-f
errocenes 4-7 containing two oxazole rings in the conjugation chain, is bas
ed on the aza-Wittig reaction of alpha -azidoacetyl ferrocene 1 with diacyl
chlorides and triphenylphosphine. This route has the characteristic of tun
ing the size and shape of the spacer which could have aliphatic, aromatic,
and heteroaromatic nature. Likewise, the reaction of 1, 1 1-bis(alpha -azid
oacetyl) ferrocene 3 with aroyl chlorides in the presence of triphenylphosp
hine affords ferrocene ligands 11 linked to two oxazole rings. The stable s
olids were thoroughly characterized by spectroscopic means and electrochemi
cal methods. Ligands 4-7 showed chemically reversible oxidations with two o
ne-electron processes, indicating that the iron centres do not electronical
ly communicate with each other. Electrochemical investigations reveal the r
espective ferrocene-ferrocenium redox couples of the ligands 11 and 14 are
perturbed to a more positive potentials upon protonation and co-ordination
of Zn(II) guest cation. (C) 2001 Elsevier Science Ltd. All rights reserved.