Bis(ferrocenylsilyl)thiophenes and ferrocenylene (silylene) thiophene oligomers

The reaction between 1,1 '-dilithioferrocene and 2,5-bis(chlorodimethylsily l)thiophene (I), leads to a series of cyclic oligomers of basic formulation [Fc-SiMe2-TH-SiMe2](n) (II); Fc = (eta(5)-C5H4)(2)Fe, TH = C4H2S. The mate rial n = 2, IIa, has been completely characterized by spectroscopic and sin gle crystal X-ray diffraction. Cyclic voltammetric analysis of IIa illustra tes two reversible redox processes, indicating a significant interaction be tween the two ferrocenylene units despite the 5 atom bridge. By comparison, the monomeric analog Fc-SiMe2-TH-SiMe2-Fc (III), Fc = (eta(5)-C5H5)Fe(eta( 5)-C5H4), prepared from the reaction of mono-lithioferrocene with I, exhibi ts a single redox process, even though there is the same bridge between the two Fe centers. (C) 2000 Elsevier Science Ltd All rights reserved.