tert-Butyl-Substituted Poly(ferrocenylene persulfides)

The trithiaferrocenophanes (RC[sub 5]H[sub 3])[sub 2]FeS[sub 3] (where R = t-Bu, H) were prepared by dilithiation of the t-Bu-substituted ferrocenes followed by treatment with elemental sulfur. t-BufcS[sub 3] was obtained as the 1,3,1[prime]-isomer. This chiral compound exists in solution as a 1:1 mixture of conformers by virtue of the relative orientation of the trisulfide strap. The species (t-Bu)[sub 2]fcS[sub 3] was obtained as the 1,3,1[prime],4[prime]-isomer, as established by [sup 1]H NMR measurements and X-ray crystallography. The trisulfides were converted to the polymers [(RC[sub 5]H[sub 3])[sub 2]FeS[sub 2]][sub n] upon desulfurization with Bu[sub 3]P, which was shown by [sup 31]P NMR spectroscopy to be converted to Bu[sub 3]PS. The rate of this desulfurization increases with the polarity of the reaction solvent. GPC measurements indicated that the t-Bu- and (t-Bu)[sub 2]-substituted polymers are polydisperse with M[sub n] = 3700 (M[sub w] = 26000) and M[sub n] = 2400 (M[sub w] = 19000), respectively. The soluble ferrocenylene persulfide polymers undergo reversible electrochemical oxidation in two steps, separated by 290 mV. 36 refs., 10 figs., 4 tabs.