TERT-BUTYL-SUBSTITUTED POLY(FERROCENYLENE PERSULFIDES)

The trithiaferrocenophanes (RC(5)H(3))(2)FeS3 (where R = t-Bu, H) were prepared by dilithiation of the t-Bu-substituted ferrocenes followed by treatment with elemental sulfur. t-BufcS(3) was obtained as the 1,3,1'-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 speices (t-Bu)(2)fcS(3) was obtained as the 1,3,1',4'-isomer, as established by H-1 NMR measurements and X-ray crystallography. The trisulfides were converted to the polymers [(RC(5)H(3))(2)FeS2](n) upon desulfurization with Bu(3)P, which was shown by P-31 NMR spectroscopy to be converted to Bu(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)(2)-substituted polymers are polydisperse with M(n) = 3700 (M(w) = 26000) and M(n) = 2400 (M(w) = 19000), respectively. The soluble ferrocenylene persulfide polymers undergo reversible electrochemical oxidation in two steps, separated by 290 mv. The first oxidation potential is similar to that for the trisulfide monomer and is thought to correspond to oxidation of alternating Fe centers. The second oxidation converts the remaining Fe-II sites. Reduction of [t-Bu)(2)fcS(2)](n) with LiBHEt(3) gave (t-Bu)(2)fcS(2)Li(2), which can be reoxidized (I-2) to the polymer, sulfurized (S-8) to give the trisulfide, and selenized (Se-8) to give (t-Bu)(2)fcS(2)Se.