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 o f conformers by virtue of the relative orientation of the trisulfide s trap. 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. Th e trisulfides were converted to the polymers [(RC(5)H(3))(2)FeS2](n) u pon desulfurization with Bu(3)P, which was shown by P-31 NMR spectrosc opy to be converted to Bu(3)PS. The rate of this desulfurization incre ases with the polarity of the reaction solvent. GPC measurements indic ated that the t-Bu- and (t-Bu)(2)-substituted polymers are polydispers e with M(n) = 3700 (M(w) = 26000) and M(n) = 2400 (M(w) = 19000), resp ectively. The soluble ferrocenylene persulfide polymers undergo revers ible electrochemical oxidation in two steps, separated by 290 mv. The first oxidation potential is similar to that for the trisulfide monome r 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 c an be reoxidized (I-2) to the polymer, sulfurized (S-8) to give the tr isulfide, and selenized (Se-8) to give (t-Bu)(2)fcS(2)Se.