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Author(s):Compton, David Lee
Doctoral Committee Chair(s):Rauchfuss, Thomas B.
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Inorganic
Chemistry, Polymer
Abstract:The trithiaferrocenophanes $\rm (RC\sb5H\sb3)\sb2FeS\sb3$ (where R = t-Bu, H) were prepared by dilithiation of the t-Bu-substituted ferrocenes followed by treatment with elemental sulfur. t-BufcS$\sb3$ was obtained as the 1,3,1$\sp\prime$ isomer. In the case of (t-Bu)$\sb2$fcS$\sb3$, this species was obtained as the $1,3,1\sp\prime ,4\sp\prime$ isomer, as established by $\sp1$H NMR measurements and X-ray crystallography. The trisulfides were converted to the polymers $\rm\lbrack (RC\sb5H\sb3)\sb2FeS\sb2\rbrack\sb{n}$ upon desulfurization with Bu$\sb3$P, which was shown by $\sp{31}$P NMR spectroscopy to be converted to Bu$\sp3$PS. GPC measurements indicated that the (t-Bu)- and (t-Bu)$\sb2$- substituted polymers are polydisperse with $\rm M\sb{n}=3,700\ (M\sb{w}=26,000)\ and\ M\sb{n}=2,400\ (M\sb{w}=19,000)$, respectively. The soluble ferrocenepersulfide 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$\sp{\rm II}$ sites. Reduction of ((t-Bu)$\rm\sb2fcS\sb2\rbrack\sb{\rm n}$ with LiBHEt$\sb3$ gave (t-Bu)$\sb 2fc{\rm S\sb2Li\sb2}$, which can be reoxidized (I$\sb2$) to the polymer, sulfurized (S$\sb8$) to give the trisulfide, and selenized (Se$\sb8$) to give (t-Bu)$\sb2fc{\rm S\sb2Se}$.
The molecular precursor, $\rm (BuC\sb5H\sb3)(C\sb5H\sb4)FeS\sb3$, was prepared by dilithiation of butylferrocene followed by treatment with elemental sulfur and isolated as a 7:1 mixture of the 1,3,1$\sp\prime$ and 1,2,1$\sp\prime$ isomers. This trisulfide was converted to polymer by treatment with PBu$\sb3$. The rate of this desulfurization and the molecular weight of the polymer depends critically on the reaction solvent. Desulfurization of BufcS$\sb3$ in mixed $\rm CH\sb2Cl\sb2$-THF solutions gave polymers with M$\sb{\rm w}$ ranging from 45,000 to 4,000, with lower molecular weight products being favored at high $\rm\lbrack CH\sb2Cl\sb2\rbrack $. Molecular weights for (BufcS$\sb2\rbrack\sb{\rm n}$ were confirmed by light scattering measurements. The polymers photodegrade upon exposure to UV light in air. Deselenization of BufcSe$\sb3$ gave red soluble (BufcSe$\sb2\rbrack\sb{\rm n}$ with only moderate molecular weights and with high polydispersities. The microstructure of this polymer was established by $\sp{77}$Se NMR studies which support the presence of head-to-head, head-to-tail, and tail-to-tail dyads.
Poly(dimethylaminomethylferrocenylene persulfides), $\rm\lbrack (DmamC\sb5H\sb3)(C\sb5H\sb4)FeS\sb2\rbrack\sb{n}$, have been prepared by desulfurization of dimethylaminomethyltrithiaferrocenophane $\rm (DmamC\sb5H\sb3)(C\sb5H\sb4)FeS\sb3$. The desulfurization of THF solutions of DmamfcS$\sb3$ afforded low molecular weight products with M$\sb{\rm n}$ = 1,100 (M$\sb{\rm w}$ = 2,900).
The synthesis and desulfurization of the ansa ferrocenes $\rm C\sb3H\sb6$fcS$\sb3$ and $\rm Me\sb2C\sb2$fcS$\sb3$ were conducted to probe the importance of $\rm C\sb5R\sb5$ ring rotation in the desulfurization-induced polymerizations. Analysis using SEC and FAB mass spectroscopy indicate that the desulfurization of $\rm C\sb3H\sb6$fcS$\sb3$ does not produce oligomers or high molecular weight polymers.
Issue Date:1996
Rights Information:Copyright 1996 Compton, David Lee
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9712237
OCLC Identifier:(UMI)AAI9712237

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