Biomedical subjects
Thomas B. Rauchfuss
Publications and source records attributed to Thomas B. Rauchfuss.
Diiron Azadithiolates as Models for the Iron-Only Hydrogenase Active Site: Synthesis, Structure, and Stereoelectronics This research was supported by the NIH and the Centre Universitaire et Régional de Ressources Informatiques of ULP and CNRS.
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Sulfido-Persulfido Equilibria in Sulfur-Rich Metal Clusters: The Case of (C(5)Me(5))(3)RhRu(2)S(4)(2+).
The reaction of [(C(5)Me(5))M(MeCN)(3)](PF(6))(2) with (C(5)Me(5))(2)Ru(2)S(4) gives the cluster compounds [(C(5)Me(5))(3)MRu(2)S(4)(MeCN)](PF(6))(2), 1(PF(6))(2) (M = Rh) and 3(PF(6))(2) (M = Ir). Crystallographic studies of 1(PF(6))(2) show that the dication consists of an asymmetric RhRu(2)S(4) core containing an isosceles triangle of metal atoms with a Ru-Ru bond of 2.88 Å. The three metal atoms are joined by two &mgr;(3)-eta(1):eta(2):eta(1-)S(2) units, each persulfide being monodentate toward Rh. NMR studies show that 1(2+) is stereochemically nonrigid such that the two Ru(C(5)Me(5)) resonances coalesce at higher temperatures. The dynamic processes involving 1(2+) are unaffected by added (C(5)Me(5))Rh(MeCN)(3)(2+), ruling out dissociation of the (C(5)Me(5))Rh center. Exchange of the (C(5)Me(5))Ru sites in [(C(5)Me(5))(2)(C(5)Me(4)Et)RhRu(2)S(4)(MeCN)](PF(6))(2), 2(PF(6))(2), is associated with coalescence of the pairs of C(5)Me(4)Et resonances, suggesting that the dynamics in 1(2+) involve racemization. It is proposed that these dynamics proceed via the "base-free" intermediate [(C(5)Me(5))(3)RhRu(2)S(4)](2+), wherein one S-S bond has been cleaved. Solutions of 1(2+) react with acetone to give the S-acetonyl derivative [(C(5)Me(5))(3)RhRu(2)S(3)(SCH(2)COCH(3))]PF(6), 4(PF(6)). This species, which is not fluxional on the NMR time scale, is a rare example of a metal sulfido cluster with a trigonal prismatic M(3)S(3) core. There is one metal-metal bond of 2.75 Å between the two Ru atoms, spanned by the acetonylthio ligand. The M-S distances are nearly equivalent at 2.33 Å while the S-S bonding distance is 2.12 Å. This reaction is reversed by acid to give 1(2+) and acetone.
Iron Sulfido Derivatives of the Fullerenes C(60) and C(70).
Toluene solutions of C(60) react upon UV irradiation with Fe(2)S(2)(CO)(6) to give C(60)[S(2)Fe(2)(CO)(6)](n)() where n = 1-6. C(60)[S(2)Fe(2)(CO)(6)](n)() where n = 1-3 have been isolated and characterized. Crystallographic studies of C(60)S(2)Fe(2)(CO)(6) show that the S-S bond of the Fe(2) reagent is cleaved to give a dithiolate with idealized C(2)(v)() symmetry. The addition occurred at a 6,6 fusion, and the metrical details show that the Fe(2) portion of the molecule resembles C(2)H(4)S(2)Fe(2)(CO)(6). IR spectroscopic measurements indicate that the Fe(2)(CO)(6) subunits in the multiple-addition species (n > 1) interact only weakly. UV-vis spectra of the adducts show a shift to shorter wavelength with addition of each S(2)Fe(2)(CO)(6) unit. Photoaddition of the phosphine complex Fe(2)S(2)(CO)(5)(PPh(3)) to C(60) gave C(60)[S(2)Fe(2)(CO)(5)(PPh(3))](n)(), where n = 1-3. (31)P{(1)H} NMR studies show that the double adduct consists of multiple isomers. Photoaddition of Fe(2)S(2)(CO)(6) to C(70) gave a series of adducts C(70)[S(2)Fe(2)(CO)(6)](n)() where n = 1-4. HPLC analyses show one, four, and three isomers for the adducts, respectively.