title: Phase and redox shifted four iron/four sulfur clusters: fluorous analogs of metalloenzyme cofactors.
abstract: Reactions of (1) [Q]2[Fe4S4(SC(CH3)3)4] and the fluorous thiols HS(CH2)nRf8 (n = 2, 3; Rf8 = (CF2)7CF3)), or (2) [Na]2[Fe4S4(S(CH2)nRf8)4] (n = 2, 3) and [PhCH2P((CH2)3Rf6)3][Br] or [PPN][Cl] (PPN = Ph3P[horiz bar, triple dot above]N[horiz bar, triple dot above]PPh3), give the title compounds [Q]2[Fe4S4(S(CH2)nRf8)4], comprised of a fluorous dianion and in some cases fluorous cations, with (1) Q/n = Ph4P/2 (, 67%), Ph4P/3 (, 67%), Me4N/3 (69%), and Ph3P(CH2)2Rf6/2 (73%) or (2) PhCH2P((CH2)3Rf6)3/2 (, 39%), PhCH2P((CH2)3Rf6)3/3 (, 63%), and PPN/2 (36%). The educt [Ph3P(CH2)2Rf6]2[Fe4S4(SC(CH3)3)4] is in turn prepared from FeCl3, HSC(CH3)3/CH3ONa, and [Ph3P(CH2)2Rf6][I], and the educts [Na]2[Fe4S4(S(CH2)nRf8)4] from [Na]2[Fe4S4(SC(CH3)3)4] and HS(CH2)nRf8. The SCH2(1)H and (13)C NMR signals of these paramagnetic salts appear 8.7-10.3 and 32.3-34.9 ppm downfield from those of the corresponding thiols, but the chemical shifts of other signals are nearly normal. The UV-visible spectra show bands similar to those of non-fluorous analogs (290-298 nm and 406-415 nm; ε = 25 700 and 19 200 M(-1) cm(-1) for ). The singly fluorous salts are soluble in organic solvents of moderate polarity, but not in fluorous solvents. The doubly fluorous salts , are soluble in all fluorous solvents assayed, with partition coefficients of >99.65 : <0.35 (CF3C6F11/toluene) and 93.2-93.1 : 6.9-6.8 (FC-72/THF). Cyclic voltammograms carried out using a platinum working microelectrode show that is 0.08 V thermodynamically easier to reduce than .
authors.affiliation: Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012, USA. gladysz@mail.chem.tamu.edu.
authors.forename: Cheng-Pan
authors.initials: CP
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012, USA. gladysz@mail.chem.tamu.edu.
authors.forename: Zhenxing
authors.initials: Z
authors.lastname: Xi
authors.affiliation: Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA. bholiday@cm.utexas.edu.
authors.forename: Kory M
authors.initials: KM
authors.lastname: Mueller
authors.affiliation: Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, USA. bholiday@cm.utexas.edu.
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: Holliday
authors.affiliation: Department of Chemistry, Texas A&M University at Qatar, P.O. Box 23874, Doha, Qatar. bazzi@tamu.edu.
authors.forename: Hassan S
authors.initials: HS
authors.lastname: Bazzi
authors.affiliation: Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012, USA. gladysz@mail.chem.tamu.edu.
authors.forename: John A
authors.initials: JA
authors.lastname: Gladysz