Phase and redox shifted four iron/four sulfur clusters: fluorous analogs of metalloenzyme cofactors. Issue 45 (30th July 2015)

• Record Type: Journal Article
• Authors: Zhang, Cheng-Pan; Xi, Zhenxing; Mueller, Kory M.; Holliday, Bradley J.; Bazzi, Hassan S.; Gladysz, John A.
• Is Part Of: Dalton transactions. Volume 44:Issue 45(2015)
• Page Start: 19615
• Page End: 19624
• Publication Date: 2015-07-30
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c5dt01959a
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The title compounds, [Q]2 [Fe4 S4 (S(CH2 ) n Rf8 )4 ], feature dianions with four fluorous thiolate ligands and cations that are non-fluorous, "light fluorous", or "heavy fluorous"; fluorous/organic partition coefficients can reach >93 : <7. Abstract : Reactions of (1) [Q]2 [Fe4 S4 (SC(CH3 )3 )4 ] and the fluorous thiols HS(CH2 ) n Rf8 ( n = 2, 3; Rf8 = (CF2 )7 CF3 )), or (2) [Na]2 [Fe4 S4 (S(CH2 ) n Rf8 )4 ] ( n = 2, 3) and [PhCH2 P((CH2 )3 Rf6 )3 ][Br] or [PPN][Cl] (PPN = Ph3 PNPPh3 ), give the title compounds [Q]2 [Fe4 S4 (S(CH2 ) n Rf8 )4 ], comprised of a fluorous dianion and in some cases fluorous cations, with (1) Q/ n = Ph4 P/2 (4, 67%), Ph4 P/3 (5, 67%), Me4 N/3 (69%), and Ph3 P(CH2 )2 Rf6 /2 (73%) or (2) PhCH2 P((CH2 )3 Rf6 )3 /2 (14, 39%), PhCH2 P((CH2 )3 Rf6 )3 /3 (15, 63%), and PPN/2 (36%). The educt [Ph3 P(CH2 )2 Rf6 ]2 [Fe4 S4 (SC(CH3 )3 )4 ] is in turn prepared from FeCl3, HSC(CH3 )3 /CH3 ONa, and [Ph3 P(CH2 )2 Rf6 ][I], and the educts [Na]2 [Fe4 S4 (S(CH2 ) n Rf8 )4 ] from [Na]2 [Fe4 S4 (SC(CH3 )3 )4 ] and HS(CH2 ) n Rf8 . 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 for5 ). The singly fluorous salts are soluble in organic solvents of moderate polarity, but not in fluorous solvents. The doubly fluorous salts14, 15 are soluble in all fluorous solvents assayed, with partition coefficients of >99.65 : <0.35 (CF3 C6 F11 /toluene) and 93.2–93.1 : 6.9–6.8 (FC-72/THF). Cyclic voltammograms carried out using a platinum working microelectrode show that4 is 0.08 V thermodynamically easier to reduce than5 .