title: A [4Fe-4S] cluster dimer bridged by bis(2,2':6',2''-terpyridine-4'-thiolato)iron(II).
abstract: The use of 2,2':6',2''-terpyridine-4'-thiol (tpySH) was explored as a bridging ligand for the formation of stable assemblies containing both [4Fe-4S] clusters and single metal ions. Reaction of tpySH (2 equiv) with (NH4)2Fe(SO4)(2).6H2O generated the homoleptic complex [Fe(tpySH)2](2+), which was isolated as its PF6(-) salt. The compound could be fully deprotonated to yield neutral [Fe(tpyS)2], and the absorption spectrum is highly dependent on the protonation state. Reaction of [Fe(tpySH)2](PF6)2 with the new 3:1 site-differentiated cluster (n-Bu4N)2[Fe4S4(TriS)(SEt)] yielded the first metal-bridged [4Fe-4S] cluster dimer, (n-Bu4N)2[{Fe4S4(TriS)(mu-Stpy)}2Fe]. Electrochemical studies indicate that the [4Fe-4S] clusters in the dimer act as independent redox units, while UV-vis spectroscopy provides strong evidence for a thioquinonoid electron distribution in the bridging tpyS(-) ligand. TpySH thus acts as a directional bridging ligand between [4Fe-4S] clusters and single metal ions, thereby opening the way to the synthesis of larger, more complex assemblies.
authors.affiliation: Chemical Biology & Organic Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Erwin P L
authors.initials: EP
authors.lastname: van der Geer
authors.forename: Gerard
authors.initials: G
authors.lastname: van Koten
authors.forename: Robertus J M
authors.initials: RJ
authors.lastname: Klein Gebbink
authors.forename: Bart
authors.initials: B
authors.lastname: Hessen
mesh_terms: D003432:Cross-Linking Reagents / Q000737:chemistry*; D019281:Dimerization; D005296:Ferrous Compounds / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D021241:Spectrometry, Mass, Electrospray Ionization; D013053:Spectrophotometry
chemical_list: D003432:Cross-Linking Reagents; D005296:Ferrous Compounds; D007506:Iron-Sulfur Proteins; C529201:bis(2,2'-6',2''-terpyridine-4'-thiolato)iron(II)