A convenient ligand exchange pathway to [2Fe–2S] ferredoxin analogues

Abstract

The benzanellated analogues (NEt(4))(2)[Fe(2)S(2)(indolate)(4)] (2) and (NEt(4))(2)[Fe(2)S(2)(carbazolate)(4)] (3) of the previously reported parent (NEt(4))(2)[Fe(2)S(2)(pyrrolate)(4)] cluster (1) were synthesized and characterized spectroscopically. In contrast to 1 and 3, compound 2 can be applied as a versatile precursor in ligand exchange reactions with various thiophenols affording the thiophenolate-coordinate [2Fe-2S] clusters. Heteroaromatic thiols and chelating biphenols are suitable substrates in this conversion as well, providing a convenient access to a variety of new [2Fe-2S] ferredoxin analogues and related complexes. Several new S- and O-coordinate [2Fe-2S] clusters have been prepared and fully characterized, including five X-ray crystal structures.

Tuning Electronic Properties of Biomimetic [2Fe‐2S] Clusters by Ligand Variations

“…Clusters 1 and 3 were synthesized by standard salt metathesis reactions, starting from (NEt 4 ) 2 [Fe 2 S 2 Cl 4 ], [10] whereas 2 was more conveniently obtained via a ligand exchange pathway, starting from the indolate-ligated precursor (NEt 4 ) 2 [Fe 2 S 2 (indolate) 4 ] [11] (the existence of 2 was previously mentioned in the literature, [12] but neither a synthetic procedure nor any spectroscopic data were reported). An alternative synthesis of 1 by using the ligand exchange approach is possible as well and is described in the Experimental Section.…”

“…Temperature-dependent magnetic susceptibilities of powdered samples were measured by using a SQUID magnetometer (MPMS-5, Quantum Design) at 0.5 T. Cyclic voltammetry was performed with a potentiostat/galvanostat Perkin-Elmer Model 263A with a glassy carbon working electrode and platinum reference and counterelectrodes in MeCN/0. [11] 3,3Ј,5,5Ј-tetrachloro-2,2Ј-dithio-1,1Ј-biphenyl, 2,2Ј-dithio-1,1Ј-biphenyl and 3,3Ј,5,5Ј-tetrakis-tert-butyl-2,2Ј-dithio-1,1Ј-biphenyl were synthesized according to reported methods. [9] All other chemicals were used as purchased.…”

N‐Coordinated [2Fe–2S] and [4Fe–4S] Clusters: Synthesis, Structures and Spectroscopic Characterisation

“…[3] Complexes of two other ligands, indole and carbazole, [4] have been characterised spectroscopically, but could not be obtained in crystalline form. Since the use of suitably substituted heterocycles was expected to favour crystallisation, 2-methylindole was chosen as a ligand for [2Fe-2S] cluster synthesis.…”

“…[2] Besides oxygen, being the lower homologue of sulfur, it is mainly nitrogen that plays an important role as donor to biological Fe/S clusters. Some biomimetic [2Fe-2S] clusters with pure N-donor ligation, both monodentate [3,4] and bidentate, [5,6] have been reported to date. Yet this has not been the case for [4Fe-4S] clusters [7,8] with the exception of the recent characterisation of an all-ferric [4Fe-4S] 4+ cluster bearing amide ligands.…”

The competition between chemistry and biology in assembling iron–sulfur derivatives. Molecular structures and electrochemistry. Part II. {[Fe2S2](SγCys)4} proteins

“…In fact, the crystal structures of complexes 1 [261], 2 [259b], 3 [262], 4 [263], 5-7 [264], 8-10 [263], 11 [265] and 12 [266] are available. The redox potentials of the respective reduction processes are reported in Table 29.…”