Architectural Mimics of FeFe-Hydrogenase H-Cluster: Synthesis, Characterization and Electrochemical studies

The utilization of H2 for energy was probably a crucial feature of very early life on this planet. Therefore, the tendency to find a proper way to produce H2 is an interest area for research in the scientific community. In Fact, the nature has high ability to catalyze the reversible reduction of protons to molecular hydrogen through metalloenzymes known as hydrogenases. These metalloenzymes can be classified into [Fe]-hydrogenases (Hmd), [NiFe]-hydrogenases and [FeFe]-hydrogenases. In the case of the latter, the reaction takes place at the “H-cluster”, which consists of an [4Fe4S] cubane attached through a cysteinyl residue to a butterfly [2Fe2S] sub-cluster. The [2Fe2S] unit features a bridging azadithiolato ligand as well as biologically unusual CO and CN- ligands. Over the past decades, numerous synthetic models which mimic the H-cluster have been reported to provide a better understanding of the structure and function of the active site of the enzyme-mimic models. Moreover, these models have been extended to diiron complexes containing diselenato and ditellurato ligands

Dual Function of β ‐Hydroxy Dithiocinnamic Esters: RAFT Agent and Ligand for Metal Complexation

Abstract The reversible addition‐fragmentation chain‐transfer (RAFT) process has become a versatile tool for the preparation of defined polymers tolerating a large variety of functional groups. Several dithioesters, trithiocarbonates, xanthates, or dithiocarbamates have been developed as effective chain transfer agents (CTAs), but only a few examples have been reported, where the resulting end groups are directly considered for a secondary use besides controlling the polymerization. Herein, it is demonstrated that β ‐hydroxy dithiocinnamic esters represent a hitherto overlooked class of materials, which are originally designed for the complexation of transition metals but may as well act as reversible CTAs. Modified with a suitable leaving group (R‐group), these vinyl conjugated dithioesters indeed provide reasonable control over the polymerization of acrylates, acrylamides, or styrene via the RAFT process. Kinetic studies reveal linear evolutions of molar mass with conversion, while different substituents on the aromatic unit has only a minor influence. Block extensions prove the livingness of the polymer chains, although extended polymerization times may lead to side reactions. The resulting dithiocinnamic ester end groups are still able to form complexes with platinum, which verifies that the structural integrity of the end group is maintained. These findings open a versatile new route to tailor‐made polymer‐bound metal complexes

Electrochemical and Computational Insights into the Reduction of [Fe₂(CO)₆{<i>µ</i>-(SCH₂)₂GeMe₂}] Hydrogenase H-Cluster Mimic

The electrochemical reduction of the complex [Fe2(CO)6{&#181;-(SCH2)2GeMe2}] (1) under N2 and CO is reported applying cyclic voltammetry. Reduction of complex 1 in CO saturated solutions prevents the possible release of CO from the dianion 12&#8722;, while the latter reacts with additional CO forming a spectroscopically uncharacterized product P1. This product undergoes a reversible redox process at E1/2 = &#8722;0.70 V (0.2 V∙s&#8722;1). In this report, the structure of the neutral complex 1, isomers of dianionic form of 1, and P1 are described applying DFT computations. Furthermore, we propose reaction pathways for H2 production on the basis of the cyclic voltammetry of complex 1 in presence of the strong acid CF3SO3H

Ligand effects on structural, protophilic and reductive features of stannylated dinuclear iron dithiolato complexes

The synthesis and characterization of Fe2(CO)5(L){μ-(SCH2)2SnMe2} (L = PPh3 (2) and P(OMe)3 (3)) derived from the parent hexacarbonyl complex Fe2(CO)6{μ-(SCH2)2}SnMe2 (1) are reported. Whereas 1 exhibits a unique planar structure, X-ray crystallography showed that the apical orientation of L in complexes 2 and 3 results in a chair/boat conformation of the Fe2S2C2Sn fused six-membered rings, which is typical for diiron dithiolato complexes. In solution, NMR and FTIR spectroscopic techniques provide evidence for a dynamic process of apical–basal site exchange of the ligand L in 2 and 3. Protonation experiments on 2 and 3 in MeCN using CF3CO2H, HCl or HBF4·Et2O suggest enhanced protophilicity of the Fe–Fe bond due to the presence of the electron donor ligands L as well as the stannylation effect. While the carbonyl ligands in 2 stretch at lower wavenumbers ν(CO) than those in 3, the cyclic voltammetric reduction of 2 unpredictably occurs at less negative potential than that of 3. In contrast to 1, the presence of PPh3 and P(OMe)3 in 2 and 3, respectively, allows protonation prior to reduction as shown by FTIR spectroscopy and cyclic voltammetry

Synthesis, characterization and electrochemical investigations of heterocyclic-selenocarboxylate iron complexes

cited By 2International audienceSelenocarboxylato complexes of iron containing heterocyclic group of the general formula CpFe(CO)2SeCO-het [het = 2-C4H3S (1), 2-C4H3O (2), -CH2-2-C4H3S (3)] were prepared from the reaction of iron selenide, (μ-Se)[FeCp(CO)2]2 and the corresponding heterocyclic acid chlorides. These complexes have been characterized by elemental analysis, UV-Vis, IR and 1H NMR spectroscopic techniques. The X-ray structure of 1 is determined and its electrochemical behavior has been described in details applying cyclic voltammetry. © 2016 Elsevier B.V