Synthesis and coordination behaviour of 1H-1,2,3-triazole-4,5-dithiolates

The preparative access to and first group 10 metal complexes of novel 1H-1,2,3-triazole-4,5-dithiolate ligands (tazdt^2-) are reported. A set of S-protected 1H-1,2,3-triazole-4,5-dithiol derivatives with R¹ = 2,6-dimethylphenyl (Xy) or benzyl (Bn) at N1 and with R² = Bn or trimethylsilylethyl (TMS-ethyl) at both S atoms were synthesized by a 1,3-dipolar cycloaddition catalysed by either Ru(II) or Cu(I). Extensive investigations on the removal of the protective groups resulted the reductive removal of benzyl groups to be superior in isolating the free 4,5-dithiols of R¹N₃C₂(SH)₂ with R¹ = Xy (H₂-8) or Bn (H₂-9). Coordination of these ligands led to the formation of the metal complexes [(η⁵-C₅H₅)₂Ti(8)], [Ni(dppe)(8)], [Ni(dppe)(9)], [Pd(dppe)(9)] {dppe = bis(diphenylphosphanyl)ethane} and homoleptic (NBu₄)_n[Ni(8)₂] (n = 1, 2). All complexes were fully characterized including structure determination by single crystal XRD. The electronic properties of the Ni and Pd complexes were determined by cyclic voltammetry, UV/vis and EPR spectroscopy supported by DFT calculations. According to the spectral and electrochemical data, the tazdt^2- complexes resemble the corresponding benzene-1,2-dithiolate (bdt^2-) type compounds reflecting the restricted influence of the electron-withdrawing N₃ moiety in the backbone. DSC-TGA measurements with [(η⁵-C₅H₅)₂Ti(8)] and [Ni(dppe)(8)] indicate a well-defined thermal process involving simultaneous elimination of both N₂ and CS.

Di-, tri- and tetraphosphine-substituted Fe/Se carbonyls: Synthesis, Characterization and electrochemical properties

The active sites of [FeFe]-hydrogenase promoted by Fe/E (E=S, Se) clusters have attracted considerable interest due to their significance for understanding the interconversion of hydrogen with protons and electrons. As...

Dithiol-Dithione Tautomerism of 2,3-Pyrazinedithiol in the Synthesis of Copper and Silver Coordination Compounds

A promising strategy for new electrically conductive coordination polymers is the combination of d¹⁰ metal ions, which tolerate short metal···metal distances, with dithiolene linkers, known for their "non-innocent" redox behavior. This study explores the coordination chemistry of 2,3-pyrazinedithiol (H₂pdt) toward Cu⁺ and Ag⁺ ions, highlighting similarities and differences. The synthetic approach, starting with the fully protonated ligand, allowed the isolation of a homoleptic bis(dithiolene) complex with formal Cu^I atoms, [Cu(H₂pdt)₂]Cl (1). This complex was further transformed to a 1D coordination polymer with short metal···metal distances, ^1D[Cu(Hpdt)] (2^Cu). The larger Ag⁺ ion directly built up a very similar coordination polymer, ^1D[Ag(Hpdt)] (2^Ag), without any appearance of an intermediate metal complex. The coordination polymer ^1D[Cu(H₂pdt)I] (4), like complex 1, bears fully protonated H₂pdt ligands in their dithione form. Upon heating, both compounds underwent auto-oxidation coupled with a dehydrogenation of the ligand to form the open-shell neutral copper(II) complex [Cu(Hpdt)₂] (3) and the coordination polymer ^1D[Cu₂I₂(H₂pdt)(Hpdt)] (5), respectively. For all presented compounds, crystal structures are discussed in-depth. Furthermore, properties of 1, 3, and those of the three 1D coordination polymers, 2^Ag, 2^Cu, and 4, were investigated by UV-vis-NIR spectroscopy, cyclic voltammetry, and variable-temperature magnetic susceptibility, and direct current (dc)-conductivity measurements. The experimental results are compared and discussed with the aid of DFT simulations.

A DFT study of structure and electrochemical properties of diiron-hydrogenase models with benzenedithiolato and benzenediselenato ligands

The chalcogen atom substitution in the Fe₂(bdt)(CO)₆ complex results in higher and lower proton affinities of iron and chalcogen atoms, respectively.

Phosphine-substituted Fe–Te clusters related to the active site of [FeFe]-H2ases

Mono-, di-, and tetranuclear phosphine-substituted Fe/Te clusters 1–6 were described.

FeMo Heterobimetallic Dithiolate Complexes: Investigation of Their Electron Transfer Chemistry and Reactivity toward Acids, a Density Functional Theory Rationalization

The electrochemical behavior of complexes [FeMo(CO)₅(κ²-dppe)(μ-pdt)] (1) and [FeMo(CO)₄(MeCN)(κ²-dppe)(μ-pdt)] (2), in the absence and in the presence of acid, has been investigated. The reduction of 1 follows at slow scan rates, in CH₂Cl₂-[NBu₄][PF₆] and acid-free media, an EC_revE mechanism that is supported by cyclic voltammetry (CV) experiments and digital CV simulations. In MeCN-[NBu₄][PF₆], the electrochemical reduction of 1 is the same as in dichloromethane and follows an ECE mechanism at slow scan rates, but with a positive shift of the redox potentials. In contrast, the oxidation of 1 is strongly solvent-dependent. In dichloromethane, the oxidation of 1 is reversible and involves a single electron, while in acetonitrile, it is irreversible at moderate and slow scan rates ( v ≤ ca. 1 V s^-1), and some chemical reversibility is apparent at higher scan rates ( v = 10 V s^-1). Density functional theory calculations revealed that the chemical step in the EC_revE mechanism corresponds to the dissociation of one PPh₂ end of the diphosphine ligand and the transfer of the semibridging CO to the Fe atom, similarly to the mechanism observed in the FeFe analogue complex. However, in the case of 1, the subsequent coordination of the phosphine ligand to the other metal is an unfavorable process.

A mononuclear iron carbonyl complex [Fe(μ-bdt)(CO)2(PTA)2] with bulky phosphine ligands: a model for the [FeFe] hydrogenase enzyme active site with an inverted redox potential

A mononuclear hexa-coordinated iron carbonyl complex [Fe(μ-bdt)(CO)₂(PTA)₂] 1 (bdt = 1,2-benzenedithiolate; PTA = 1,3,5-triaza-7-phosphaadamantane) with two bulky phosphine ligands in the trans position was synthesized and characterized by X-ray structural analysis coulometry data, FTIR, electrochemistry and electronic structure calculations. The complex undergoes a facilitated two-electron reduction 1/1^2- and shows an inverted one-electron reduction for 1/1^- at higher potentials. Electrochemical investigations of 1 are compared to the closely related [Fe(bdt)(CO)₂(PMe₃)₂] compound. A mechanistic suggestion for the hydrogen evolution reaction upon proton reduction from acid media is derived. The stability of 1 in both weak and strong acids is monitored by cyclic voltammetry.

Ligand effects on the electrochemical behavior of [Fe2(CO)5(L){μ-(SCH2)2(Ph)PO}] (L = PPh3, P(OEt)3) hydrogenase model complexes

In this paper we study the influence of substituting one CO ligand in [Fe₂(CO)₆{μ-(SCH₂)₂(Ph)PO}] (1) by better σ-donors (PPh₃(2) and P(OMe)₃(3)) in relation to the electrochemical behavior.