Group 10 Metal Benzene-1,2-dithiolate Derivatives in the Synthesis of Coordination Polymers Containing Potassium Countercations

Towards Substrate-Reagent Interaction of Lochmann-Schlosser Bases in THF: Bridging THF Hides Potential Reaction Site of a Chiral Superbase

The metalation of N,N-dimethylaminomethylferrocene in THF by the superbasic mixture of ⁿ BuLi/KO^t Bu proceeds readily at low temperatures to afford a bimetallic Li₂ K₂ aggregate containing ferrocenyl anions and tert-butoxide. Starting from an enantiomerically enriched ortho-lithiated aminomethylferrocene, an enantiomerically pure superbase can be prepared. The molecular compound exhibits superbasic behavior deprotonating N,N-dimethylbenzylamine in the α-position and is also capable of deprotonating toluene. Quantum chemical calculations provide insight into the role of the bridging THF molecule to the possible substrate-reagent interaction. In addition, a benzylpotassium alkoxide adduct gives a closer look into the corresponding reaction site of the Lochmann-Schlosser base that is reported herein.

Proton and Electron Transfer in the Formation of a Copper Dithiolene-Based Coordination Polymer

Metal bis(dithiolene) complexes are promising building blocks for electrically conductive coordination polymers. N-Heterocyclic dithiolene complexes allow their cross-linking via the coordination of N-donor atoms to additional transition metal ions. In this study, we present the formal copper(II) and copper(III) 6,7-quinoxalinedithiolene complexes [Cu(qdt)₂]^- and [Cu(qdt)₂]^2- (qdt^2-: 6,7-quinoxalinedithiolate), as well as the 2D coordination polymer Cu[Cu(Hqdt)(qdt)] (3). The dithiolene complexes were isolated as (Bu₄N)₂[Cu(qdt)₂] (1), Na[Cu(qdt)₂]·4H₂O (2a), [Na(acetone)₄][Cu(qdt)₂] (2b), and [Ni(MeOH)₆][Cu(qdt)₂]₂·2H₂O (2c). Their crystal structures reveal nearly planar complexes with a high tendency of π-stacking. For a better understanding of their coordination behavior, the electronic properties are investigated by UV-vis-NIR spectroscopy, cyclic voltammetry, and DFT simulations. The synthesis of the 2D coordination polymer 3 involves the reduction and protonation of the monoanionic copper(III) complex. A combination of powder X-ray diffraction, magnetic susceptibility measurements, as well as IR and EPR spectroscopy confirm that formal [Cu^II(Hqdt)(qdt)]^- units link trigonal planar copper(I) atoms to a dense 2D coordination polymer. The electrical conductivity of 3 at room temperature is 2 × 10^-7 S/cm. Temperature dependent conductivity measurements confirm the semiconducting behavior of 3 with an Arrhenius derived activation energy of 0.33 eV. The strong absorption of 3 in the visible and NIR regions of the spectrum is caused by the small optical band gap of E_g,opt = 0.65 eV, determined by diffuse reflectance spectroscopy. This study sheds light on the coordination chemistry of N-heterocyclic dithiolene complexes and may serve as a reference for the future design and synthesis of dithiolene-based coordination polymers with interesting electrical and magnetic properties.

Ni(ii) dithiolate anion composites with two-dimensional materials for electrochemical oxygen evolution reactions (OERs)

A redox active anionic nickel dithiolate complex was synthesized and its composites with GO, rGO and GN were prepared and used as electrocatalyts in the OER.

A Mixed-Valence Tetra-Nuclear Nickel Dithiolene Complex: Synthesis, Crystal Structure, and the Lability of Its Nickel Sulfur Bonds

In this study, by employing a common synthetic protocol, an unusual and unexpected tetra-nuclear nickel dithiolene complex was obtained. The synthesis of the [Ni4(ecpdt)6]2− dianion (ecpdt = (Z)-3-ethoxy-3-oxo-1-phenylprop-1-ene-1,2-bis-thiolate) with two K+ as counter ions was then intentionally reproduced. The formation of this specific complex is attributed to the distinct dithiolene precursor used and the combination with the then coordinated counter ion in the molecular solid-state structure, as determined by X-ray diffraction. K2[Ni4(ecpdt)6] was further characterized by ESI-MS, FT-IR, UV-Vis, and cyclic voltammetry. The tetra-nuclear complex was found to have an uncommon geometry arising from the combination of four nickel centers and six dithiolene ligands. In the center of the arrangement, suspiciously long Ni–S distances were found, suggesting that the tetrameric structure can be easily split into two identical dimeric fragments or two distinct groups of monomeric fragments, for instance, upon dissolving. A proposed variable magnetism in the solid-state and in solution due to the postulated dissociation was confirmed. The Ni–S bonds of the “inner” and “outer” nickel centers differed concurrently with their coordination geometries. This observation also correlates with the fact that the complex bears two anionic charges requiring the four nickel centers to be present in two distinct oxidation states (2 × +2 and 2 × +3), i.e., to be hetero-valent. The different coordination geometries observed, together with the magnetic investigation, allowed the square planar “outer” geometry to be assigned to d8 centers, i.e., Ni2+, while the Ni3+ centers (d7) were in a square pyramidal geometry with longer Ni–S distances due to the increased number of donor atoms and interactions.

Heterometallic coordination polymers based on homo- and heteroleptic Au(iii) dithiolene complexes

Two novel hetero- and homoleptic Au(iii) dithiolene complexes have been designed, synthesized, characterized and employed for the elaboration of heterometallic coordination networks.

Thiosemiquinoid Radical-Bridged CrIII2 Complexes with Strong Magnetic Exchange Coupling

Semiquinoid radical bridging ligands are capable of mediating exceptionally strong magnetic coupling between spin centers, a requirement for the design of high-temperature magnetic materials. We demonstrate the ability of sulfur donors to provide much stronger coupling relative to their oxygen congeners in a series of dinuclear complexes. Employing a series of chalcogen donor-based bis(bidentate) benzoquinoid bridging ligands, the series of complexes [(TPyA)₂Cr₂(^RL^4-)]²⁺ (^OLH₄ = 1,2,4,5-tetrahydroxybenzene, ^OSLH₄ = 1,2-dithio-4,5-dihydroxybenzene, ^SLH₄ = 1,2,4,5-tetrathiobenzene, TPyA = tris(2-pyridylmethyl)amine) was synthesized. Variable-temperature dc magnetic susceptibility data reveal the presence of weak antiferromagnetic superexchange coupling between Cr^III centers in these complexes, with exchange constants of J = -2.83(3) (^OL^4-), -2.28(5) (^OSL^4-), and -1.80(2) (^SL^4-) cm^-1. Guided by cyclic voltammetry and spectroelectrochemical measurements, chemical one-electron oxidation of these complexes gives the radical-bridged species [(TPyA)₂Cr₂(^RL^3-•)]³⁺. Variable-temperature dc susceptibility measurements in these complexes reveal the presence of strong antiferromagnetic metal-semiquinoid radical coupling, with exchange constants of J = -352(10) (^OL^3-•), - 401(8) (^OSL^3-•), and -487(8) (^SL^3-•) cm^-1. These results provide the first measurement of magnetic coupling between metal ions and a thiosemiquinoid radical, and they demonstrate the value of moving from O to S donors in radical-bridged metal ions in the design of magnetic molecules and materials.

Copper dithiolene [Cu(SC6H2Cl2S)2]− units connected to alkaline/copper complexes: from ionic assemblies to discrete molecular entities and coordination polymers

New coordination polymers or ion-pair complexes containing the [Cu(SC₆H₂Cl₂S)₂]⁻ entity and M⁺ (alkaline or Cu metals) has been obtained.