The Chemistry of the Dithioacid and 1,1-Dithiolate Complexes

Mining flotation reagents: Quantitative and robust analysis of metal-xanthate complexes in water

Xanthates, common mining flotation reagents, strongly bind thiophilic metals such as copper (Cu), lead (Pb), cadmium (Cd), and zinc (Zn) and consequentially change their bioavailability and mobility upon their discharge into the environment. However, accurate quantification of the metal-xanthate complexes has remained elusive. This study develops a novel and robust method that realizes the accurate quantification of the metal-xanthate complexes resulted from single and multiple reactions of three typical xanthates (ethyl, isopropyl, and butyl xanthates) and four thiophilic metals (Cu, Pb, Cd, and Zn) in water samples. This method uses sulfur (S2-) dissociation, followed by tandem solid phase extraction of C18 + PWAX and subsequent LC-MS/MS analysis. It has a wide linearity range (1-1000 μg/L, R2 ≥ 0.995), low method detection limits (0.002-0.036 μg/L), and good recoveries (70.6-107.0 %) at 0.01-10 mg/L of xanthates. Applications of this method showed ubiquitous occurrence of the metal-xanthate complexes as the primary species in flotation wastewaters, which the concentrations were 4.6-28.9-fold higher than those previously determined. It is the first quantitative method established for the analysis of metal-xanthate complexes in water samples, which is of great importance to comprehensively understand the fate and risks of xanthates in the environment.

Coordination Chemistry of the Parent Dithiocarbamate H2NCS2-: Organometallic Chemistry and Tris-Chelates of Group 9 Metals

Two tris-chelate complexes of cobalt and rhodium and two complexes of Ru(II) of dithiocarbamate, [S₂CNH₂]^-, were synthesized. The complexes were spectroscopically characterized by IR, NMR, UV-vis, and MS and structurally characterized by X-ray diffraction. The structural features of the rhodium complex were compared to those of other tris-chelate Rh(III) dithiocarbamate complexes and are characterized by a change in the ground-state geometry in comparison to expected octahedral tris-chelate complexes. This was confirmed both experimentally by X-ray diffraction and theoretically using DFT calculations. The inversion barriers of Rh(Bz₂dtc)₃, Ir(Bz₂dtc)₃, and Rh(Et₂dtc)₃ were determined using VT-NMR in DMSO. These barriers were found to be surprisingly low for heavy group 9 elements of d⁶ tris-chelate complexes: values of 16.7, 17.1, and 16.4 kcal/mol were calculated, respectively. By comparing structural features, we are able to determine that the activation barrier for the inversion of stereochemistry of Rh(H₂dtc)₃ must have a similarly low value. A modified version of the Bailar twist involving an intermediate with C_3h geometry was proposed as the mechanism of inversion.

The Coordination Chemistry of Imidomethanedithiolate Di-anions: A Structural Comparison with Their Dithiocarbamate Analogs

A review of the coordination chemistry along with the structural features of heavy element complexes of dithiocarbimate di-anions in the form of [(R)C=NCS2]2− for R = CN, alkyl, and aryl are described. This class of compound is far less studied compared with the well-explored dithiocarbamate mono-anions formulated as [R(R’)NCS2]− for R/R’ = H, alkyl, and aryl. The coordination chemistry of dithiocarbimate di-anions is dominated by a S,S-chelating mode; rare examples of alternative modes of coordination are evident. When comparisons are available, the structural motifs adopted by metal dithiocarbimate complexes match those found for their dithiocarbamate analogs, with only small, non-systematic variations in the M–S bond lengths.

Metallostar Assemblies Based on Dithiocarbamates for Use as MRI Contrast Agents

Two different octadentate gadolinium chelates based on DO3A and DOTAGA chelates (hydration number q = 1) have been used to prepare a series of bi-, tri-, and tetrametallic d-f mixed-metal complexes. The piperazine-based dithiocarbamate linker ensures that rotation of the gadolinium chelates is restricted, leading to enhanced relaxivity (r₁) values, which increase with the overall mass and number of gadolinium units. The r₁ value (at 10 MHz, 25 °C) per gadolinium unit rises from 5.0 mM^-1 s^-1 for the Gd-DO3A-NH₂ monogadolinium chelate to 9.2 mM^-1 s^-1 in a trigadolinium complex with a ruthenium(III) core. Using a 1.5 T clinical scanner operating at 63.87 MHz (25 °C), an 86% increase in the relaxivity per gadolinium unit is observed for this multimetallic compound compared to clinically approved Dotarem. The gadolinium complexes based on the DOTAGA chelate also performed well at 63.87 MHz, with a relaxivity value of 9.5 mM^-1 s^-1 per gadolinium unit being observed for the trigadolinium d-f mixed-metal complex with a ruthenium(III) core. The versatility of dithiocarbamate coordination chemistry thus provides access to a wide range of d-f hybrids with potential for use as high-performance MRI contrast agents.

Chemistry and Some Biological Potential of Bismuth and Antimony Dithiocarbamate Complexes

Interest in the synthesis of Bi(III) and Sb(III) dithiocarbamate complexes is on the rise, and this has been attributed to their wide structural diversity and their interesting application as biological agents and in solid state/materials chemistry. The readily available binding sites of the two sulphur atoms within the dithiocarbamate moiety in the complexes confers a wide variety of geometry and interactions that often leads to supramolecular assemblies. Although none of the bismuth or antimony metals are known to play any natural biological function, their dithiocarbamate complexes, however, have proven very useful as antibacterial, antileishmanial, anticancer, and antifungal agents. The dithiocarbamate ligands modulate the associated toxicity of the metals, especially antimony, since bismuth is known to be benign, allowing the metal ion to get to the targeted sites; hence, making it less available for side and other damaging reactions. This review presents a concise chemistry and some known biological potentials of their trivalent dithiocarbamate complexes.

The crystal structure of bis[μ2-(N,N-diethylcarbamodithioato-κS:κS,κS′)] bis[1′-(diphenylphosphino-κP)-1-cyanoferrocene]disilver(I), C56H56Ag2Fe2N4P2S4

C56H56Ag2Fe2N4P2S4, triclinic, P1̄ (no. 2), a = 9.5058(2) Å, b = 10.8362(2) Å, c = 14.3325(3) Å, α = 72.400(1)°, β = 75.241(1)°, γ = 77.132(1)°, V = 1343.71(5) Å3, Z = 1, R gt(F) = 0.0191, wR ref(F 2) = 0.0443, T = 150(2) K.

Mono- and bimetallic manganese-carbonyl complexes and clusters bearing imidazol(in)ium-2-dithiocarboxylate ligands

Five complexes with the generic formula fac-[MnBr(CO)₃(S₂C·NHC)] were obtained by reacting [MnBr(CO)₅] with a set of representative imidazol(in)ium-2-dithiocarboxylate zwitterions. These ligands are the adducts of N-heterocyclic carbenes (NHCs) and carbon disulfide. The mononuclear Mn(i) derivatives were coupled with Na[Mn(CO)₅] to afford bimetallic [Mn₂(CO)₆(S₂C·NHC)] clusters. Yet, the most convenient strategy to access these dinuclear Mn(0) products implied a direct carbonyl substitution from the [Mn₂(CO)₁₀] dimer. The molecular structures of three monometallic and four bimetallic compounds were elucidated by single crystal X-ray diffraction analysis. In the monometallic complexes, the NHC·CS₂ ligands exhibited a bidentate κ²-S,S' coordination mode with an S-C-S bite angle of about 116°. In the dinuclear clusters, the CS₂^- unit acted as a chelate toward one manganese center and as a pseudoallylic ligand toward the other one. The S-C-S bite angle was reduced to ca. 104°. Thus, the zwitterions displayed a remarkable flexibility, which also permitted a staggered arrangement of the carbonyl groups in the bimetallic systems. Examination of the [small nu, Greek, macron]_CO absorption bands on IR spectroscopy helped identify the presence of fac-Mn(CO)₃ or Mn₂(CO)₆ motifs, while the ¹³C NMR chemical shift of the CS₂^- moiety was a reliable indicator for monitoring its hapticity. Whereas the dinuclear clusters were air- and moisture-stable crystalline solids, mononuclear halido derivatives displayed only a limited stability under aerobic conditions. Both types of compounds underwent rather unselective, extensive fragmentations in the gas phase, in sharp contrast with the analogous rhenium derivatives that led to clean sequential decarbonylation processes upon collision-induced dissociation.

Supramolecular association via Sb...S and C-H...S interactions in dimeric tris(N,N-dimethyldithiocarbamato-S,S')antimony(III): an approach to overcome the concept of steric bulk on such interactions

Tris(N,N-dimethyldithiocarbamato-S,S')antimony(III) has been isolated as a dimer in acetonitrile. Single-crystal X-ray analysis shows that the molecule possesses both Sb···S and C-H···S interactions, which results in a supramolecular association in the absence of hydrogen-bonding functionality on the R group. The co-existence in the title compound of such interactions is a unique character of known dimeric antimony(III) alkyl and/or aryl dithiocarbamate complexes. The literature reveals that the species where the alkyl and/or aryl dithiocarbamates carry the following groups: R = methyl (chloroform solvated), ethyl, n-propyl, pyrrolidine, morpholine, piperidine, azepane, benzyl, methylphenyl, are not capable of forming significant hydrogen-bonding interactions. However, either Sb···S or C-H···S intermolecular interactions dominate between two centrosymmetrically related molecules leading to a supramolecular aggregation. In the species where the R group carries hydrogen-bonding functionality, i.e. 2-hydroxylethyl, the C-H···S interactions are subverted by O-H···O hydrogen bonding. In addition, the title compound does not have steric hindrance or any hydrogen-bonding group but is stabilized with the co-existence of Sb···S and C-H···S interactions. Analysis of the secondary interactions of a series of analogues previously reported reveals that steric bulk is unnecessary for the mitigation of Sb···S interactions and for the establishment of C-H···S secondary bonding.

Poly[di-μ-aqua-[μ6-N-(4-bromophenylsulfonyl)dithiocarbimato]dipotassium] and poly[di-μ-aqua-[μ4-N-(4-iodophenylsulfonyl)dithiocarbimato]dipotassium]

The rigid organic linkersN-(4-bromophenylsulfonyl)dithiocarbimate(2−) andN-(4-iodophenylsulfonyl)dithiocarbimate(2−) crystallize with two potassium cations and two water molecules in their asymmetric units, forming the title coordination polymers, [K2(C7H4BrNO2S3)(H2O)2]nand [K2(C7H4INO2S3)(H2O)2]n. The anions and the water molecules link the potassium cations into broad two-dimensional networks, which are further linked by K...halide interactions.