Xanthate Anions Research Articles

Removal of Ethyl Xanthate Anions from Contaminated Aqueous Solutions Using Hazardous Waste Slag Generated by Lignite Combustion

Removal of Ethyl Xanthate Anions from Contaminated Aqueous Solutions Using Hazardous Waste Slag Generated by Lignite Combustion

Visible-Light-Driven Deoxygenative Heteroarylation of Alcohols with Heteroaryl Sulfones.

The visible-light-promoted deoxygenative radical heteroarylation of alcohols was achieved in the absence of any external photosensitizers. The processes occur through the generation of xanthate salts from alcohols, followed by SET and fragmentation, delivering alkyl radicals to react with heteroaryl sulfones. This method is amenable for a wide range of alcohols with good functional group tolerance, providing a practical strategy for the alkylation of benzo-heteroaromatics. Mechanism studies indicate that direct visible-light excitation of xanthate anions and subsequent SET initiate the reactions.

Deuterium- and Electron-Shuttling Catalysis for Deoxygenative Deuteration of Alcohols.

A practical and precise method for visible-light-promoted deoxygenative deuteration of common aliphatic alcohols using D2O as the deuterium source is reported. Upon intermediacy of xanthate anions, a variety of primary, secondary, and tertiary alcohols can be facilely transformed into deuterioalkanes with excellent D-incorporation at predicted sites. The deoxygenation and deuteration sequence is catalyzed by in situ formed deuterated 2-mercaptopyridine, which plays dual roles as a deuterium atom transfer catalyst and an electron shuttle as well.

The low-carbon flotation separation of chalcopyrite from pyrite with a fire-new alkylamine-triazine-dithiol collector

Lowering lime consumption in froth flotation is one of the important aspects for carbon emission reduction. Herein, 6-butylamino-1,3,5-triazine-2(1H)-thione-4-thiol sodium (BN) was pioneeringly designed as a high-selective collector for copper sulfide flotation. The micro-flotation findings indicated that BN realized an effective separation of chalcopyrite from pyrite under pH ∼ 8.0. The further mechanism investigations through adsorption kinetics and thermodynamics, density functional theory (DFT) calculation, FTIR, UV and XPS suggested that BN self-assembled on chalcopyrite to generate the surface Cu-BN complexes where the CuS bonds were formed. Meanwhile, BN’s butyl group oriented outward for attaching bubbles to improve the floatability of chalcopyrite. In comparison to isobutyl xanthate anion (IBX−), BN anion (BN−) possesses the big conjugated configuration of amino-triazine dithiol group and strong electron delocalization ability. Moreover, BN− exhibited the stronger electron-accepting and weaker electron-donating ability than IBX−, which made BN− exhibit a strong affinity towards Cu(Ⅰ)/Cu(Ⅱ) atom(s) on chalcopyrite surface and weak interaction to Fe(Ⅱ)/Fe(Ⅲ) atom(s) on pyrite surface. Therefore, the pH for flotation separation of chalcopyrite against pyrite with BN was much lower than that with sodium isobutyl xanthate, reducing lime consumption and carbon emission.

Visible-Light-Driven Photocatalyst-Free Deoxygenative Radical Transformation of Alcohols to Oxime Ethers.

A visible-light-driven deoxygenative cross-coupling of alcohols with sulfonyl oxime ethers has been developed by using xanthate salts as alcohol-activating groups. Upon convenient generation and direct photoexcitation of xanthate anions, a broad range of alcohols including primary ones can efficiently undergo this transformation to afford diverse oxime ethers and derivatives. This one-pot protocol features mild conditions, broad substrate scope, and late-stage applicability, without the need for any external photocatalysts or electron donor-acceptor complex formation.

Deoxygenative coupling of alcohols with aromatic nitriles enabled by direct visible light excitation.

A general and practical protocol is presented for visible-light-driven deoxygenative coupling of alcohols with aromatic nitriles in the absence of external photocatalysts. Utilizing a hydroxyl activation strategy with carbon disulfide, this C(sp3)-C(sp2) constructing platform accommodates a broad scope of alcohols and aryl nitriles to deliver various alkyl-substituted arenes. Mechanism studies show that a single electron transfer event between a photoexcited aryl nitrile and a xanthate anion is key to the transformation.

Enhancement of xanthate adsorption on lead-modified and sulfurized smithsonite surface in the presence of ammonia

The contribution of ammonia to the sulfurization of Cu and Zn oxide minerals has been widely investigated, but the practical role of ammonia in the xanthate adsorption that directly determines the flotation of minerals has not been clearly confirmed. In this work, the promotion performance of NH3·H2O for xanthate adsorption onto the smithsonite surface was visually exhibited through adsorption density detection and the relating adsorption mechanism was revealed in terms of adsorption behavior and structure. Ultraviolet–visible spectroscopy and infrared spectroscopy tests showed that NH3·H2O treatment significantly increased the adsorption density of xanthate, with an increasing value of approximately 0.52 mg/m2 on the smithsonite surface at the initial xanthate concentration of 300 mg/L. With NH3·H2O treatment, the zeta potential of smithsonite particles increased, which was attributed to the chemisorption of Zn–NH3 complex cations on the mineral surface; such increased potential enhenced the proximity and adsorption probability for xanthate anions on the mineral surface through electrostatic attraction. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry analysis indicated that Pb–xanthate was the main xanthate product chemisorbed onto the Pb-modified and sulfurized smithsonite surface; NH3·H2O effectively increased the number of Pb sites on the surface and facilitated the transformation of the Pb(II)–S state to the Pb(II) xanthate state, resulting in an increase of Pb–xanthate content on smithsonite surface. Thus, NH3·H2O improved the hydrophobicity and increased the flotation recovery of smithsonite by approximately 10% in the Pb ion-modified sulfurization–xanthate system.

Direct Photoexcitation of Xanthate Anions for Deoxygenative Alkenylation of Alcohols.

In this report, we identify xanthate salts as a unique class of visible-light-excitable alkyl radical precursors that act simultaneously as strong photoreductants and alkyl radical sources. Upon direct photoexcitation of xanthate anions, efficient deoxygenative alkenylation and alkylation of a wide range of primary, secondary, and tertiary alcohols have been achieved via a one-pot protocol, avoiding any photocatalysts. This method exhibits a broad substrate scope and good functional group tolerance, enabling late-stage functionalization of complex molecules.

Visible-light-driven photocatalyst-free deoxygenative alkylation of imines with alcohols

In this report, we developed a photocatalyst-free visible-light-promoted deoxygenative alkylation of imines with alcohols assisted by carbon disulfide and tricyclohexylphosphine. The key to success of this method is the activation of alcohols upon the formation and direct photoexcitation of xanthate anions. This one-pot protocol enables the selective C-O bond homolysis of diverse primary, secondary and tertiary alcohols to react with a variety of N-sulfonyl and N-aryl imines, providing a general and efficient platform for α-branched amine synthesis from alcohols.

Synthesis of Spirooxindoles Bearing 1,3‐Oxathiolane‐2‐thione Moiety From Isatin‐Derived Propargylic Alcohols

Spirooxindoles bearing 1,3‐oxathiolane‐2‐thione moiety were synthesized from isatin‐derived propargylic alcohols and carbon disulfide in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU). The spirooxindoles were formed stereoselectively via attack of the alkoxide of propargylic alcohol to carbon disulfide to form xanthate anion and a following 5‐exo‐dig cyclization process.

Anionic sigmatropic-electrocyclic-Chugaev cascades: accessing 12-aryl-5-(methylthiocarbonylthio)tetracenes and a related anthra[2,3-b]thiophene.

1,4-Diols resulting from the double addition of ArCCLi (Ar = Ph, substituted phenyl, 2-thienyl) to ortho-C6H4(CHO)2 undergo cascades to tetracenes on simple admixture of LiHDMS, CS2 and MeI. Acene formation proceeds by [3,3]-sigmatropic rearrangement of xanthate anions followed by 6π electrocyclisations. The reactions are terminated by E2 or anionic Chugaev-type eliminations. Structural packing motifs and electronic properties are reported for the tetracenes.

Crystal structure of bis-(3-bromo-pyridine-κN)bis-(O-ethyl di-thio-carbonato-κ(2) S,S')nickel(II).

In the title mol­ecular complex, [Ni(C3H5OS2)2(C5H4BrN)2], the Ni2+ cation is located on a centre of inversion and has a distorted octa­hedral N2S4 environment defined by two chelating xanthate ligands and two monodentate pyridine ligands. The C—S bond lengths of the thio­carboxyl­ate group are indicative of a delocalized bond and the O—Csp 2 bond is considerably shorter than the O—Csp 3 bond, consistent with a significant contribution of one resonance form of the xanthate anion that features a formal C=O+ unit and a negative charge on each of the S atoms. The packing of the mol­ecules is stabilized by C—H⋯S and C—H⋯π inter­actions. In addition, π–π inter­actions between the pyridine rings [centroid-to-centroid distance = 3.797 (3) Å] are also present. In the crystal structure, mol­ecules are arranged in rows along [100], forming layers parallel to (010) and (001).

Cis-Bis(O-methyldithiocarbonato-κ2S,S′)bis(triphenylphosphane-κP)ruthenium(II)

In the title compound, [Ru(CH3OCS2)2(C18H15P)2], the RuII atom is in a distorted octa­hedral coordination by two xanthate anions (CH3OCS2) and two tri­phenyl­phosphane (PPh3) ligands. Both bidentate xanthate ligands coordinate the RuII atom with two slightly different Ru—S bond lengths but with virtually equal bite angles [71.57 (4) and 71.58 (3)°]. The packing of the complexes is assured by C—H⋯O and C—H⋯π inter­actions.

A distorted geometry of methyl xanthate anion in S 3 state—Resonance Raman and ab initio studies

The A-band resonance Raman spectra were obtained for methyl xanthate anion in methanol solution. Density functional calculations were done to help elucidate its ultraviolet electronic transitions and to assign the resonance Raman spectra. The results indicate that the Franck–Condon region photodissociation dynamics have multidimensional character with motion predominantly along the symmetric CS 2 stretch, accompanied by the COC stretch, the CH 3 wag, the COC scissor, the CS 2 scissor, and overtone of the OCS 2 out of plane deformation. RCIS/6-31G ∗ calculations were done to predict the distorted geometry structure and the saddle point of methyl xanthate anion in S 3 excited state.

New Aspects of the Electroadsorption of Ethyl Xanthate on Copper Electrodes

The interaction of the ethyl xanthate (EX) anion with a copper electrode in a borate buffer solution, pH 9.2, has been investigated by cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), electrochemical impedance spectroscopy (EIS), and measurements of contact angle (CA) under controlled potential. The results obtained allow establishing that, in the potential range from -0.80 and -0.60 V, two parallel reactions were characterized. These reactions were the ethyl xanthate electroadsorption and the hydrogen evolution reaction (HER). This last reaction has not been described by previous authors. Besides, the EIS measurements show that the mechanism of the HER on copper electrodes is not affected by the presence of a ethyl xanthate species. The EQCM study shows that in the electrodesorption process the departure of each ethyl xanthate species from the copper electrode is accompanied with the simultaneous entry of four to five water molecules. This fact is in accordance with the number of copper atoms involved in the adsorption of one ethyl xanthate species.

Xanthate sulfur as a hydrogen bond acceptor: the free xanthate anion and ligand sulfur in nickel tris ethylxanthate

Xanthates, like thiolates, form a variety of complexes with metals in which coordinating sulfur can serve as a hydrogen bond acceptor. Nickel tris xanthate complexes [Ni(xan) 3] −, (xan = o-ethylxanthate, N-(carbamoylmethyl)ethylxanthate) have been synthesized and compared by a combination of X-ray crystallographic and spectroscopic measurements. Recent results from our studies of N–H⋯S hydrogen bonding interactions in metal–xanthate complexes shows N–S distances to be longer than those in related thiolate complexes, indicative of weaker hydrogen bonds for the xanthates. The complex (Et 4N)[N-(carbamoylmethyl)ethylxanthate)] adopts an extended conformation in both the solid state and solution and lacks either intraligand or intermolecular N–H⋯S hydrogen bonds. The complex (CTA)[Ni(exa) 3] exhibits N–H⋯S hydrogen bonds between the amide group of the counterion and the ligand sulfur. The amide–sulfur N–H⋯S distance is 3.567 Å.

Investigations on preparation, crystal structure and thermal stability of bis (O‐ethylcarbonodithiolato‐S, S′) (1,10‐phenanthroline‐N1, N10) cobalt(II) complex: [Co(Et‐XA)2· phen] ± H2O (XA = xanthate)

Abstract[Co(Et‐XA)2· phen] ± H2O was prepared by adding 1,10‐phenanthroline to the EtOH solution of bis(O‐ethylcarbonodithiolato) cobalt(II) [Co(Et‐XA)2]. The single crystal structure has been determined by X‐ray diffraction analysis. The compound is orthorhombic with space group Pna21 and unit‐cell parameters a = 1.0290(2) nm, b = 1.4550(3) nm and c = 1.4860(3) nm. The geometry of each Co atom which coordinates with four S atoms from two xanthate anions and two N atoms from phenanthroline ligand, is a distorted octahedron. The brown crystals were examined by elemental analysis, FT‐IR, UV spectra and thermogravimetric‐differential thermal analysis (TG‐DTA). Thermal decomposition of the compound takes place in several steps. In the first step, the compound releases 1, 10‐phenanthroline ligand, then loses the H2O molecules. In the second step, the complex decomposes to CoS3. The final product of thermal decomposition is CoS. Elemental analysis, IR and UV spectra are in agreement with the proposed structure.

Characterization and Molecular Structure of Bis(Isopropyl Xanthate) Bis(1,10-Phenanthroline) Nickel(II): [Ni(phen)2(CH3)2CHOCSS](CH3)2CHOCSS

The crystal and molecular structure of the title compound, [Ni(phen)2(CH3)2CHOCSS](CH3)2CHOCSS has been determined by X-ray diffraction. The brown crystal is triclinic of space group Pi, with parameters a = 11.790(2), b = 12.410(3), c = 12.680(3) Å, α = 92.49(3), β = 96.54(3), γ = 117.43(3)° and Z = 2. The compound contains a six-coordinate cation and an isopropyl xanthate anion (CH3)2CHOCSS−, the central Ni atom is chelated by four nitrogen atoms of two phenanthroline ligands and two sulfur atoms of an isopropyl xanthate ligand. The TG data indicate that it decomposed completely at 734°C.

Crystal structure of anhydrous potassium O-n-propyldithiocarbonate. Theoretical calculations of O-alkyl dithiocarbonates

Abstract The xanthate anion in the structure of K[S2COnPr] displays the expected features, i.e. planar S2CO chromophore and variation in C—S and C—O distances. The K cation exists in a distorted cubic geometry defined by an O2S6 donor set. Cubes are face-shared so as to form a layer structure with cohesion between layers afforded by hydrophobic interactions. A series of theoretical gas-phase structures have been calculated for isolated S2COR anions. These show that there is a remarkable consistency in geometric parameters across the series. This observation indicates that the nature of the R substituent does not influence greatly the electronic structure of the central S2CO chromophore.

Synthesis and Thermal Studies on Some Bimetallic Mixed-Ligand Complexes Containing a Bis-Bidentate Onno Schiff Base and Alkylxanthate Ligands

New bimetallic mixed-ligand complexes of the general formula [M2(sal-bz)(Rxan)2(DMF)n], where M = Ni(II), Co(II) or Cu(II); sal-bz= dianion of a tetradentate Schiff base derived from salicylaldehyde and benzidine; xan = xanthate anion; R = methyl, ethyl or butyl; n - 2 or 4, have been prepared and characterized by elemental analyses, molar conductance, IR and electronic spectral data. The thermal decomposition of some of these complexes has been studied. The TG curves show that the decomposition takes place in two well-defined steps. The first step involves the elimination of DMF molecules and the decomposition of the alkyl xanthate via a radical mechanism. This was accompanied by the formation of an intermediate product which decomposed in a second step to the metal sulphide as the end product. Activation energies and other kinetic parameters were computed.