Thio Complexes Research Articles

Synthesis of isotopomeric binuclear thio complexes of molybdenum and tungsten and the study of their vibrational spectra

Alkylammonium salts, W 2 34S 4X 4 2− (X = Cl, Br), M 2 34S 4Br 8 2− (M = Mo, W) and Mo 2 34S 6O 2 2−, have been obtained from 34S 8. IR and Raman spectra of these compounds have been studied and the normal vibrations calculated. A number of vibrations involving sulphur atoms [for example v(MS), v(SS)] are characteristic, which allows vibrational spectroscopy to be used to study the changes occurring in the metal-sulphur containing fragments. The interaction of W 2(μ 2-S)(μ 2-S 2)Br 8 2− with 34S 8 was shown to produce W 2(μ 2-S 2) 2Br 8 2−. The reaction of Mo 2(μ 2- 34S 2) 2Cl 4C 4/2 with S x 2− results in the replacement of 34S by 32S to produce the Mo 2(μ 2-S 2) 2(S 2) 4 2− complex.

Properties of homogeneous and heterogeneous rhenium catalysts in the hydrogenation of nitro compounds

The behaviour of soluble rhenium(V) oxohalide complexes with coordinatively bound thiourea, triphenylphosphine and their derivatives has been studied in the hydrogenation of C 6-C 10 olefins, nitrobenzene and p-nitrotoluene. Under homogeneous conditions rhenium complexes containing a Re-S bond were found to catalyze the reduction of the nitro group selectively, whereas those involving a Re-P bond catalyze the reduction of olefins. Activated rhenium thiourea complexes have been isolated in the solid state from the reaction medium. Their analogs, thio complexes, displaying similar physicochemical properties and catalytic activity, and which work without an induction period under atmospheric pressure have been synthesized. In the hydrogenation of 15 substituted nitrobenzenes, soluble rhenium complexes and solid rhenium heptasulfide were found to possess similar catalytic activities due to having the same catalytic center. The hydrogenation of the nitro group is accelerated by electron-acceptor functional groups and is inhibited by electron-donor ones.

Fluid inclusion studies on the gold deposits of the upper Anzasca Valley, northwestern Alps, Italy

The gold deposits of the upper Anzasca Valley are part of the Monte Rosa gold district, northwestern Alps, Italy. The mineralization occurs within polymetamorphic Paleozoic metasedimentary and metagranitic rocks of the Pennidic Monte Rosa unit. The orebodies consist of more or less concordant veins where they are hosted by metasedimentary rocks, whereas in the metagranites they occupy fractures and shear zones discordant with the foliation. Field evidence suggests, however, a common late Alpine age for the emplacement of both types of orebodies.The mineralogy of the orebodies is dominated by quartz. Gold is invariably associated with sulfides (pyrite, arsenopyrite, galena, sphalerite, chalcopyrite, and sulfosalts).The characteristics of fluid inclusions in quartz from gold-bearing veins are remarkably consistent: the inclusions are moderately saline brines containing, at room temperature, about 20 to 60 percent vol of a low-density, rather pure CO 2 phase; they were probably homogeneous at the time of trapping. Small amounts of CH 4 occur in some inclusions. Total homogenization occurs either in the liquid or in the gas phase, or by near-critical phenomena, at temperatures mostly on the order of 300 degrees to 350 degrees C. By combining these temperatures with geologic pressure estimates and with temperatures inferred from arsenopyrite compositions, trapping conditions of about 400 degrees to 450 degrees C at pressures of 1 to 1.5 kbars are derived. A less common, presumably later, type of CO 2 -poor inclusion is interpreted as a late influx of cooler and less saline fluids.Quartz from barren veins also contains CO 2 -bearing inclusions; however, these show higher T (sub m clathrate ) , lower T (sub h (sub CO 2 ) ) , and lower total homogenization temperatures than mineralized veins.Results of reconnaissance studies on fluid inclusions from other gold deposits (Val Sesia, Val Toppa) in the Monte Rosa district are somewhat different from those of the upper Anzasca Valley: the CO 2 phase is of higher density, and total homogenization temperatures are lower.Combined with field evidence and available Pb and O isotope data, the fluid inclusion characteristics are consistent with a model of ore genesis in which the gold deposits of the upper Anzasca Valley were formed in the late stages of the Alpine orogeny by presumably metamorphic fluids, probably produced by devolatilization of deep unexposed portions of Monte Rosa crustal rocks. The strict association of gold with sulfides suggests that gold possibly was transported as thio complexes. Possible precipitation mechanisms include cooling, dilution, minor wall-rock reaction, and decrease of sulfur activity in the fluid.Similar processes probably were active in the formation of other neighboring gold deposits, but there is evidence that gold deposition, on a regional scale, was related to at least two distinct hydrothermal systems separate in space and also in time.

Electrooxidative formation and characteristics of Cr(III)-thio complexes at mercury electrodes

Oxidation of Cr 2+ at mercury electrodes in the presence of S 2O 2− 3, thiosemicarbazide, 2,5-dimercapto-1, 3,4-thiadiazole, N-methylthiourea, thiourea and thioacetamide lead to Cr(III) complexes which feature a chromium(III)-sulphur bond. The equilibrium constants of these complexes are equal to 0.21, 0.14, 0.036, 0.0076, 0.0013 and 0.00015 M −1 for S 2O 2− 3, TSC, DMTDA, NMTU, TU and TAA, respectively. The Cr(III)TU complex synthesized electrochemically aquates spontaneously, and the mechanism of this reaction is the same as that characteristic of other Cr(III)X (3- i)+ complexes. This complex is not adsorbed on the electrode surface.

Elevation of copper nuclear quadrupole coupling in thio complexes by completion of the coordination sphere

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElevation of copper nuclear quadrupole coupling in thio complexes by completion of the coordination sphereDeborah L. Liczwek, R. Linn Belford, John R. Pilbrow, and James S. HydeCite this: J. Phys. Chem. 1983, 87, 14, 2509–2512Publication Date (Print):July 1, 1983Publication History Published online1 May 2002Published inissue 1 July 1983https://doi.org/10.1021/j100237a014RIGHTS & PERMISSIONSArticle Views75Altmetric-Citations23LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (490 KB) Get e-Alerts

Isolation of thiomolybdate compounds from the molybdenum-iron protein of clostridial nitrogenase.

Acid/base treatment of the molybdenum-iron protein of the nitrogenase from Clostridium pasteurianum 25 yields low-molecular-weight compounds of molybdenum, which can be separated from the protein by gel chromatography. Elementary analysis and spectral properties relate these compounds to thiomolybdate anions. It is proposed that in its native state nitrogenase contains a thio complex of molybdenum coupled to iron-sulfur clusters.

Copper and inflammation

Bonta, Sorenson and others have shown that Cu(II) derivatives are effective anti-inflammatory agents. Some chemical and pharmacological properties of Cu(I) and metallic Cu are discussed. Thio complexes of Cu(I) were prepared and shown to be useful anti-inflammatory agents in rats. Hypotheses are stated concerning the possible therapeutic value of copper in its various oxidation states.

Volatile and precious metal zoning in the Broadlands geothermal field, New Zealand

Au, Ag, As, Sb, Tl, Se, Te, Co, and Bi have been determined by neutron activation analysis in samples from two deep diamond drill holes, hot-spring sinters, and precipitates from discharge waters from the Broadlands, New Zealand, geothermal field. Ore-grade amounts of Au and Ag are being deposited from the dilute hydrothermal waters at the surface, whereas erratically distributed sulfides (mainly pyrite with minor galena, sphalerite, and chalcopyrite) make up to 10 percent of the hydrothermally altered volcanic rocks at depth. Bore temperatures in BR 16 (the main hole studied) range from 280 degrees C at 1,400 meters depth to 60 degrees C at 80 meters depth. The data confirm the existence of a crude metalliferous zoning with As, Sb, Au, and Tl enriched in near-surface regions while Ag, Se, Te, Bi, Pb, Zn, Cu, and Co are concentrated mainly at depth.Deposition of Tl is occurring solely in response to decreasing solution temperatures while the other elements are being precipitated through the combined effects of decreasing temperatures and boiling within permeable zones. It is concluded that they are being transported as thio complexes which become unstable due to loss of H 2 S, CO 2 , and/or NH 3 during boiling. Trace elements may have been coprecipitated with major element sulfides through adsorption and incorporation into sulfide lattices. Solution/wall-rock interactions and oxidation processes appear to be unimportant depositional mechanisms at Broadlands, while the possibility that dilution has caused deposition cannot be properly evaluated.Tl enrichment halos are predicted around many base metal deposits. These could be more pervasive and uniform than those formed by other metals because Tl would have been deposited mainly in response to decreases in temperature away from hydrothermal vents, etc. Since Tl substitutes for K in potash-rich silicates, it may also survive metamorphic effects better than other volatile metals which might also form primary dispersion halos around ore deposits.

Thio complexes of gold and the transport of gold in hydrothermal ore solutions

The solubility of gold in aqueous sulphide solutions has been determined from pH 20°C ≈ 4 to pH 20°C ≈ 9.5 in the presence of a pyrite-pyrrhotite redox buffer at temperatures from 160 to 300°C and 1000 bar pressure. Maximum solubilities were obtained in the neutral region of pH as, for example, with m NaHS = 0.15 m, pH 20°C = 5.96, T = 309° C, P = 1000 bar where a gold solubility of 225 mg/kg was obtained. It was concluded that three thio gold complexes contributed to the solubility. The complex Au 2(HS) 2S 2− predominated in alkaline solution, the Au(HS) 2 − complex occurred in the neutral pH region, and in the acid pH region, it was concluded with less certainty that the Au(HS)° complex was present. Formation constants calculated forAu 2(HS) 2S 2− and Au (HS) 2 − emphasize their high stability. In the temperature range from 175 to 250°C, values of pβ for Au 2(HS) 2S 2− vary from −53.0 to 47.9 (±1.6) and from −23.1 to −19.5 ( ± 1.5) for Au(HS) 2 −. Equilibrium constante for the dissolution reactions, Au° + H 2S + HS − ⇋ Au(HS) 2 − + 1 2 H 2 and 2 Au° + H 2 S + 2 H8 − ⇋ Au( HS) 2 − + H 2 vary from pK m = +2.4 to +2.55 (±0.10) for Au 2(HS) 2S 2− and from pK n = + 1.29 to + 1.19 (±0.10) for Au(HS) 2 − over the temperature range 175 to 250°C. Enthalpies of these dissolution reactions were calculated to be ΔH m ° = −5.2 ±2.0 kcal/mol and ΔH n ° = +1.7 ±2.0 kcal/ mol respectively. It was concluded that gold is probably transported in hydrothermal ore solutions as both thio and chloro complexes and may be deposited in response to changes in temperature, pressure, pH, oxidation potential of the system and total sulphur concentration.

Magnetically anomalous thio complexes of iron(III) and nickel(II)

Thioxanthate complexes closely resemble the xanthates and the dithiocarbamates. Like the corresponding xanthates and dithiocarbamates, thioxanthates of iron(111), nickel(11), and copper(11) are black and those of cobalt(111) are dark green. In sufficiently dilute solutions, iron(111) and nickel(11) thioxanthates are more red than xanthates and dithiocarbamates which are brownish red. The pressure and temperature dependences of the magnetism show that the ferric thioxanthates exhibit a high-spin + low-spin electronic equilibrium, like the ferric dithiocarbamates and xanthates, though the low spin form predominates for the xanthates and thioxanthates. Pyridine forms green paramagnetic adducts in the solid with the nickel(11) complexes which lose pyridine if left in the open, while in solution a concentration dependent equilibrium is set up between the planar thioxanthates and its bis-pyridine adduct. In general the complexes are rather unstable at room temperature, but some kept fairly well if stored frozen in sealed tubes. The iron(111) thioxanthates Fe(S2C-S-R)3 are at least as stable as the corresponding xanthates. Analogously to the case of the xanthates, the stability of the thioxanthates decreases and the ability of the ligand to reduce the central metal atom increases with increasing chain length when R is an alkyl group. Some long-chain ligands are capable of reducing the central iron atom to form an iron(11) complex. Complexes with branched alkyl chains are more stable than the straight-chain analogues.