Chemical Dissolution of Chalcopyrite Concentrate in Choline Chloride Ethylene Glycol Deep Eutectic Solvent

Currently, the high demand for copper is in direct contrast with the decrease in the mineral grade and, more significantly, the concerns regarding the environmental impact that arise as a result of processing such low-grade materials. Consequently, new mineral processing concepts are needed. This work explores the chemical dissolution of chalcopyrite concentrate at ambient pressure and moderate temperatures in a deep eutectic solvent. Copper and iron are dissolved without changing their oxidation state, without solvent pH change, and stabilized as a chloride complex with no evidence of passivation. Chemical equilibria of the metallic chloride complexes limit the dissolution, and the step that is rate-controlling of the kinetics is the interdiffusion of species in the solvent. The chemical mechanism may involve initial chloride adsorption at positive sites of the solid surface, pointing out the importance of surfaces states on chalcopyrite particles. A model based on a shrinking particle coupled with pseudo-second-order increase in the liquid concentration of copper describes the dissolution kinetics and demonstrates the importance of the liquid to solid ratio. Iron and copper can be recovered separately from the solvent, which highlights that this concept is an interesting alternative to both redox-hydrometallurgy and pyrometallurgy to obtain copper by the processing of chalcopyrite concentrate.

Synthesis and photophysical properties of rare earth complexes bearing silanediamido ligands Me2Si(NAryl)22– (Aryl = Dipp, Mes)

A series of rare earth (RE) chloride complexes bearing silanediamido ligands (LAryl)2– = Me2Si(NAryl)22– with bulky substituents, Aryl = mesityl (Mes), and 2,6-diisopropylphenyl (Dipp) was synthesized by salt metathesis reactions....

New Evidence of the Brizziite, Sodium Antimonate from the Central Paratethys Sea Strata in Poland

Brizziite, a rare sodium antimonate (NaSb5+O3), and fluorcalcioroméite ((Ca,Na)2Sb5+2O6F), have been identified in two boreholes (Pasternik and Włosienica) which are situated 50 km apart. Both wells are located west of Krakow, Poland, and were drilled in the Miocene strata of the Paratethys Sea (a remnant of the Tethys Ocean). The Sb minerals are scattered in a solidified light blue silica gel within marls and layered clays. They occur most often as anhedral grains up to 20 μm in size. The presence of these phases was confirmed by Raman spectroscopy (RS) and X-ray diffraction (XRD). The brizziite from this study represents a secondary mineral after the alteration of roméite within a supergene zone, or crystallization from Sb-rich solutions derived by the leaching of the weathered primary roméite. Hence, the calcium and fluorine admixtures in their composition, determined by EPMA, indicate intergrowths of brizziite and roméite on the micro- to crypto-scale. The presence of the antimony in the study area is related to rejuvenated Old-Paleozoic polymetallic ore-mineralization occurring in the basement of the Krakow-Silesia Monocline. The phenomenon of the repeatability of brizziite in Pasternik and Włosienica, distant by several tens of kilometers, can be explained by the following three steps: (i) the penetration of the chloride ions from the drying up seawaters of the Paratethys Sea into the Miocene groundwater system, (ii) the mobilization of Sb5+ in the form of chloride complexes, and, finally, (iii) the transportation of the Sb-bearing solutions within the marly and clay sediments.

3D Series Metal Complexes Containing Schiff Base Ligand with 2,2'-Bipyridine: Synthesis, Characterization and Assessment of Antifungal Activity

The rapid increase in the number of multidrug-resistant of most pathogenic organisms is fast becoming a global concern, thus, the discovery of novel active pharmacological compounds against new targets is a matter of urgency. The incorporation of metal ions into organic ligands has introduced metal-organic drugs framework with synergistic effects for novel applications in the biological system. In this research work, metal(II) chloride complexes of copper, nickel and zinc containing methylphenylketone thiosemicarbazone (MPK-TSC) with 2,2’-bipyridine (bipy) were synthesized; they were further characterized by satisfactory microelemental analysis, Fourier Transform InfraRed (FTIR) spectra as well as electronic spectra study. The complexes are proposed to have the formulae [L1ML2(Cl2)] where M=metal ion, L1=methylphenylketone thiosemicarbazone L2=2,2’-bipyridine. The complexes are of 1:2 (metal:ligand) stoichiometry and non-electrolytes in solution, the bidentate nature of the two ligands was evident from the FTIR spectra. The compounds were screened for their antifungal activity against four pathogenic fungi: Aspergillus niger, Penicillium Species, Rizopus and Candida albicans using disc diffusion method. The activities of the complexes have been found to be greater than those of the metal salts and the uncoordinated ligands.

Effect of Chloride Concentration on the Cytotoxicity, Bioavailability, and Bio-Reactivity of Copper and Silver in the Rainbow Trout Gut Cell Line (RTgutGC)

Chloride (Cl-) influences the bioavailability and toxicity of metals in fish, but the mechanisms by which it influences these processes is poorly understood. Here, we investigated the effect of chloride on the cytotoxicity, bioavailability (i.e., accumulation) and bio-reactivity (i.e., induction of mRNA levels of metal responsive genes) of copper (Cu) and silver (Ag) in the rainbow trout gut cell line (RTgutGC). Cells were exposed to metals in media with varying Cl- concentrations (0, 1, 5 and 146 mM). Metal speciation in exposure medium was analyzed using Visual MINTEQ software. Cytotoxicity of AgNO3 and CuSO4 was measured based on two endpoints: metabolic activity and membrane integrity. Cells were exposed to 500 nM of AgNO3 and CuSO4 for 24 hours in respective media to determine metal bioavailability and bioreactivity. Ag speciation changes from free ionic (Ag+) to neutral (AgCl), to negatively charged chloride complexes (AgCl2-, AgCl3-) with increasing Cl- concentration in exposure media whereas Cu speciation remains in two forms (Cu2+ and CuHPO4) across all media. Chloride does not affect Ag bioavailability but decreases metal toxicity and bio-reactivity. Cells exposed to Ag expressed significantly higher metallothionein mRNA levels in low Cl- media (0, 1, and 5 mM) than in high Cl- medium (146 mM). This suggests that chloride complexation reduces silver bio-reactivity and toxicity. Conversely, Cu bioavailability and toxicity were higher in the high chloride medium (146 mM) than in the low Cl- (0, 1, and 5 mM) media, supporting the hypothesis that Cu uptake may occur via a chloride dependent mechanism.

Low Oxidation State Heavy P-Block Metal Compounds Supported by Di(amido) Chelating Ligands

<p>The work presented in this thesis describes the synthesis and stabilisation of heavy p-block elements (defined herein as being those with 5s/p and 6s/p valence electrons) in low oxidation states using sterically demanding ligands based on a di(amido)siloxane framework ([(O{SiMe2N(R)}2]2-, abbrev. [(NONR)]2-). Chapter 1 gives a general introduction to the heavy p-block elements and discusses a number of concepts that define the molecular chemistry of these elements. A brief introduction into low oxidation state main group chemistry is provided and the importance of sterically demanding ligands in this field of research is introduced. The di(amido)siloxane ligand framework utilised in this work is introduced, with common coordination modes and characteristic properties discussed. Chapter 2 discusses the chemistry of low oxidation state bismuth complexes and follows a recent report by our group on the first structurally authenticated bismuth(II) radical •Bi(NONAr). The synthesis of a series of bismuth(III) monochloride species Bi(NONR)Cl (R = tBu, Ph, 2,6-Me2C6H3 (Ar’), 2,6-iPr2C6H3 (Ar) and 2,6-(CHPh2)2-4-tBu-C6H2 (Ar‡)) is discussed, and the steric properties of the ligand systems evaluated. In the case of the R = tBu and Ar‡ derivatives, reduction of the bismuth(III) monochloride gave the dibismuthane [Bi(NONtBu)]2 and bismuth(II) radical •Bi(NONAr‡), respectively. Further reduction of the bismuth centres resulted in the formation of rare and unprecedented multimetallic bismuth compounds containing [Bin]n+ cores. These include the Bi4 cluster compound Bi4(NONAr)2, in which the bismuth atoms exist in an unprecedented mixed valent arrangement and may be assigned oxidation states of 0, +1 or +2, and the tribismuthane cluster [Bi3(NONtBu)2]-, which features the first structurally characterised Bi3 chain. The utility of the di(amido) ligand plays a key role in the formation of many of these compounds, with Bi-N bond cleavage suggested to be a key step in many of the reaction pathways. Chapter 3 discusses the reactivity of the bismuth(II) complexes [Bi(NONtBu)]2, •Bi(NONAr) and •Bi(NONAr‡) which feature either a Bi-Bi bond or a bismuth-centred radical. Initial experiments parallel reported reactivity with halogen radical sources (N-bromosuccinimide or iodine), chalcogens (S, Se, Te) and the stable nitroxyl radical (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), resulting in oxidative addition to generate bismuth(III) complexes. In the latter case, the isolated reaction products, Bi(NONR)(OTEMP), were used to access the catalytic coupling of TEMPO and phenylsilane. Subsequent investigations into the reactivity of the bismuth(II) species revealed the selective activation of white phosphorus (P4) and terminal aromatic alkynes by •Bi(NONAr), generating the bismuth(III) complexes [Bi(NONAr)]2(P4) and [Bi(NONR)]2(HC=C(C6H4-4-X)), respectively. In both cases, a temperature dependent equilibrium is observed. In contrast, the dibismuthane [Bi(NONtBu)]2 and more encumbered bismuth radical •Bi(NONAr‡) do not react with these substrates, demonstrating the importance of the nature of the bismuth centre (i.e. dibismuthane vs. bismuth radical) and ligand bulk on the reactivity of these systems. Chapter 4 describes the synthesis and characterisation of a series of low oxidation state antimony compounds. A series of distibanes supported by the (NONR)-framework were prepared from the reaction of antimony(III) chloride species Sb(NONR)Cl with magnesium(I) reducing agents [(BDIAr§)Mg]2 (Ar§ = 2,4,6-Me3C6H3 or Ar). When R = tBu, Ph or 2,6-Me2C6H3 (Ar’), a distibane [Sb(NONR)]2 is obtained, featuring a Sb-Sb single bond. While the tBu and Ph derivatives contained typical Sb-Sb single bonds, the bonding in the Ar’ derivative is elongated, significantly longer than in all other reported distibanes. The weakness of this bond is highlighted in a reaction with P4, which shows activation of the P4 tetrahedron and P-P bond cleavage. In contrast, reduction of the bulkier Ar derivative (Ar = 2,6-iPr2C6H3) with the magnesium(I) reagents results in formation of the distibene [Sb(NONR)Mg(BDIAr§)]2, featuring a Sb=Sb bond. Chapter 5 describes the synthesis and characterisation of low oxidation state indium compounds supported by the (NONAr)-ligand. A number of indium(III) chloride species supported by either the (NONAr)-ligand or the retro-Brook rearranged (NNOAr)-ligand (NNOAr = [RN{Me2SiO}{Me2SiN(R)}) were synthesised. In all cases, an equivalent of lithium chloride was retained in the molecular structure, allowing isolation of the indate complexes In(NONAr)(μ-Cl)2Li(Et2O)2, [Li(THF)4][In(NONAr)Cl2] and In(NNOAr.Li(THF)3)Cl2. Attempts to reduce these complexes using a hydride source were unsuccessful, instead yielding the corresponding indium(III) hydride species [Li(THF)4][In(NONAr)H2] and In(NNOAr.Li(THF)3)H2, respectively. Reduction of the (NONAr)-supported indium(III) chloride complexes using alkali reducing agents allowed access to the diindane [In(NONAr)]2, featuring an In-In single bond, and the first example of an anionic N-heterocyclic indene. The latter species is isovalent with N-heterocyclic carbenes and is a potential pre-cursor for indium-metal bonding formation. In addition, this compound is of interest as a source of nucleophilic indium. Finally, Chapter 6 provides a summary of the results presented in this thesis and a brief overview of the future direction of this field of research.</p>

Low Oxidation State Heavy P-Block Metal Compounds Supported by Di(amido) Chelating Ligands

<p>The work presented in this thesis describes the synthesis and stabilisation of heavy p-block elements (defined herein as being those with 5s/p and 6s/p valence electrons) in low oxidation states using sterically demanding ligands based on a di(amido)siloxane framework ([(O{SiMe2N(R)}2]2-, abbrev. [(NONR)]2-). Chapter 1 gives a general introduction to the heavy p-block elements and discusses a number of concepts that define the molecular chemistry of these elements. A brief introduction into low oxidation state main group chemistry is provided and the importance of sterically demanding ligands in this field of research is introduced. The di(amido)siloxane ligand framework utilised in this work is introduced, with common coordination modes and characteristic properties discussed. Chapter 2 discusses the chemistry of low oxidation state bismuth complexes and follows a recent report by our group on the first structurally authenticated bismuth(II) radical •Bi(NONAr). The synthesis of a series of bismuth(III) monochloride species Bi(NONR)Cl (R = tBu, Ph, 2,6-Me2C6H3 (Ar’), 2,6-iPr2C6H3 (Ar) and 2,6-(CHPh2)2-4-tBu-C6H2 (Ar‡)) is discussed, and the steric properties of the ligand systems evaluated. In the case of the R = tBu and Ar‡ derivatives, reduction of the bismuth(III) monochloride gave the dibismuthane [Bi(NONtBu)]2 and bismuth(II) radical •Bi(NONAr‡), respectively. Further reduction of the bismuth centres resulted in the formation of rare and unprecedented multimetallic bismuth compounds containing [Bin]n+ cores. These include the Bi4 cluster compound Bi4(NONAr)2, in which the bismuth atoms exist in an unprecedented mixed valent arrangement and may be assigned oxidation states of 0, +1 or +2, and the tribismuthane cluster [Bi3(NONtBu)2]-, which features the first structurally characterised Bi3 chain. The utility of the di(amido) ligand plays a key role in the formation of many of these compounds, with Bi-N bond cleavage suggested to be a key step in many of the reaction pathways. Chapter 3 discusses the reactivity of the bismuth(II) complexes [Bi(NONtBu)]2, •Bi(NONAr) and •Bi(NONAr‡) which feature either a Bi-Bi bond or a bismuth-centred radical. Initial experiments parallel reported reactivity with halogen radical sources (N-bromosuccinimide or iodine), chalcogens (S, Se, Te) and the stable nitroxyl radical (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), resulting in oxidative addition to generate bismuth(III) complexes. In the latter case, the isolated reaction products, Bi(NONR)(OTEMP), were used to access the catalytic coupling of TEMPO and phenylsilane. Subsequent investigations into the reactivity of the bismuth(II) species revealed the selective activation of white phosphorus (P4) and terminal aromatic alkynes by •Bi(NONAr), generating the bismuth(III) complexes [Bi(NONAr)]2(P4) and [Bi(NONR)]2(HC=C(C6H4-4-X)), respectively. In both cases, a temperature dependent equilibrium is observed. In contrast, the dibismuthane [Bi(NONtBu)]2 and more encumbered bismuth radical •Bi(NONAr‡) do not react with these substrates, demonstrating the importance of the nature of the bismuth centre (i.e. dibismuthane vs. bismuth radical) and ligand bulk on the reactivity of these systems. Chapter 4 describes the synthesis and characterisation of a series of low oxidation state antimony compounds. A series of distibanes supported by the (NONR)-framework were prepared from the reaction of antimony(III) chloride species Sb(NONR)Cl with magnesium(I) reducing agents [(BDIAr§)Mg]2 (Ar§ = 2,4,6-Me3C6H3 or Ar). When R = tBu, Ph or 2,6-Me2C6H3 (Ar’), a distibane [Sb(NONR)]2 is obtained, featuring a Sb-Sb single bond. While the tBu and Ph derivatives contained typical Sb-Sb single bonds, the bonding in the Ar’ derivative is elongated, significantly longer than in all other reported distibanes. The weakness of this bond is highlighted in a reaction with P4, which shows activation of the P4 tetrahedron and P-P bond cleavage. In contrast, reduction of the bulkier Ar derivative (Ar = 2,6-iPr2C6H3) with the magnesium(I) reagents results in formation of the distibene [Sb(NONR)Mg(BDIAr§)]2, featuring a Sb=Sb bond. Chapter 5 describes the synthesis and characterisation of low oxidation state indium compounds supported by the (NONAr)-ligand. A number of indium(III) chloride species supported by either the (NONAr)-ligand or the retro-Brook rearranged (NNOAr)-ligand (NNOAr = [RN{Me2SiO}{Me2SiN(R)}) were synthesised. In all cases, an equivalent of lithium chloride was retained in the molecular structure, allowing isolation of the indate complexes In(NONAr)(μ-Cl)2Li(Et2O)2, [Li(THF)4][In(NONAr)Cl2] and In(NNOAr.Li(THF)3)Cl2. Attempts to reduce these complexes using a hydride source were unsuccessful, instead yielding the corresponding indium(III) hydride species [Li(THF)4][In(NONAr)H2] and In(NNOAr.Li(THF)3)H2, respectively. Reduction of the (NONAr)-supported indium(III) chloride complexes using alkali reducing agents allowed access to the diindane [In(NONAr)]2, featuring an In-In single bond, and the first example of an anionic N-heterocyclic indene. The latter species is isovalent with N-heterocyclic carbenes and is a potential pre-cursor for indium-metal bonding formation. In addition, this compound is of interest as a source of nucleophilic indium. Finally, Chapter 6 provides a summary of the results presented in this thesis and a brief overview of the future direction of this field of research.</p>

Hypozonal gold mineralisation in shear zone hosted deposits driven by fault valve action and fluid mixing: the Nalunaq deposit, Greenland

The Nalunaq deposit, Greenland, is a hypozonal, shear zone-hosted, Au deposit. The shear zone has previously been interpreted to have undergone 4 stages of deformation, accompanied by fluid flow,and vein formation. Coupled with previous trapping T estimates, fluid inclusion data are consistent with trapping of fluids with salinities between 28-45 wt. % NaCl eq., from 300-475°C during D2 and D3, with pressure varying between ∼800 and 100Mpa. The range reflects pressure cycling during seismic slip related depressurisation events. D4 fluids were lower salinity and trapped from 200-300°C, at ∼50-200Mpa during late stage normal faulting. The variation in major element chemistry is consistent with ingress of hypersaline, granitoid equilibrated fluids into the shear zone system and mixing with fluids that had reacted with the host metamorphic rocks. D4 stage fluids represent ingress of meteoric fluids into the system. Gold contents in inclusion fluids range from ∼300-10mg/kg. These data are consistent with the high P-T solubility of Au as AuHS(H2S)30 complexes, and Au deposition by decompression and cooling. The high salinities also suggest Au transport as chloride complexes may have been possible. Gold distribution was modified by the release of chemically bound or nanoscale Au during sulphide oxidation at the D4 stage.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5635812

Examining the Modular Synthesis of [Cp*Rh] Monohydrides Supported by Chelating Diphosphine Ligands

[Cp*Rh] hydride complexes are invoked as intermediates in certain catalytic cycles, but few of these species have been successfully prepared and isolated, contributing to a relative shortage of information on the properties of such species. Here, the synthesis, isolation, and characterization of two new [Cp*Rh] hydrides are reported; the hydrides are supported by the chelating diphosphine ligands bis(diphenylphosphino)methane (dppm) and 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos). In both systems, reduction of precursor Rh(III) chloride complexes with Na(Hg) results in clean formation of isolable, formally 18e– Rh(I) species, and subsequent protonation by addition of near-stoichiometric quantities of anilinium triflate to the Rh(I) species returns high yields of the desired monohydride complexes. Single-crystal X-ray diffraction data for these compounds provide evidence of direct Rh–H interactions, confirmed by complementary infrared spectra showing Rh–H stretching frequencies at 1982 cm–1 (for the dppm-supported hydride) and 1936 cm–1 (for the Xantphos-supported hydride). Findings from comprehensive multinuclear NMR experiments reveal the properties of the unique and especially rich spin systems for the dppm-supported hydride; multifrequency NMR studies in concert with spectral simulations enabled full characterization of splitting patterns attributable to couplings involving diastereotopic methylene protons for this complex. Taken together with prior reports of related monohydrides, the results show that the reduction/protonation reaction sequence is modular for preparation of [Cp*Rh] monohydrides supported by diverse diphosphine ligands spanning from four- to eight-membered rhodacycles.