Crystal chemistry of mercury(I) and mercury(I, II) minerals

The crystal structures of 16 mercury(I)- and mercury(I, II)-containing minerals having (Hg-Hg)²⁺ groups are considered. The Hg-Hg and Hg-X bond lengths and the HgHgX angles (X = Cl, Br, I, O, S) are analyzed. A comparative crystal chemical analysis of the environment of Hg atoms is carried out. The Hg-Hg and Hg-X distances vary within 2.43-2.60 and 1.93-2.43 å, respectively; the angles defining the deviation of the X-Hg-Hg-X groups from linearity are from 146 to 177?. In most cases, the coordination environment of the mercury atoms involves the metal atom of the (Hg-Hg)²⁺ dumbbell and the X atom, but in several compounds the coordination number of the mercury atoms increases due to the additional atoms lying 2.5–3.5 å away. In terlinguaite and kuznetsovite, the Hg₃ triangle is rather unusual; in the latter mineral, the Hg-Hg bonds are lengthened to 2.64-2.70 å. The review covers structural data up to May 1997.     

Rhodanine complexes of zinc(II), cadmium(II), mercury(II) and mercury(I)

The following rhodanine (HRd) complexes of zinc(II), cadmium(II), mercury(II) and mercury(I) have been prepared and studied by i.r. spectra: M(Rd)₂(NH₃)₂ (MZn, Cd) with a 4N,2S-six-coordination; Zn₃(Rd)₄(CH₃COO)(OH), Cd₂(Rd)₃(HRd)₃(CH₃COO)(H₂O) in which the acetato anion is bicoordinated; Hg(Rd)₂, Hg₂(HRd)₃(BF₄)₂·0.5(HAc or EtOH), Hg(HRd)(CF₃COO)₂·H₂O in which both the ligands HRd and Rd⁻ are S,N-bonded to the metal; Hg(HRd)₂Cl₂, Hg(HRd)₄(ClO₄)₂ in which the ligand HRd is S-bonded; Hg₃(Rd)₃ · NH₃ with S,N-bonded Rd⁻ ligand.     

Thermal decomposition of silver(I) and mercury(I) anthranilates and salicyloaldoximates

The processes of thermal decomposition of silver(I) and mercury(I) anthranilates and salicyloaldoximates were studied. Thermal, chemical and X-ray analyses and infrared spectroscopy were used to determine the mechanisms of decomposition of these complexes. The factor determining the decomposition is the character of the Ag⁺ and Hg ₂ ²⁺ ions, which are easily reduced to free metals. The final reaction product of the compounds of silver is the pure metal; the compounds of mercury are volatilized completely when heated.     

Thermal properties of mercury(II) and palladium(II) purine and pyrimidine complexes

Six solid Pd(II) and Hg(II) complexes of some purines and pyrimidines have been prepared and characterized by elemental analyses, IR, UV–Vis spectra, magnetic measurements, and thermal analyses. The data suggest tetrahedral and square planar geometries for mercury and palladium complexes, respectively. The thermal behavior of the complexes has been studied applying TG, DTA, and DSC techniques, and the thermodynamic parameters and mechanisms of the decompositions were evaluated. The ?S* values of the decomposition steps of the metal complexes indicated that the activated fragments have more ordered structure than the undecomposed complexes, and/or the decomposition reactions are slow. The thermal processes proceeded in complicated mechanisms where the bond between the central metal ion and the ligands dissociates after losing small molecules such as H₂O, HCl or C=O. The palladium adenine complex is ended with the metal as a final product. However, the thermal reactions of the other five palladium and mercury pyrimidines complexes are ended with metal bonded to O, N, or S of the pyrimidine ring.     

Thermal characterization of mercury(II) bis(dialkyldithiocarbamate) complexes

Summary Solid-state M-4-MeO-Bz compounds, where M stands for bivalent Mn, Co, Ni, Cu and Zn and 4-MeO-Bz is 4-methoxybenzoate, have been synthesized. Simultaneous thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy, elemental analysis and complexometry were used to characterize and to study the thermal behaviour of these compounds. The results led to have information about the composition, dehydration, thermal stability and thermal decomposition of the isolated compounds.     

Thermal decomposition of complexes of cadmium(II) and mercury(II) with triphenylphosphanes

A series of substituted triphenylphosphane complexes of the type CdL₂X₂ (L= triorthotolylphosphane or trimetatolylphosphane; X=Cl⁻, Br⁻ or I⁻) and HgL₂X₂ (L=triphenylphosphane or triorthotolylphosphane) was prepared fresh. The thermal decomposition was carried out in air with heating rate programmed at 10°C min⁻¹ and it revealed that the complexes with ortho derivative were less stable and the triphenylphosphane moiety leaves along with halogen in the first step. All the complexes were stable up to 210°C. However, the stability order of the tetrahedral complexes was X=Cl>Br. Values of n, E, lnA and ΔS ^# have been approximated and compared. Complexes having Br have higher E _a, lnA and ΔS ^# values than that having Cl.     

Multiplexed analysis of silver(I) and mercury(II) ions using oligonucletide-metal nanoparticle conjugates

A colorimetric assay has been developed for the simultaneous selective detection of silver(I) and mercury(II) ions utilizing metal nanoparticles (NPs) as sensing element based on their unique surface plasmon resonance properties. In this method, sulfhydryl group modified cytosine-(C)-rich ssDNA (SH-C-ssDNA) was self-assembled on gold nanoparticles (AuNPs) to produce the AuNPs-C-ssDNA complex, and sulfhydryl group modified thymine-(T)-rich ssDNA (SH-T-ssDNA) was self-assembled on silver nanoparticles (AgNPs) to produce the AgNPs-T-ssDNA complex. Oligonucleotides (SH-C-ssDNA or SH-T-ssDNA) could enhance the AuNPs or AgNPs against salt-induced aggregation. However, the presence of silver(I) ions (Ag(+)) in the complex of ssDNA-AuNPs would reduce the stability of AuNPs due to the formation of Ag(+) mediated C-Ag(+)-C base pairs accompanied with the AuNPs color change from red to purple or even to dark blue. Moreover, the presence of mercury(II) ions (Hg(2+)) would also reduce the stability of AgNPs due to the formation of Hg(2+) mediated T-Hg(2+)-T base pairs accompanied with the AgNPs color change from yellow to brown, then to dark purple. The presence of both Ag(+) and Hg(2+) will reduce the stability of both AuNPs and AgNPs and cause the visible color change. As a result, Ag(+) and Hg(2+) could be detected qualitatively and quantitatively by the naked eye or by UV-vis spectral measurement. The lowest detectable concentration of a 5 nM mixture of Ag(+) and Hg(2+) in the river water was gotten by the UV-vis spectral measurement.     

Titrimetric analysis of total mercury ions including mercury(I) ions

A systematic analytical method is proposed and applied to directly determine the total concentration of Hg(II) and Hg(I) ions in water. Experimental results demonstrate that this method provides a low detection limit of 0.05 mM and small relative error within 1.5% in an ion concentration range of 0.2–50 mM. The technique is especially applicable for sample solutions that the traditional titration method like Volhard and EDTA complexation titrimetry could not analyze directly. This method could be employed to analyze solutions in any ratio of Hg(II) and Hg(I) ions including pure Hg(II) or pure Hg(I) ions, exhibiting several advantages, such as simple operation, good reproducibility, and low cost. Correspondence: Xin-Gui Li, Key Laboratory of Advanced Civil Engineering Materials, Institute of Materials Chemistry, College of Materials Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China.     

Titrimetric analysis of total mercury ions including mercury(I) ions

A systematic analytical method is proposed and applied to directly determine the total concentration of Hg(II) and Hg(I) ions in water. Experimental results demonstrate that this method provides a low detection limit of 0.05 mM and small relative error within 1.5% in an ion concentration range of 0.2–50 mM. The technique is especially applicable for sample solutions that the traditional titration method like Volhard and EDTA complexation titrimetry could not analyze directly. This method could be employed to analyze solutions in any ratio of Hg(II) and Hg(I) ions including pure Hg(II) or pure Hg(I) ions, exhibiting several advantages, such as simple operation, good reproducibility, and low cost.     

Determination of sulfite by reaction with mercury(I) chloride and spectrophotometric measurement of mercury(II) complexes

Sulfite ion was determined in the 0.4 to 12-ppm range by reaction with insoluble mercury(I) chloride to form the soluble Hg(SO₃)₂^staggered2? ion and elemental mercury. The uv absorption of the sulfite complex or an anion species, HgX₄^staggered2?, formed on adding an excess of KBr, KCl, KI, or KSCN is measured. The mercury(II) in solution can also be determined by lowering the pH, adding KCl, and forming the crystal violet adduct of the HgCl₃^staggered? ion. This adduct is extracted into benzene and the absorbance measured at 605 nm.     

Flow potentiometric stripping analysis for mercury(II)

The optimum experimental conditions, with respect to sample and stripping solution composition, in computerised flow potentiometric stripping analysis for mercury(II) with a gold working electrode are described. When pre-electrolysis -was done in a sample to which ammonia and iodide had been added and stripping was done in an acidified bromide solution containing chromium(VI), a detection limit of 2 nM (0.4 μg kg^-1) was obtained after 90 s of pre-electrolysis, the dynamic range being almost three decades. Copper(II) interfered when present in a 1000-fold excess and silver(I) when present in a 5-fold excess over mercury(II).     

Measurement of methyl mercury (I) and mercury (II) in fish tissues and sediments by HPLC-ICPMS and HPLC-HGAAS

A procedure for the extraction and determination of methyl mercury and mercury (II) in fish muscle tissues and sediment samples is presented. The procedure involves extraction with 5% (v/v) 2-mercaptoethanol, separation and determination of mercury species by HPLC-ICPMS using a Perkin-Elmer 3 μm C8 (33 mm × 3 mm) column and a mobile phase 3 containing 0.5% (v/v) 2-mercaptoethanol and 5% (v/v) CH₃OH (pH 5.5) at a flow rate 1.5 ml min⁻¹ and a temperature of 25 °C. Calibration curves for methyl mercury (I) and mercury (II) standards were linear in the range of 0-100 μg l⁻¹ (r² = 0.9990 and r² = 0.9995 respectively). The lowest measurable mercury was 0.4 μg l⁻¹ which corresponds to 0.01 μg g⁻¹ in fish tissues and sediments. Methyl mercury concentrations measured in biological certified reference materials, NRCC DORM - 2 Dogfish muscle (4.4 ± 0.8 μg g⁻¹), NRCC Dolt - 3 Dogfish liver (1.55 ± 0.09 μg g⁻¹), NIST RM 50 Albacore Tuna (0.89 ± 0.08 μg g⁻¹) and IRMM IMEP-20 Tuna fish (3.6 ± 0.6 μg g⁻¹) were in agreement with the certified value (4.47 ± 0.32 μg g⁻¹, 1.59 ± 0.12 μg g⁻¹, 0.87 ± 0.03 μg g⁻¹, 4.24 ± 0.27 μg g⁻¹ respectively). For the sediment reference material ERM CC 580, a methyl mercury concentration of 0.070 ± 0.002 μg g⁻¹ was measured which corresponds to an extraction efficiency of 92 ± 3% of certified values (0.076 ± 0.04 μg g⁻¹) but within the range of published values (0.040-0.084 μg g⁻¹; mean ± s.d.: 0.073 ± 0.05 μg g⁻¹, n = 40) for this material. The extraction procedure for the fish tissues was also compared against an enzymatic extraction using Protease type XIV that has been previously published and similar results were obtained. The use of HPLC-HGAAS with a Phenomenox 5 μm Luna C18 (250 mm × 4.6 mm) column and a mobile phase containing 0.06 mol l⁻¹ ammonium acetate (Merck Pty Limited, Australia) in 5% (v/v) methanol and 0.1% (w/v) l-cysteine at 25 °C was evaluated as a complementary alternative to HPLC-ICPMS for the measurement of mercury species in fish tissues. The lowest measurable mercury concentration was 2 μg l⁻¹ and this corresponds to 0.1 μg g⁻¹ in fish tissues. Analysis of enzymatic extracts analysed by HPLC-HGAAS and HPLC-ICPMS gave equivalent results.     

New N-heterocyclic carbene mercury(II) and silver(I) complexes

The complexes [1-(9-anthracenylmethyl)-3-octylimy]₂Hg[HgCl₄] (2a) (imy = imidazol-2-ylidene) and [1-(9-anthracenylmethyl)-3-butylbimy]₂AgPF₆ (2b) (bimy = benzimidazol-2-ylidene) have been prepared and characterized. Crystal packing of complex 2a revealed that 1D polymeric chains are formed by [1-(9-anthracenylmethyl)-3-octylimy]Hg and [HgCl₄]²⁻ through weak Hg…Cl bonds. The packing diagram of 2b showed that 1D supramolecular chains are formed by both benzimidazole ring head to tail π–π stacking interactions and anthracene ring face-to-face π–π stacking interactions.     

Thermal decomposition of potassium salts of cyano-halogeno complexes of mercury(II)

The thermal decompositions of Hg(CN)₂, K₂Hg(CN)₄, KHg(CN)₂Cl · H₂O KHg(CN)₂Br and KHg(CN)₂I were studied. The results showed that each of the studied complexes decomposes at a lower temperature than Hg(CN)₂ itself. The halogen-containing complexes decompose in two ways. In KHg(CN)₂Cl · H₂O the Hg-CN bond is first broken, and then Hg₂Cl₂, (CN)₂ and KCN are formed. The first step in the decomposition of KHg(CN)₂Br and KHg(CN)₂I, on the other hand, is the decomposition to Hg(CN)₂ and KBr or KI.     

The thermal properties of inorganic compounds: I. Some mercury(I) and (II) compounds

The TG and DTA (DSC) curves of the yellow and red forms of mercury(II) oxide, mercury(II) chloride, bromide and iodide, and mercury(I) iodide are reported. A lower initial procedural dissociation temperature, 400°C, was observed for the yellow form of HgO versus 460°C for the red form. This lower value is consistent with the postulate of a smaller particle size for the yellow form. Although only sublimation behavior was indicated in the DSC curves of the mercury(II) halides, by the use of sealed-tube DTA, fusion transitions were also observed. These data may be of unusual importance in ecological and environmental problems.     

Copper(I) and mercury(II) halide complexes of 1,2-bis(diphenylthioylphosphino)hydrazine

The reaction of 1,2-bis(diphenylthioylphosphino)hydrazine (L) with copper(I) and mercury(II) halides affords the complexes, [{CuLX}₂] (X = I, Br or Cl), [HgLX₂] (X = Cl or Br) and the tetrametallic complex, [{L(HgI₂)₂}₂]. Single crystal X-ray structures have been performed on the uncoordinated ligand, L, as well as the complexes [{CuLX}₂] (X = I, Br and Cl), [HgLBr₂] and [{L(HgI₂)₂}₂. The molecules of L exist as dimers as a result of pairs of N–HS hydrogen bonds. The copper(I) complexes are centrosymmetric dimetallic species, the two copper atoms being bridged by L and the X atoms. In all cases the coordination sphere around the Cu atoms is approximately trigonal pyramidal with an ‘S₂X₂’ donor set. The complex, [HgLBr₂], is a distorted tetrahedral monomer with an ‘S₂Br₂’ donor set and L acting as a bidentate thus forming a seven-membered chelate ring. The tetramercury iodo complex, [{L(HgI₂)₂}₂], contains two ‘L(HgI₂)₂’ units linked centrosymmetrically via an I atom from each moiety. The geometry around the Hg atoms is distorted tetrahedral. The influence of hydrogen bonding between the hydrazine backbone hydrogens of L and the coordinated halide ions in for the structures of the metal complexes is discussed.     

Catalytic amperometric and catalytic constant-current potentiometric titrations of silver(I), palladium(II) and mercury(II)

Amperometry and constant-current potentiometry were used to follow the course of catalytic titrations of silver(I), palladium(II), and mercury(II) with potassium iodide. The Ce(IV)As(III) and Ce(IV)Sb(III) systems in the presence of sulphuric acid were used as indicator reactions. The possibilities of application of platinum, palladium, gold, graphite, and glassy-carbon indicator electrodes were investigated. Graphite appeared to be somewhat more advantageous than the other electrode materials. The effect of concentration of the components of the indicator reactions, the presence of organic solvents and acids on the shape of the catalytic titration curves was studied. Amounts of 30-3000 mug of silver(I) nitrate, 90-900 mug of palladium(II) chloride, 130-1300 mug of mercury(II) chloride, and 150-1500 mug of mercury(II) nitrate were determined with a relative standard deviation less than 1.0%. The results obtained were in good agreement with those of comparable methods. The catalytic titration method developed was applied to determination of mercury in Unguentum Hydrargyri.