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.     

Metallatriazadiphosphorines of zinc(II), cadmium(II) and mercury(II)

Metallatriazadiphosphorine complexes corresponding to [{N(PPh₂NR)₂}M(OAc)] and [{N(PPh₂NR)₂}₂M], (R = Ph or SiMe₃; M = Zn, Cd or Hg) have been synthesized under strictly anhydrous and inert conditions by the reaction of the acyclic bis-silylated phosphazene ligand, [HN(PPh₂NSiMe₃)₂], or the bis-phenylated phosphazene ligand, [HN(PPh₂NPh)₂], with Zn, Cd and Hg acetate in 1:1 and 2:1 molar ratios. These complexes are highly soluble in common organic solvents, but unstable hydrolytically as well as thermally, even under reduced pressure. Molecular weight determinations in benzene indicated the monomeric nature of these complexes. Further, they have been characterized on the basis of elemental analysis and spectral studies: i.r. and n.m.r. (¹H, ¹³C and ³¹P) that plausibly reveal a trigonal planar and tetrahedral geometry around the metal atom in the complexes.     

Sulfadrug complexes of zinc(II), cadmium(II) and mercury(II)

Summary Zn^II, Cd^II and Hg^II complexes of sulfadrugs,viz., sulfathiazole, sulfadiazine, sulfamerazine and sulfamethazine were prepared and characterized by analytical and spectroscopic data. The complexes are insoluble and melt with decomposition. The drugs act as bidentate ligands yielding polymeric complexes except for the Zn^II(sulfamethazine) complex in which the drug is monodentate.     

Synthesis of norfloxacin compounds with cobalt(II), zinc(II), cadmium(II), and mercury(II)

New compounds of norfloxacin (nfH, C₁₆H₁₈FN₃O₃) with cobalt(II), zinc(II), cadmium(II), and mercury(II) synthesized have the following compositions: Co(nfH-O,O’)₂(H₂O)₂](NO₃)₂, (nfH₂)₂CdCl₄ · 2H₂O, (nfH₂)₂ZnCl₄ · 2H₂O, (nfH₂)₂HgCl₄ · 2H₂O, and (nfH₃)HgCl₄. Their crystallographic parameters were determined. The first listed compound is isostructural to the known zinc analogue. Norfloxacin coordination modes in these complexes are considered.     

Complexes of zinc(II), cadmium(II) and mercury(II) halides with ethylenselenourea

Summary Reaction of zinc(II), cadmium(II) and mercury(II) halides with ethylenselenourea yields complexes of general formula ML₂X₂ where X = Cl, Br, I. On the basis of an i.r. comparison of these complexes and their ethylenthiourea analogues in the 4000-200 cm^–1 range, it appears that the ethylenselenourea complexes are monomeric, tetrahedral and Se-bonded to the metals. The metal-halogen and metal-ligand vibrations above 200 cm^–1 are identified.This work was supported by the National Research Council (C.N.R.) of Italy.     

Simultaneous removal of copper(II), lead(II), zinc(II) and cadmium(II) from aqueous solutions by multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) were used successfully for the removal of heavy metals from aqueous solution. Characterization techniques showed the carbon as nanotubes with an average diameter between 40 and 60 nm and a specific surface area of 61.5 m² g^?1. The effect of carbon nanotubes mass, contact time, metal ions concentration, solution pH, and ionic strength on the adsorption of Cu(II), Pb(II), Cd(II) and Zn(II) by MWCNTs were studied and optimized. The adsorption of the heavy metals from aqueous solution by MWCNTs was studied kinetically using different kinetic models. A pseudo-second order model and the Elovich model were found to be in good agreement with the experimental data. The mechanism of adsorption was studied by the intra-particle diffusion model, and the results showed that intra-particle diffusion was not the slowest of the rate processes that determined the overall order. This model also revealed that the interaction of the metal ions with the MWCNTs surface might have been the most significant rate process. There was a competition among the metal ions for binding of the active sites present on the MWCNTs surface with affinity in the following order: Cu(II) > Zn(II) > Pb(II) > Cd(II).     

Complexes of dicamba with cadmium(II), copper(II), mercury(II), lead(II) and zinc(II)

New solid complexes of a herbicide known as dicamba (3,6-dichloro-2-methoxybenzoic acid) with Pb(II), Cd(II), Cu(II) and Hg(II) of the general formula M(dicamba)₂·xH₂O (M=metal, x=0-2) and Zn₂(OH)(dicamba)₃·2H₂O have been prepared and studied. The complexes have different crystal structures. The carboxylate groups in the lead, cadmium and copper complexes are bidentate, chelating, symmetrical, in Hg(dicamba)₂·2H₂O - unidentate, and in the zinc salt - bidentate, bridging, symmetrical. The anhydrous compounds decompose in three stages, except for the lead salt whose decomposition proceeds in four stages. The main gaseous decomposition products are CO₂, CH₃OH, HCl and H₂O. Trace amounts of compounds containing an aromatic ring were also detected. The final solid decomposition products are oxychlorides of metals and CuO. This revised version was published online in July 2006 with corrections to the Cover Date.     

Kinetics and mechanism of zinc(II), cadmium(II), and mercury(II) incorporation into meso tetrameta-tolueneporphyrin

The kinetics of Zn(II), Cd(II), and Hg(II) incorporation into meso tetrameta-tolueneporphyri n (H₂T(m-CH₃)PP) in acetone have been studied by means of stopped-flow method. A unified reaction mechanism was proposed and the kinetic parameters were obtained by nonlinear least-square methods. The effect of ionic strength (I) on Cd(II)/H₂T(m-CH₃)PP was investigated. It has been found that there is a negative kinetic salt effect and the relationship of rate constants with ionic strength was obtained. Some solvent effects have also been investigated in this article. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 277–283, 1998.     

Novel five- and six-coordinate zinc (II), cadmium (II) and mercury(II) complexes of macrocyclic ligands

Summary Complexes of 2,6-dipicolinic acid hydrazide, DPH, with Zn^II, Cd^II and Hg^II have been prepared and characterized by elemental analysis, i.r. and electronic spectra and by electrical conductance measurements. The ligand is terdentate, having coordination sites at two deprotonated amide-nitrogen and pyridine-nitrogen atoms. The Zn^II and Hg^II complexes are pentacoordinate whereas the Cd^II complexes are hexacoordinate and have trigonal bipyramidal and pseudooctahedral stereochemistries, respectively. The Zn, Cd and Hg ions induce cyclization of DPH complexes upon reaction with-diketones. The complexes of macrocyclic ligands so formed have the same stereochemistries as those of DPH.     

Complexes of 1-methyl-4-mercaptopiperidine with zinc(II), cadmium(II) and mercury(II) halides

The preparation of a series of complexes formed by 1-methyl-4-mercaptopiperidine (AH) and divalent zinc, cadmium and mercury halides is reported together with some spectral and physical properties. The results of a crystallographic study allows to establish the structure of those of formula [M₂(AH)₂X₄]H₂O (M = Zn, Cd, Hg; X = Br, I) consisting of dimers and involving tetrahedral environment with sulphur-bridges for the metal atoms. Polymeric structures are proposed for the complexes of formulae Cd(AH)Cl₂ and Hg₂Cl₄(AH).     

Proton-ligand and metal ligand stability constants ofN-o-chlorophenylbenzohydroxamic acids with manganese(II), nickel(II), copper(II), zinc(II), cadmium(II) and mercury(II)

Summary The thermodynamic proton-ligand and metal ligand stability constants of the newN-o-chlorophenylbenzohydroxamic acids with manganese, nickel, copper, zinc, cadmium and mercury have been determined in 1 : 1 dioxan : water at 25°.The stability of the complexes mostly follow the ligand basicity order and also the metal ion electron affinities as measured by their ionization potential. The stability constants of the metal complexes follow the order: Cu^(II) > Zn^(II) > Ni^(II) > Mn^(II) > Hg^(II) > Cd^(II).     

Chelated complexes of cadmium(II), cobalt(II), copper(II), mercury(II), nickel(II), uranyl(II) and zinc(II) with benzil bis(4-phenylthiosemicarbazone)

Summary Complexes of Co^II, Ni^II, Cu^II, Zn^II, Cd^II, Hg^II and UO ₂ ^II with benzil bis(4-phenylthiosemicarbazone), H₂BPT, have been synthesized and their structures assigned based on elemental analysis, molar conductivity, magnetic susceptibility and spectroscopic measurements. The i.r. spectra suggest that the ligand behaves as a binegative quadridentate (NSSN) (Co^II, Cu^II, Hg^II and UO ₂ ^II complexes) or as a binegative quadridentate-neutral bidentate chelating agent (Ni^II, Zn^II and Cd^II complexes). Octahedral structures for the Co^II and Ni^II complexes and square-planar structure for the Cu^II complex are suggested on the basis of magnetic and spectral evidence. The crystal field parameters (Dq, B and _B) for the Co^II complex are calculated and agree fairly well with the values reported for known octahedral complexes. The ligand can be used for the microdetermination of Ni^II ions of concentration in the 0.4–6×10^–4 mol l^–1 range and the apparent formation constant for the species generated in solution has also been calculated.     

Combined standardless electrochemical method for determination of lead(II), copper(II), and cadmium(II) in aqueous solutions

A combined standardless method (no calibration of the device against standard solutions or use of the method of additives is required) for determination of lead, copper, and cadmium in aqueous solutions is suggested. The method operates on principles of inversion voltammetry and potentiostatic coulometry. It is convenient for automated analysis of technological solutions and wastewater from electroplating and hydrometallurgical shops.     

Polymetallic complexes: Part VI. Schiff base complexes of cobalt(II), copper(II), nickel(II), zinc(II), cadmium(II) and mercury(II)

Summary The doubly bidentate ON-NO donor Schiff base, prepared from salicylaldehyde and 4,4-diaminodiphenylmethane forms complexes with 11 metal: ligand stoichiometric ratios. The cobalt(II), copper(II) and nickel(II) complexes exhibit subnormal magnetic moments. All the six complexes possess high melting points and are sparingly soluble in common organic solvents. A dinuclear octahedral structure is proposed for the cobalt(II), copper(II), nickel(II) and zinc(II) complexes and a dinuclear tetrahedral configuration is suggested for the cadmium(II) and mercury(II) complexes on the basis of analytical, conductance, magnetic susceptibility, molecular weight, i.r. and electronic spectral data.     

Zinc(II), cadmium(II), mercury(II), and ethylmercury(II) complexes of phosphinothiol ligands

Neutral zinc, cadmium, mercury(II), and ethylmercury(II) complexes of a series of phosphinothiol ligands, PhnP(C6H3(SH-2)(R-3))3-n (n = 1, 2; R = H, SiMe3) have been synthesized and characterized by IR and NMR ((1)H, (13)C, and (31)P) spectroscopy, FAB mass spectrometry, and X-ray structural analysis. The compounds [Zn{PhP(C6H4S-2)2}] (1) and [Cd{Ph2PC6H4S-2}2] (2) have been synthesized by electrochemical oxidation of anodic metal (zinc or cadmium) in an acetonitrile solution of the appropriate ligand. The presence of pyridine in the electrolytic cell affords the mixed complexes [Zn{PhP(C6H4S-2)2}(py)] (3) and [Cd{PhP(C6H4S-2)2}(py)] (4). [Hg{Ph2PC6H4S-2}2] (5) and [Hg{Ph2PC6H3(S-2)(SiMe3-3)}2] (6) were obtained by the addition of the appropriate ligand to a solution of mercury(II) acetate in methanol in the presence of triethylamine. [EtHg{Ph2PC6H4S-2}] (7), [EtHg{Ph2P(O)C6H3(S-2)(SiMe3-3)}] (8), [{EtHg}2{PhP(C6H4S-2)2}] (9), and [{EtHg}2{PhP(C6H3(S-2)(SiMe3-3))2}] (10) were obtained by reaction of ethylmercury(II) chloride with the corresponding ligand in methanol. In addition, in the reactions of EtHgCl with Ph2PC6H4SH-2 and with the potentially tridentate ligand PhP(C6H3(SH-2)(SiMe3-3)) 2, cleavage of the Hg-C bond was observed with the formation of [Hg{Ph2PC6H4S-2}2] (5) and [Hg(EtHg) 2{PhP(O)(C6H3(S-2)(SiMe3-3))2}2] (11), respectively, and the corresponding hydrocarbon. The crystal structures of [Zn3{PhP(C6H4S-2)2}2{PhP(O)(C6H4S-2)2}] (1*), [Cd2{Ph2PC6H4S-2}3{Ph2P(O)C6H4S-2}] (2*), 3, 5, 6, [EtHg{Ph2P(O)C6H4S-2}] (7*), 8, 9, [{EtHg}2{PhP(O)(C6H3(S-2)(SiMe3-3))2}] (10*), and 11 are discussed. The molecular structures of 1, 2, 4, 7, and 10 have also been studied by means of density functional theory (DFT) calculations.     

Structural studies of biologically active complexes of zinc(II), cadmium(II), mercury(II) and copper(II) with p-anisaldehyde thiosemicarbozone

p-Anisaldehyde thiosemicarbazone (PAT) has been used to isolate the complex compounds of the general formula [M(PAT)X₂]H₂O where M(II) = Zn, Hg, Cd and Cu, and X = Cl or $\text{1}\text{2}$SO₄. Probable structures for the complex compounds have been proposed on the basis of elemental analysis, conductometric, spectral and magnetic susceptibility data. The toxicity of the isolated complexes and ligand has been evaluated on pathogenic fungus.     

Behavior of cadmium(II) in irradiated aqueous solutions

Behavior of cadmium(II) in aqueous solutions irradiated by accelerated electrons was studied. A concentration of 8.8 × 10⁻⁴ mol L⁻¹ of cadmium dissolved from Cd(NO₃)₂ requires dose of 15 kGy to be effectively removed from the system containing 1 × 10⁻² mol L⁻¹ of HCOOK as a scavenger of OH radicals. The positive effect of deaeration with N₂O or N₂ was observed in the range of lower doses. The addition of solid modifiers (bentonite, active carbon, zeolite, Cu₂O, NiO, TiO₂ and CuO) reduced the effectivity of radiation removal of cadmium. Product of irradiation is CdCO₃. On the contrary, in the system with cadmium dissolved from CdCl₂ radiation reduction takes place. Systems contained organic complexants (ethylene diamine tetraacetic acid–EDTA, citric acid) were also studied. The solutions of Cd(NO₃)₂ containing initial concentration 2.37 × 10⁻⁴ mol L⁻¹ of Cd^II were mixed with 3 × 10⁻⁴ mol L⁻¹ EDTA. In this system the efficient degradation proceeds up to 90% at a dose of 45 kGy with addition of 5 × 10⁻³ mol L⁻¹ carbonate (pH 10.5). The product of irradiation is CdCO₃. The presence of 1 × 10⁻² mol L⁻¹ of HCOOK in the solution is necessary for radiation removal of cadmium complexed with citric acid (1 × 10⁻³ mol L⁻¹) at pH 8. With increasing concentration of HCOOK (up to 5 × 10⁻² mol L⁻¹) decreases the pH value necessary for the radiation induced precipitation of cadmium. The best result was obtained in the system containing zeolite as a solid modifier.     

Zinc (II), cadmium (II) and mercury (II) complexes of 2-methyl-benzothiazole

The following zinc (II), cadmium (II) and mercury (II) complexes of 2-methyl-benzothiazole (2Mebt=L) have been prepared and studied by conductometric methods, i.r. and Raman spectra: ML₂ (M = Zn, X = Cl, I, NO₃; M = Cd, X = NO₃, ClO₄; M = Hg, X = NO₃), ML_1.5X₂ (M = Zn, X = ClO₄ (H₂O); M = Hg, X = ClO₄) and MLX₂ (M = Cd and Hg, X = Cl, Br, I). The ligand is N-bonded when acting as monodentate and N,S-bonded as bridging ligand. The halide, nitrate and perchlorate ions are coordinated.     

Zinc (II), cadmium (II) and mercury (II) complexes of 2-methyl-benzoxazole

The following zinc (II), cadmium (II) and mercury (II) complexes of 2-methyl-benzoxazole (L) have been prepared and studied by conductometric and i.r. methods: MLX₂ (MCd, XCl, Br; MHg, XCl), HgL_1.5X₂ (XBr, ClO₄), ML₂X₂ (MZn, XCl, Br, I, NO₃; MCd, Hg, XI, NO₃), ZnL₃(ClO₄)₂·2H₂O, CdL₃(ClO₄)₂·3H₂O. The frequency decrease of the ligand bands at 1614 and 1573 cm⁻¹ having a ν(CN) and the increase of the ligand band at 918 cm⁻¹ having a ν(CO) contribution indicate that in the complexes the ligand is N-bonded to the metal.