Sequestering ability of some chelating agents towards methylmercury(II)

A study on the interactions between CH₃Hg⁺ and some S, N and O donor ligands (2-mercaptopropanoic acid (thiolactic acid (H₂ TLA)), 3-mercaptopropanoic acid (H₂ MPA), 2-mercaptosuccinic acid (thiomalic acid (H₃ TMA)), d,l-penicillamine (H₂ PSH), l-cysteine (H₂ CYS), glutathione (H₃ GSH), N,N′-bis(3-aminopropyl)-1-4-diaminobutane (spermine (SPER)), 1,2,3,4,5,6-benzenehexacarboxylic acid (mellitic acid (H₆ MLT)) and ethylenediaminetetraacetic acid (H₄ EDTA)) is reported. The speciation models in aqueous solution and the possible structures of the complexes formed are discussed on the basis of potentiometric, calorimetric, UV spectrophotometric and electrospray mass spectrometric results. For the CH₃Hg⁺–S donor ligand systems, the formation of ML^1–z and MLH^2–z complex species is observed, together with a diprotonated MLH ₂ ^3–z species for CYS ^2?, PSH ^2? and GSH ^3? and the mixed hydrolytic one ML(OH)^?z for TLA ^2? and MPA ^2?. The dependence of the stability on ionic strength and on temperature is also analysed. In the other CH₃Hg⁺-L systems (L?=?MLT ^6?, SPER and EDTA ^4?), ML^1–z , MLH^2–z and MLH₂ ^3–z complex species are formed, together with the MLH₃ ^4–z species for SPER, the mixed hydrolytic ML(OH)^–z one for SPER and EDTA, and the M₂L^2–z for EDTA only. On the basis of the speciation models proposed, the sequestering ability of the ligands towards methylmercury(II) cation is evaluated. All S donor ligands show a good sequestering power (at 10^?11?mol?L^?1 level, in the pH range 4 to 8) following the trend MPA ^2??<?PSH ^2??<?GSH ^3??<?TLA ^2??<?CYS ^2??<?TMA ^3?, while significantly lower is the sequestering ability of MLT, SPER and EDTA (at 10^?3–10^?5?mol?L^?1 level, in the pH range 4 to 8).

A new class of peptide chelating agents towards copper(II) ions

Potentiometric and spectroscopic data including CD and EPR results as well as theoretical calculations have shown that the insertion of the tetrazole ring [ψ(CN₄)] in the tetraalanine sequence leads to a very effective peptide chelating agent towards Cu(II) ions. The [ψ(CN₄)] moiety induces a specific peptide conformation which favours the formation of one or two stable chelating rings stabilising a bent structure, with the coordination of 1N-type in CuL or 3N-type in both CuH₋₁L and CuH₋₂L species. It is worth noting that the Cu(II)N_tetr bond does not undergo the hydrolysis process even at high pH although the N_tetr donor is weakly basic.     

New Reactivity of the Uranyl(VI) Ion

The chemistry of the uranyl ion ([UO₂]²⁺) has evolved remarkably over the past few years, with unexpected reactivity observed that challenge our understanding of this ion, and of actinides in general. This review highlights some recent advances in the field, focussing on the organometallic chemistry of the uranyl moiety, which is not well developed in comparison to lower oxidation states of uranium. The use of uranyl as a catalyst is highlighted and the newly developed supramolecular chemistry is described. The uranyl oxygen atoms have been considered as inert, but recent work has shown that is not necessarily the case and is discussed herein. Finally, reduction to the [UO₂]⁺ ion will be discussed.     

Reactivity of the 16e (p-cymene)Ru half-sandwich complex containing a chelating 1,2-dicarba-closo-dodecaborane-1,2-dithiolate ligand towards diynes

The reactions of the 16e half-sandwich complex (p-cymene)Ru(S(2)C(2)B(10)H(10)) (Ru16e) with 1,4-diethynylbenzene (L1), 3',6-diethynyl-1,1'-binaphthyl-2,7'-diyl diacetate (L2), 2-bromo-5-ethynylthiophene (L3) and 2,5-diethynylthiophene (L4) lead to 18e mononuclear complexes (p-cymene)Ru(S(2)C(2)B(10)H(9))(H(2)CCPhC≡CH) (1), (p-cymene)Ru(S(2)C(2)B(10)H(9))[H(2)CC(C(24)H(16)O(4))C≡CH] (2), (p-cymene)Ru(S(2)C(2)B(10)H(9)) [H(2)CC(C(4)H(2)S)Br] (3) and (p-cymene)Ru(S(2)C(2)B(10)H(9)) [H(2)CC(C(4)H(2)S)C≡CH] (4), respectively. In all of them, metal-induced B-H activation has occurred, which leads to a stable Ru-B bond, and the structures take a cisoid arrangement. Only in the case of L4, the binuclear complexes [(p-cymene)Ru(S(2)C(2)B(10)H(9))](2)[H(2)CC(C(4)H(2)S)CCH(2)] (5a and 5b) are observed, which are conformational isomers generated by the differing orientations of the p-cymene unit. 4 can be readily converted to the complex (p-cymene)Ru(S(2)C(2)B(10)H(9))[H(2)CC(C(4)H(2)S)COCH(3)] (6) in the presence of silica and H(2)O. All of these products 1-6 were characterized by NMR, IR, elemental analysis and mass spectrometry. The structures of 1, 3, and 5a were also determined by single-crystal X-ray diffraction analysis.     

New organically templated copper(I) sulfites: the role of sulfite anion as both soft and hard ligand

Two new organically templated layered copper(I) sulfites, namely, {H2pip}{Cu3(CN)3(SO3)} (1) and {H2pip}{NaCu2(SO3)2Br(H2O)}.2H2O (2) (pip = piperazine), have been synthesized by hydrothermal reactions of copper(I) cyanide or copper(I) bromide with NaHSO3 and piperazine. Both compounds exhibit a layered structure. The 2D layer of {Cu3(CN)3(SO3)}2- in 1 is composed of 1D chains of copper(I) cyanide interconnected by sulfite anions via both Cu-S and Cu-O bonds, whereas the 2D layer of {NaCu2(SO3)2Br}2- in 2 is formed by 1D chains of copper(I) bromide and 1D sodium(I) aqua chains that are interconnected by sulfite anions via Na-O, Cu-S, and Cu-O bonds. Chemical bonding in 1 and 2 has been also investigated by theoretical calculations based on DFT methods.     

Imidotungsten(VI) complexes with chelating amino and imino phenolates

The reaction of WOCl(4) with 2,4-di-tert-butyl-6-((isopropylamino)methyl)phenol followed by the reaction with phenyl isocyanate leads to the formation of imidotungsten(VI) complex [W(NPh)Cl(3)(OC(6)H(3)(CH(2)NH-i-Pr)-2-t-Bu(2)-4,6)] 4 with a chelating aminophenolate ligand. When the same procedure was applied using aminophenols with bulkier substituents in the amino group, the final product was an unexpected Schiff-base complex [W(NPh)Cl(3)(OC(6)H(3)(CH=NPh)-2-t-Bu(2)-4,6)] 5, where the ligand is derived from 2,4-di-tert-butyl-6-((phenylimino)methyl)phenol. Complex 5 is also formed in the thermal degradation of 4. On the whole, 5 appears to be formed by a disproportionation of intermediate compounds, which are analogous to complex 4. The solid-state structures of 4 and 5 have been determined by X-ray crystallography whereas the solution structures were studied by (1)H and (13)C NMR.     

三(三甲硅基)环戊二烯基三羰基钼负离子的反应性

三(三甲硅基)环戊二烯基三羰基钼负离子锂盐[{η^5-(Me~3Si)~3C~5H~2}Mo(CO)~3]^-Li^+(1), 分别与MeI、phCH~2Cl及ClCH~2COOC~2H~5反应生成相应的烃基化钼衍生物[{η^5-(Me~3Si)~3C~5H~2}Mo(CO)~3R,] (R=-CH~3, 2; -CH~2ph, 3;-CH~2COOC~2H~5, 4)。1与PCl~3反应除得到预期的钼氯化物[{η^5-(Me~3Si)~3C~5H~2}Mo(CO)~3Cl](5)外, 主要得到钼磷氯化物[{η^5-(Me~3Si)~3C~5H~2}Mo(CO)~3PCl~2] 6; 1与碘反应得到钼碘化物[{η^5-(Me~3Si)~3C~5H~2}Mo(CO)~3I] 7; 1与HOAc作用后分别和CCl~4、NBS室温反应, 仅分离到脱去一个Me~3Si的钼卤化物[{η^5-(Me~3Si)~2C~5H~2}Mo(CO)~3X], (X:Cl, 8; Br, 9)。     

Separation and concentration of molybdenum(VI) and tungsten(VI) with chelating ion-exchange resins containing sulphur ligands

Three chelating ion-exchange resins based on macroreticular polyacrylonitrile-divinylbenzene copolymers with thioglycollic acid and cysteine as functional groups have been tested for separation of molybdenum(VI) and tungsten(VI). On a short column of the thioglycollic acid resin, molybdenum(VI) and tungsten(VI) can be selectively sorbed from pH-4.3 acetate buffer and eluted with 2M hydrochloric acid and a mixture of 0.1M sodium hydroxide and 0.1M sodium chloride, respectively, with quantitative recovery even at very low concentrations. Simulated sea-water samples have been analysed.     

X-Ray crystal structure of the tris(acetato)dioxoosmate(VI) anion

X-ray crystallographic study of K[OsO₂(O₂CMe)₃]· 2MeCO₂H shows that the anion has cis dioxo, one chelate and two trans monodentate acetato groups.     

Dinitrogen complexes of chromium(III) with chelating agents

Summary Two new dinitrogen complexes of Cr^III with EDTA and CDTA have been prepared from reaction of [Cr(Y-H)H₂O] (Y = EDTA, CDTA) with sodium azide in aqueous solution. Both complexes exhibit characteristic bands at 2070 cm^–1 in the i.r. spectra corresponding to (N₂). The 10 Dq and B parameters were calculated from the u.v. visible spectra.     

New imine-phosphine chelating agents and their molybdenum(O) derivatives

The aldehyde o-Ph₂PC₆H₄CHO condenses with a variety of functionalized amines to afford several new ligand which form stable mono- and bimetallic complexes with molybdenum(O).     

The reactions between tetrachloroplatinate(II) anion and bidentate sulphur-nitrogen chelating agents: A direct route for the synthesis of the neutral dichloro species

A direct route for the synthesis of the neutral dichloro complexes [Pt(NS)Cl₂], (NS = 2-[(ethylthio)methyl]pyridine and 2-[(phenylthio)methyl]pyridine) in dimethylformamide, which avoids the formation of bis-chelate cations, is reported.     

Reactivity of superoxide anion radical with a perchlorotriphenylmethyl (trityl) radical

The reaction of superoxide radical with a tricarboxylate derivative of perchlorotriphenylmethyl radical (PTM-TC) is studied. PTM-TC is a stable ("inert") free radical, which gives a single sharp electron paramagnetic resonance (EPR) peak in aqueous solutions. PTM-TC also gives a characteristic optical absorption at 380 nm. Superoxide, on reaction with PTM-TC, induced a decrease in the intensity of the EPR signal and optical absorption of PTM-TC at 380 nm. The signal loss was specific to superoxide and linearly dependent on the superoxide flux in the system. Competitive kinetics experiments revealed that PTM-TC reacts with superoxide with an apparent second-order rate constant of 8.3x10(8) M(-1) s(-1). Electrochemical and mass spectrometric analyses of the reaction suggested the formation of perchlorotriphenylmethane and molecular oxygen as products. The high sensitivity of detection of PTM-TC combined with the high rate constant of the reaction of superoxide with PTM-TC may offer a potential opportunity for measurement of superoxide in biological systems. In conclusion, the PTM-TC molecule has high sensitivity and specificity for superoxide radicals and thus may enable quantitative detection of superoxide generation in biological systems using EPR and/or spectrophotometric methods.     

Solvent extraction of chromium(VI) from base metal ions with diphenyl-2-pyridylmethane as a liquid anion exchanger

The extraction of chromium(VI) from aqueous hydrochloric, nitric and sulfuric acid solutions by diphenyl-2-pyridylmethane(DPPM) dissolved in chloroform has been studied. Chromium(VI) is quantitatively extracted from hydrochloric acid solutions in the range 0.1–1M. With increasing acid concentration, the extraction of chromium diminishes and in concentrated acid solutions practically all the chromium remains in the aqueous phase. The quantitative back-extraction of chromium from the organic phase is possible with HCl or HNO₃ at concentrations higher than 5M through the use of reducing agents. The composition of the extracted chromium(VI) species was studied in solution. The complexes (DPPMH)⁺HCrO ₄ ⁻ and (DPPMH)₂Cr₂O ₇ ⁻ are extracted for tracer and macro amounts of chromium(VI) respectively. The data have been utilized for the separation of chromium(VI) from base metal ions.     

Further links between the maximum hardness principle and the hard/soft acid/base principle: insights from hard/soft exchange reactions

Ayers, Parr, and Pearson recently showed that insight into the hard/soft acid/base (HSAB) principle could be obtained by analyzing the energy of reactions in hard/soft exchange reactions, i.e., reactions in which a soft acid replaces a hard acid or a soft base replaces a hard base [J. Chem. Phys., 2006, 124, 194107]. We show, in accord with the maximum hardness principle, that the hardness increases for favorable hard/soft exchange reactions and decreases when the HSAB principle indicates that hard/soft exchange reactions are unfavorable. This extends the previous work of the authors, which treated only the "double hard/soft exchange" reaction [P. K. Chattaraj and P. W. Ayers, J. Chem. Phys., 2005, 123, 086101]. We also discuss two different approaches to computing the hardness of molecules from the hardness of the composing fragments, and explain how the results differ. In the present context, it seems that the arithmetic mean of fragment softnesses is the preferable definition.     

Chelating behavior of macroreticular hydroxamic acid resin towards molybdenum(VI), tungsten(VI), uranium(VI) and vanadium(V)

Summary The properties and behaviour of the hydroxamic acid resin have been studied and shown to be an highly selective resin for molybdenum(VI), tungsten(VI), uranium(VI) and vanadium(V) ions. The stability constants of these metal ion complexes with the resin have been determined. The sorption and desorption characteristics of these metal ions on this resin and the methods for the separation of these metal ions from each other on a short column of such resin were also developed.

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Komplexierungsverhalten von makroretikularem Hydroxamsäureharz gegenüber Molybdän(VI), Wolfram(VI), Uran(VI) und Vanadium(V)

Zusammenfassung Die Eigenschaften und das Verhalten von Hydroxamsäureharz wurden untersucht. Das Harz erwies sich als hochselektiv für Mo(VI), W(VI), U(VI) und V(V). Die Stabilitätskonstanten der Komplexe wurden bestimmt, die Sorptions- und Desorptionscharakteristica wurden untersucht und Trennungsmethoden für die genannten Ionen an einer kurzen Säule entwickelt.

     

Uranium(VI) removal from aqueous solutions by a chelating fiber

Journal of Radioanalytical and Nuclear Chemistry - A chelating fiber (CF), containing amine and hydroxyl groups, has been characterized and used as an adsorbent for the removal of U(VI) from...     

Chromium(VI) transport through the Raipore 1030 anion exchange membrane

The flat sheet Raipore R1030 anion exchange membrane has been evaluated as a sample interface in an optical sensor for Cr(VI) monitoring. The R1030 is an anion exchange membrane containing quaternary ammonium groups. The Donnan dialysis (DD) that takes place has been enhanced with facilitated transport of Cr(VI) anions by using a 1,5-diphenylcarbazide (DPC) solution as stripping phase. The DPC acts as a reducing reagent for Cr(VI), and as a complexing reagent for the generated Cr(III). The Cr(III) complex is a strongly absorbing species, and this is the basis of the optical detection. The effect of chemical parameters on Cr(VI) transport has been evaluated. Experiments with UV-VIS detection have shown that the membrane R1030-DPC system exhibits features suitable for Cr(VI) optical sensing. A simplified model based on a kinetic approach is reported describing the transport mechanism of the chemically facilitated DD process.     

Sequestering ability of polycarboxylic ligands towards dioxouranium(VI)

In this paper we report a comparison on the sequestering ability of some polycarboxylic ligands towards dioxouranium(VI) (UO(2)(2+), uranyl). Ligands taken into account are mono- (acetate), di- (oxalate, malonate, succinate and azelate), tri- (1,2,3-propanetricarboxylate) and hexa-carboxylate (1,2,3,4,5,6-benzenehexacarboxylate). The sequestering ability of polycarboxylic ligands towards UO(2)(2+) was quantified by a new approach expressed by means of a sigmoid Boltzman type equation and of a empirical parameters (pL(50)) which defines the amount of ligand necessary to sequester 50% of the total UO(2)(2+) concentration. A fairly linear correlation was obtained between pL(50) or log K(110) (log K(110) refers to the equilibrium: UO(2)(2+)+L(z-)=UO(2)L((2-z)); L=generic ligand) and the polyanion charges. In order to complete the picture, a tetra-carboxylate ligand (1,2,3,4-butanetetracarboxylate) was studied in NaCl aqueous solutions at 0相似文献   

Synthesis of phosphorus-modified poly(styrene-co-divinylbenzene) chelating resin and its adsorption properties of uranium(VI)

A new phosphorus-modified poly(styrene-co-divinylbenzene) chelating resin (PS–N–P) was synthesized by P,P-dichlorophenylphosphine oxide modified commercially available ammoniated polystyrene beads, and characterized by Fourier transform infrared spectroscopy and elemental analysis. The adsorption properties of PS–N–P toward U(VI) from aqueous solution were evaluated using batch adsorption method. The effects of the contact time, temperature, pH and initial uranium concentration on uranium(VI) uptake were investigated. The results show that the maximum adsorption capacity (97.60 mg/g) and the maximum adsorption rate (99.72 %) were observed at the pH 5.0 and 318 K with initial U(VI) concentration 100 mg/L and adsorbent dose 1 g/L. Adsorption equilibrium was achieved in approximately 4 h. Adsorption kinetics studied by pseudo second-order model stated that the adsorption was the rate-limiting step (chemisorption). U(VI) adsorption was found to barely decrease with the increase in ionic strength. Equilibrium data were best modeled by the Langmuir isotherm. The thermodynamic parameters such as ?G ₀, ?H ₀ and ?S ₀ were derived to predict the nature of adsorption. Adsorbed U(VI) ions on PS–N–P resin were desorbed effectively (about 99.39 %) by 5 % NaOH–10 % NaCl. The synthesized resin was suitable for repeated use.