On the Reaction of Triaryl Trithioarsenites, (ArS)3As,with Iodine

Iodine in dry nonprotic solvents oxidizes triaryl trithioarsenites, (ArS)₃As, to As(III) iodide, AsI₃, and disulfides, ArSSAr. The reaction most likely involves arylsulfenyl iodide, ArSI, as an intermediate. With triphenyl and tris(4-chlorophenyl) trithioarsenites, AsI₃ is prepared in very good yields. When the disulfide, which is produced, has MeCONH─ or ─NH─CMe₂─OH groups, then it acts as a Lewis base towards AsI₃ forming complexes with stoichiometry 2AsI₃·3ArSSAr. Probable coordination modes of the AsI₃ are discussed.     

On the Reaction of Triaryl Trithioarsenites, (ArS)3As,with Octasulfur

para‐Substituted with electron donating or electron withdrawing groups triphenyl trithioarsenites, (ArS)₃As, and octasulfur in refluxing carbon disulfide or chloroform do not give the triaryl tetrathioarsenates, (ArS)₃As=S, as was claimed in the literature for tris(4‐methylphenyl) tetrathioarsenate. In some cases oxidative decomposition to As₂O₃ and disulfides ArSSAr was found. When equivalent amounts of the same esters and octasulfur were heated at 105 or 150 °C no As^V compound was detected or isolated and again some esters decomposed to As₂O₃ and disulfides. These experiments demonstrated that the aromatic trithioarsenites do not react with octasulfur, probably because they cannot open the octasulfur ring. These esters in solution react with octasulfur in the presence of a catalytic (10—20 mol%) amount of triethylamine giving disulfides, As₂O₃ and colored solids which could not be characterized.     

Solubility and Raman Spectroscopic Study of As(III) Speciation in Organic Compound-Water Solutions. A Hydration Approach for Aqueous Arsenic in Complex Solutions

Solubilities of arsenolite (As₂O₃, cub.) were measured from 22 to 90°C in water–acetone, water–acetic acid, and water—formic acid solutions of compositions ranging from the pure organic compound to pure water. Raman spectra were obtained at ambient temperature on As-containing water–acetic acid and water–acetone solutions. Results show that arsenic solvation by these organic compounds is negligible and hydroxide species dominate As speciation over a wide range of water activity (a_{H 2 O}> 0.01). The solubility data were analyzed using an approach based on stoichiometric hydration reactions. Results show that As₂O₃ solubility can be described as a function of water activity, independently of the nature of the organic compound, by involving two neutral As hydroxide complexes: As(OH)₃ and As(OH)₃·4H₂O. Stability constants derived for these species indicate that hydration weakens with increasing temperature. Calculations using these constants show that at low temperatures the tetrahydrate As(OH)₃·4H₂O is dominant in water-rich solutions; by contrast, in high-temperature crustal fluids, As(OH)₃ becomes the major As species. The proposed hydration model can be used to analyze solubility of arsenic-bearing minerals and arsenic transport in complex H₂O–CO₂—electrolyte solutions encountered in natural and industrial environments.     

Die Chlorooxoarsenate(III) (PPh4)2[As4O2Cl10] · 2 CH3CN und (PPh4)2[As2OCl6] · 3 CH3CN

The Chlorooxoarsenates(III) (PPh₄)₂[As₄O₂Cl₁₀] · 2 CH₃CN and (PPh₄)₂[As₂OCl₆] · 3 CH₃CN (PPh₄)₂[As₂Cl₈] can be prepared from As₂O₃, SOCl₂ and PPh₄Cl in acetonitrile. Its oxidation with chlorine yields PPh₄[AsCl₆]. This was also obtained directly from arsenic, chlorine and PPh₄Cl, (PPh₄)₂[As₄O₂Cl₁₀] · 2 CH₃CN being a side product; the latter was obtained with high yield from AsCl₃, As₂O₃ and PPh₄Cl in acetonitrile. By addition of PPh₄Cl it was converted to (PPh₄)₂[As₂OCl₆] · 3 CH₃CN. According to their X-ray crystal structure analyses, both crystallize in the triclinic space group P 1. The [As₄O₂Cl₁₀]^2– ion can be regarded as a centrosymmetric association product of two Cl₂AsOAsCl₂ molecules and two Cl^– ions, each Cl^– ion being coordinated with all four As atoms. In the [As₂OCl₆]^2– ion the As atoms are linked via the O atom and two Cl atoms.     

Two New Polyoxovanadate‐supported Transition Metal Complexes: [Zn(en)2][Zn(en)2(H2O)2][{Zn(en)(enMe)}As6V15O42(H2O)]·4H2O and [Zn2(enMe)2(en)3][{Zn(enMe)2}As6V15O42(H2O)]·4H2O

Two novel As‐V‐O cluster supported transition metal complexes, [Zn(en)₂][Zn(en)₂(H₂O)₂][{Zn(en)(enMe)}As₆V₁₅O₄₂(H₂O)]·4H₂O ( 1 ) and [Zn₂(enMe)₂(en)₃][{Zn(enMe)₂}As₆V₁₅O₄₂(H₂O)]·4H₂O ( 2 ), have been hydrothermally synthesized. The single X‐ray diffraction studies reveal that both compounds consist of discrete noncentral polyoxoanions [{Zn(en)(enMe)}As₆V₁₅O₄₂(H₂O)]^4? or [{Zn(enMe)₂}As₆V₁₅O₄₂(H₂O)]^4? cocrystallized with respective zinc coordination complexes. Interestingly, compounds 1 and 2 exhibit the first two polyoxovanadates containing As₈V₁₅O₄₂‐(H₂O)]^6? cluster decorated by only one transition metal complex. Crystal data: 1 , monoclinic, P2₁/n, a = 14.9037(4) Å, b = 18.1243(5) Å, c = 27.6103(7) Å, β = 105.376(6)°, Z = 4; 2 monoclinic, P2₁/n, a = 14.9786(7) Å, b = 33.0534(16) Å, c = 14.9811(5) Å, Z = 4.     

Organoantimony(III)‐Containing Tungstoarsenates(III): From Controlled Assembly to Biological Activity

A family of three sandwich‐type, phenylantimony(III)‐containing tungstoarsenates(III), [(PhSb^III){Na(H₂O)}As^III₂W₁₉O₆₇(H₂O)]^11? ( 1 ), [(PhSb^III)₂As^III₂W₁₉O₆₇(H₂O)]^10? ( 2 ), and [(PhSb^III)₃(B‐α‐As^IIIW₉O₃₃)₂]^12? ( 3 ), have been synthesized by one‐pot procedures and isolated as hydrated alkali metal salts, Cs₃K_3.5Na_4.5[(PhSb^III){Na(H₂O)}As^III₂W₁₉O₆₇(H₂O)]?41H₂O ( CsKNa ‐ 1 ), Cs_4.5K_5.5[(PhSb^III)₂As^III₂W₁₉O₆₇(H₂O)]?35H₂O ( CsK‐2 ), and Cs_4.5Na_7.5[(PhSb^III)₃(B‐α‐As^IIIW₉O₃₃)₂]?42H₂O ( CsNa ‐ 3 ). The number of incorporated {PhSb^III} units could be selectively tuned from one to three by careful control of the reaction parameters. The three compounds were characterized in the solid state by single‐crystal XRD, IR spectroscopy, and thermogravimetric analysis. The aqueous solution stability of sandwich polyanions 1 – 3 was also studied by multinuclear (¹H, ¹³C, ¹⁸³W) NMR spectroscopy. Effective inhibitory activity against six different kinds of bacteria was identified for all three polyanions, for which the activity increased with the number of incorporated {PhSb^III} groups.     

Effect of the Media on the Quantum Yield of Singlet Oxygen (O2(1Δg)) Production by 9H‐Fluoren‐9‐one: Solvents and Solvent Mixtures

We have investigated the effect of a series of 18 solvents and mixtures of solvents on the production of singlet molecular oxygen (O₂(¹Δ_g), denoted as ¹O₂) by 9H‐fluoren‐9‐one (FLU). The normalized empirical parameter E derived from E_T(30) has been chosen as a measure of solvent polarity using Reichardt's betaine dyes. Quantum yields of ¹O₂ production (Φ_Δ) decrease with increasing solvent polarity and protic character as a consequence of the decrease of the quantum yield of intersystem crossing (Φ_ISC). Values of Φ_Δ of unity have been found in alkanes. In nonprotic solvents of increasing polarity, Φ_ISC and, therefore, Φ_Δ decrease due to solvent‐induced changes in the energy levels of singlet and triplet excited states of FLU. This compound is a poor ¹O₂ sensitizer in protic solvents, because hydrogen bonding considerably increases the rate of internal conversion from the singlet excited state, thus diminishing Φ_Δ to values much lower than those in nonprotic solvents of similar polarity. In mixtures of cyclohexane and alcohols, preferential solvation of FLU by the protic solvent leads to a fast decrease of Φ_Δ upon addition of increasing amounts of the latter.     

[Ho5(H2O)16(OH)2As6W64O220]25−, ein großes neuartiges Polyoxoanion aus trivakanten Keggin‐Fragmenten

[Ho₅(H₂O)₁₆(OH)₂As₆W₆₄O₂₂₀]^25?, a Large Novel Polyoxoanion from Trivacant Keggin Fragments The novel polyoxotungstate Na₇K₁₈[Ho₅(H₂O)₁₆(OH)₂As₆W₆₄O₂₂₀] · 56 H₂O ( 1 ) was synthesized in aqueous solution and characterized by X‐ray structure analysis, elemental analysis and IR spectroscopy. The anion in 1 represents one of the largest polyoxoanions known yet and exhibits an unusual arrangement of six Keggin units. It consists of six trivacant lacunary α‐B‐(AsW₉O₃₃)^9? Keggin fragments which are connected by a bridging [Ho₅W₁₀(H₂O)₁₆(OH)₂O₂₂]²⁹⁺ unit. The five Ho^III atoms are coordinated by eight oxygen atoms, forming a square‐antiprism.     

Sm2As4O9: Ein ungewöhnliches Samarium(III)‐Oxoarsenat(III) gemäß Sm4[As2O5]2[As4O8]

Sm₂As₄O₉: An Unusual Samarium(III) Oxoarsenate(III) According to Sm₄[As₂O₅]₂[As₄O₈] Pale yellow single crystals of the new samarium(III) oxoarsenate(III) with the composition Sm₄As₈O₁₈ were obtained by a typical solid‐state reaction between Sm₂O₃ and As₂O₃ using CsCl and SmCl₃ as fluxing agents. The compound crystallizes in the triclinic crystal system with the space group (No. 2, Z = 2; a = 681.12(5), b = 757.59(6), c = 953.97(8) pm, α = 96.623(7), β = 103.751(7), γ = 104.400(7)°). The crystal structure of samarium(III) oxoarsenate(III) with the formula type Sm₄[As₂O₅]₂[As₄O₈] (≡ 2 × Sm₂As₄O₉) contains two crystallographically different Sm³⁺ cations, where (Sm1)³⁺ is coordinated by eight, but (Sm2)³⁺ by nine oxygen atoms. Two different discrete oxoarsenate(III) anions are present in the crystal structure, namely [As₂O₅]^4? and [As₄O₈]^4?. The [As₂O₅]^4? anion is built up of two Ψ¹‐tetrahedra [AsO₃]^3? with a common corner, whereas the [As₄O₈]^4? anion consists of four Ψ¹‐tetrahedra with ring‐shaped vertex‐connected [AsO₃]^3? pyramids. Thus at all four crystallographically different As³⁺ cations stereochemically active non‐binding electron pairs (“lone pairs”) are observed. These “lone pairs” direct towards the center of empty channels running parallel to [010] in the overall structure, where these “empty channels” being formed by the linkage of layers with the ecliptically conformed [As₂O₅]^4? anions and the stair‐like shaped [As₄O₈]^4? rings via common oxygen atoms (O1 – O6, O8 and O9). The oxygen‐atom type O7, however, belongs only to the cyclo‐[As₄O₈]^4? unit as one of the two different corner‐sharing oxygen atoms.     

Ein Metaarsenat(V) Anion neuartiger Konstitution in AgAsO3

Metaarsenate(V) Anion of Novel Constitution in AgAsO₃ AgAsO₃ was prepared, for the first time, through solid state reaction of Ag₂O and As₂O₃, or As, respectively, while applying an elevated oxygen pressure (T = 500 °C, p(O₂) = 2 kbar, 1—2 days). The crystal structure (Pca2₁; a = 1948.8(3), b = 660.0(1), c = 1266.1(3) pm; Z = 24; 4741 independent reflexions; R₁ = 0.044) contains a novel polyanion, equation/tex2gif-stack-2.gif[(AsO_6/2)(AsO_2/1O_2/2)₂], with arsenic in an octahedral and tetrahedral coordination, at the same time. It thus features structural units similar to those in binary As₂O₅.     

Loss of activity by vanadium sulfuric acid catalysts under the action of arsenic(III) oxide vapor

Chemical processes leading to inactivation of vanadium sulfuric acid catalysts by arsenic(III) oxide vapor were studied. The interaction and solubility in the system VO(H₂AsO₄)₂-VOAsO₄-H₃AsO₄-H₂O and the composition of oxovanadium arsenate in a mixed oxidation state, used as a starting substance in synthesis of (V^IVO)(V^VO)₂(As₂O₇)₂, were examined.     

A Ferromagnetically Coupled (S=1) Peroxodicopper(II) Complex

Copper enzymes play important roles in the binding and activation of dioxygen in biological systems. Key copper/dioxygen intermediates have been identified and studied in synthetic analogues of the metalloprotein active sites, including the μ‐η²:η²‐peroxodicopper(II) motif relevant to type III dicopper proteins. Herein, we report the synthesis and characterization of a bioinspired dicopper system that forms a stable μ‐η¹:η¹‐peroxo complex whose Cu‐O‐O‐Cu torsion is constrained to around 90° by ligand design. This results in sizeable ferromagnetic coupling between the copper(II) ions, which is detected by magnetic measurements and HF‐EPR spectroscopy. The new dicopper peroxo system is the first with a triplet ground state, and it represents a snapshot of the initial stages of O₂ binding at type III dicopper sites.     

[As(V)As(III)O6]: An uncommon anion group in the crystal structure of K2Cu3(As2O6)2

The crystal structure of K₂Cu₃(As₂O₆)₂ was determined from single-crystal X-ray data by a direct method strategy and Fourier summations [a = 10.359(4) Å, B = 5.388(2)Å, C = 11.234(4) Å, β = 110.48(2)°; space group C2/m; Z = 2; R_w = 0.025 for 1199 reflections up to sin /λ = 0.81 Å⁻¹]. In detail, the structure consists of As(V)O₄ tetrahedra and As(III)O₃ pyramids linked by a common O corner atom to [As(V)As(III)O₆]⁴⁻ groups with symmetry m. The bridging bonds As(V)---O [1.749(3) Å] and As(III)---O [1.838(2) Å] are definitely longer than the other As(V)---O bonds [mean 1.669 Å] and As(III)---O bonds [1.764(2) Å, 2×]. The angle As(V)---O---As(III) is 123.0(1)°. The Cu atoms are [4 + 2]- and [4 + 1]-, and the K atom is [9]-coordinated to oxygen atoms. The As₂O₆ groups and the Cu coordination polyhedra are linked to sheets parallel to (001). These sheets are connected by the K atoms. Single crystals of K₂Cu₃(As₂O₆)₂ suitable for X-ray work were synthesized under hydrothermal conditions.     

Synthesis and Structural Chemistry of Tungstoarsenates(V)

An overview of the synthesis and of the structural chemistry of tungstoarsenates(V) of the 1:12 and 2:21 families is presented with special emphasis on the 2:20 species. The molecular structure of [As₂W₂₀O₇₁(H₂O)₃]¹²⁻ has been determined by single-crystal X-ray diffraction of K₁₂[As₂W₂₀O₇₁(H₂O)₃]·23H₂O and that of [As₂W₂₀O₇₀(H₂O)₂]¹⁰⁻ has been inferred from a ¹⁸³W NMR study in aqueous solution.This paper is dedicated to Professor Michael Pope in recognition of his invaluable contribution to polyoxometalate chemistry.     

The influence of P/As substitution in the melilite‐like Na2Co(P2–xAsx)O7 (x = 0.40 and 0.93) solid solutions

To investigate the influence of P/As substitution on structures and electrical properties, e.g. the effect on material densities, two new solid P/As‐doped solutions, Na₂CoP_1.60As_0.40O₇ (disodium cobalt diphosphorus arsenic heptaoxide) and Na₂CoP_1.07As_0.93O₇ (disodium cobalt phosphorus arsenic heptaoxide), with melilite‐like structures have been synthesized by solid‐state reactions. Their unit‐cell parameters are in agreement with Vegard's law. The obtained structural models were investigated by the bond valence sum (BVS) and charge distribution (CHARDI) validation tools and, for the latter, the structures are described as being built on anion‐centred polyhedra. The frameworks can be described as layered and formed by {[Co(P,As)₂O₇]²⁻}_∞ slabs, with alkali cations sandwiched between the layers and with the interlayer spaces increased due to P/As substitution. The BVS model was extended to a preliminary simulation of the sodium conduction properties in the studied structural type and suggests that the most probable sodium conduction pathways are bidimensional, at the (002) planes.     

Oxidopolyborate chemistry: The self-assembled,templated, synthesis,and an XRD study of a 1-D coordination polymer, [Cu(en){B6O7(OH)6}].3H2O (en = 1,2-diaminoethane)

Abstract

[Cu(en){B₆O₇(OH)₆}]^.3H₂O (1) (en = 1,2-diaminoethane), obtained as a crystalline solid in low yield (31%) after prolonged standing of an aqueous solution initially containing [Cu(en)₂](OH)₂ and B(OH)₃ (1:7 ratio), was characterized by thermal analysis (TGA/DSC), ¹¹B NMR and IR spectroscopy, powder XRD, and single-crystal XRD studies, and magnetic susceptibility measurements. The single-crystal X-ray diffraction revealed that the oxidoborate complex is a 1D coordination polymer with the hexaborate(2-) ligand bridging two hexacoordinate Cu^(II) centers, in an alternating a fac-tridentate (κ³-O) and monodentate (κ¹-O) arrangement. Cu-O coordination bonds and extensive H-bonding networks promote and stabilize the self-assembly of [Cu(en){B₆O₇(OH)₆}]^.3H₂O from the Dynamic Combinatorial Libraries of available reactants. [Cu(en){B₆O₇(OH)₆}]^.3H₂O is thermally decomposed to CuB₆O₁₀ in air at 700?°C.     

Intake of different chemical species of dietary arsenic by the japanese,and their blood and urinary arsenic levels

We calculated the intake of each chemical species of dietary arsenic by typical Japanese, and determined urinary and blood levels of each chemical species of arsenic. The mean total arsenic intake by 35 volunteers was 195±235 (15.8-1039) μg As day^?1, composed of 76% trimethylated arsenic (TMA), 17.3% inorganic arsenic (As_i), 5.8% dimethylated arsenic (DMA), and 0.8% monomethylated arsenic (MA): the intake of TMA was the largest of all the measured species. Intake of As_i characteristically and invariably occurred in each meal. Of the intake of As_i, 45-75% was methylated in vivo to form MA and DMA, and excreted in these forms into urine. The mean measured urinary total arsenic level in 56 healthy volunteers was 129±92.0 μg As dm^?3, composed of 64.6% TMA, 26.7% DMA, 6.7% As_i and 2.2% MA. The mean blood total arsenic level in the 56 volunteers was 0.73±0.57 μg dl^?1, composed of 73% TMA, 14% DMA and 9.6% As_i. The urinary TMA levels proved to be significantly correlated with the whole-blood TMA levels (r = 0.376; P<0.01).     

Cerium(IV) Hexanuclear Clusters from Cerium(III) Precursors: Molecular Models for Oxidative Growth of Ceria Nanoparticles

Reactions of cerium(III) nitrate, Ce(NO₃)₃?6 H₂O, with different carboxylic acids, such as pivalic acid, benzoic acid, and 4‐methoxybenzoic acid, in the presence of a tridentate N,N,N‐donor ligand, diethylenetriamine (L¹), under aerobic conditions yielded the corresponding cerium hexamers Ce₆O₈(O₂CtBu)₈(L¹)₄ ( 1 ), Ce₆O₈(O₂CC₆H₅)₈(L¹)₄ ( 2 ), and Ce₆O₈(O₂CC₆H₄‐4‐OCH₃)₈(L¹)₄ ( 3 ). Hexamers 1 , 2 , and 3 contain the same octahedral Ce^IV₆O₈ core, in which all interstitial oxygen atoms are connected by μ₃‐oxo bridging ligands. In contrast, treatment of the Ce^IV precursor (NH₄)₂Ce(NO₃)₆ (CAN) with pivalic acid and the ligand L¹ under the same conditions afforded Ce₆O₄(OH)₄(O₂CtBu)₁₂(L¹)₂ ( 4 ), exhibiting a deformed octahedral Ce^IV₆O₄(OH)₄ core containing μ₃‐oxo and μ₃‐hydroxo moieties in defined positions. In contrast to the formation of 1 – 3 , the use of N‐methyldiethanolamine (L) in the reaction with Ce(NO₃)₃?6 H₂O and pivalic acid afforded a previously reported Ce^III dinuclear cluster, Ce₂(O₂CtBu)₆L₂, even in the presence of dioxygen. ESI‐MS analysis of the reaction mixture clearly indicated the importance of the ligand L¹ in promoting oxidation of the Ce^III aggregates, [Ce_n(O₂CtBu)_3n(L¹)₂], which is necessary for the formation of Ce^IV hexamers.     

Co(en)3[B4O5(OH)4]Cl·3H2O和[Ni(en)3][B5O6(OH)4]2·2H2O的合成、结构以及热力学性质

利用水热法合成了两种过渡金属配合物为模板剂的含水硼酸盐晶体Co(en)3[B4O5(OH)4]Cl·3H2O(1) 和 [Ni(en)3][B5O6(OH)4]2·2H2O (2),并通过元素分析、X射线单晶衍射、红外光谱及热重分析对其进行了表征。化合物1晶体结构的主要特点是在所有组成Co(en)33+, [B4O5(OH)4]2–, Cl– 和 H2O之间通过O–H…O、O–H…Cl、N–H…Cl和N–H…O四种氢键连接形成网状超分子结构。化合物2晶体结构的特点是[B5O6(OH)4]–阴离子通过O–H…O氢键连接形成沿a方向有较大通道的三维超分子骨架,模板剂[Ni(en)3]2+阳离子和结晶水分子填充在通道中。     

Thermal behaviour of arsenic oxides (As2O5 and As2O3) and the influence of reducing agents (glucose and activated carbon)

In this paper the thermal behaviour of pure arsenic oxides (As₂O₅.aq and As₂O₃) and the influence of the presence of reducing agents (glucose or activated carbon) on the thermal behaviour of the arsenic oxides are studied through thermogravimetric (TG) analysis.The TG experiments with pure As₂O₅.aq reveal that the reduction reaction As₂O₅→As₂O₃+O₂ does not take place at temperatures lower than 500 °C. At higher temperatures decomposition is observed. Pure As₂O₃, however, is already released at temperatures as low as 200 °C. This release is driven by temperature dependent vapour pressures.Comparing these results with earlier observations concerning the thermal behaviour of chromated copper arsenate (CCA) treated wood, suggests that wood, char and pyrolysis vapours form a reducing environment that influences the thermal behaviour of arsenic oxides. Therefore, the influence of the presence of reducing agents on the thermal behaviour of As₂O₅.aq is studied. First, TG experiments are carried out with mixtures of As₂O₅ and glucose. The TG and DTG curves of the mixture are not a simple superposition of the curves of the two pure constituents. The interaction between As₂O₅.aq and glucose results in a faster decomposition of arsenic pentoxide. This effect is more pronounced if the purge gas nitrogen is mixed with oxygen. Second, TG experiments are performed with mixtures of As₂O₅ and activated carbon. The presence of activated carbon also promotes the volatilisation of arsenic for temperatures higher than 300 °C, probably through its reducing action.Extrapolation of the thermal behaviour of these model compounds to the real situation of pyrolysis of CCA treated wood confirms the statement that the reduction of pentavalent arsenic to trivalent arsenic is favoured by the reducing environment, created by the presence of wood, char and pyrolysis vapours.