Reactivity of Ammonium Halides: Action of Ammonium Chloride and Bromide on Iron and Iron(III) Chloride and Bromide

Ammonium chloride and bromide, (NH₄)Cl and (NH₄)Br, act on elemental iron producing divalent iron in [Fe(NH₃)₂]Cl₂ and [Fe(NH₃)₂]Br₂, respectively, as single crystals at temperatures around 450 °C. Iron(III) chloride and bromide, FeCl₃ and FeBr₃, react with (NH₄)Cl and (NH₄)Br producing the erythrosiderites (NH₄)₂[Fe(NH₃)Cl₅] and (NH₄)₂[Fe(NH₃)Br₅], respectively, at fairly low temperatures (350 °C). At higher temperatures, 400 °C, iron(III) in (NH₄)₂[Fe(NH₃)Cl₅] is reduced to iron(II) forming (NH₄)FeCl₃ and, further, [Fe(NH₃)₂]Cl₂ in an ammonia atmosphere. The reaction (NH₄)Br + Fe (4:1) leads at 500 °C to the unexpected hitherto unknown [Fe(NH₃)₆]₃[Fe₈Br₁₄], a mixed‐valent Fe^II/Fe^I compound. Thermal analysis under ammonia and the conditions of DTA/TG and powder X‐ray diffractometry shows that, for example, FeCl₂ reacts with ammonia yielding in a strongly exothermic reaction [Fe(NH₃)₆]Cl₂ that at higher temperatures produces [Fe(NH₃)]Cl₂, FeCl₂ and, finally, Fe₃N.     

Heteronuclear compounds formed in the systems based on Fe(II), Fe(III), Al(III), SO 42? , Cl?-H2O-OH?, and NH3

The possibility of synthesizing heteronuclear compounds in the systems based on Fe(II), Fe(III), Al(III), SO₄²⁻, Cl⁻-H₂O-OH⁻, and NH₃ was studied. A mathematical model based on data on the potentiometric titration was developed. The elemental and phase composition and the structure of the compounds synthesized were determined by the XPA, DTA and NMR methods to optimize the conditions of the synthesis.     

Thermal decomposition of the [Co(NH3)6]Cl3, Co[(NH3)4Cl2]Cl,K3[Fe(C2O4)3]3H2O and Fe(CH3COO)3 in argon and air atmosphere

Kinetic parameters (apparent activation energy, reaction order, pre-exponential factor (Z) in the Arrhenius equation) for thermal decomposition of the [Co(NH₃)₆]Cl₃, Co[(NH₃)₄Cl₂]Cl, K₃[Fe(C₂O₄)₃]3H₂O and Fe(CH₃COO)₃ are reported. They have been calculated on the DTA and TG data according to Coats-Redfern's model. Both, decomposition data obtained in argon and in air atmosphere have been considered and the results are compared.

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Zusammenfassung Es werden die kinetischen Parameter (scheinbare Aktivierungsenergie, Reaktionsordnung, prÄexponentieller Faktor (Z) der Arrhenius-Gleichung) der thermischen Zersetzung von [Co(NH₃)₆]Cl₃, [Co(NH₃)₄Cl₂]Cl, K₃[Fe(C₂O₄)₃]3H₂O und Fe(CH₃COO)₃ beschrieben, die entsprechend dem Coats-Redfern-Modell auf der Basis der DTA- und TG-Daten errechnet wurden. Die Zersetzung wurde sowohl in Argon als auch in Luft durchgeführt und die erhaltenen Daten miteinander verglichen.

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Helpful comments from Professor W. Wojciechowski and financial support from Institute for Low Temperatures and Structure Research Polish Academy of Sciences (CPBP 01.12) are greatefully acknowledged.     

Iron(III) hetero-ligand complexes containing 1,10-phenanthroline derivatives, chloride and dimethyl sulfoxide: synthesis, characterization, crystal structure determination and luminescent properties

[Fe(Me-phen)Cl₄][Me-phen·H] (1) and [Fe(Cl-phen)Cl₄][Cl-phen·H] (2) complexes were prepared from the reactions of FeCl₃·6H₂O with 5-methyl-1,10-phenanthroline (Me-phen) and 5-chloro-1,10-phenanthroline (Cl-phen), respectively, in a 0.1 M aqueous solution of HCl. Stepwise addition of dimethyl sulfoxide to the solution of 1 in methanol results in a mixed ligand complex, [Fe(Me-phen)Cl₃(DMSO)] (3). Complex 3 was also prepared by two other methods. The reaction of a methanol solution of [Fe(Me-phen)Cl₄][Me-phen·H] (1) with [Fe(DMSO)₄Cl₂][FeCl₄] in 1:6 ratio led to 3. Complex 3 was also prepared from the reaction of 5-methyl-1,10-phenanthroline with [Fe(DMSO)₄Cl₂][FeCl₄] in 1:1 ratio in methanol. The three complexes were characterized by IR, UV–Vis, ¹H NMR and luminescence spectroscopy and their structures were studied by the single-crystal diffraction method. Calculation methods were employed to study the isomerization of (3) in solution.     

Thermoanalytical investigations of 4-methylpiperazine-1-carbodithioic acid ligand and its iron(III), cobalt(II), copper(II) and zinc(II) complexes

The thermal decomposition studies on 4-methylpiperazine-1-carbodithioic acid ligand (4-MPipzcdtH) and its complexes, viz. [M(4-MPipzcdtH)_n](ClO4)_n (M=Fe(III) when n=3; M=Co(II), Cu(II) when n=2) and [Zn(4-MPipzcdtH)₂]Cl₂ have been carried out using non-isothermal techniques (TG and DTA). Initial decomposition temperatures (IDT), indicate that thermal stability is influenced by the change of central metal ion. Free acid ligand exhibits single stage decomposition with a sharp DTA endotherm. Complexes, [M(4-MPipzcdtH)_n](ClO₄)_n undergo single stage decomposition with detonation and give rise to very sharp exothermic DTA curves while the complex [Zn(4-MPipzcdtH)₂]Cl₂ shows three-stage decomposition patterns. The kinetic and thermodynamic parameters, viz. the energy of activation E, the frequency factor A, entropy of activation S and specific rate constant k, etc. have been evaluated from TG data using Coats and Redfern equation. Based upon the results of the differential thermal analysis study, the [M(4-MPipzcdtH)_n](ClO₄)_n complexes have been found to possess characteristic of high energy materials.     

Thermal Analysis of Hexachloroplumbate and Chlorides Containing Complex Divalent Lead 2,2'-bipyridine Cations

Lead(II) 2,2'-bipyridine hexachloroplumba tetetrahydrate was synthesized and investigated by DTA, TG and DTG. IR spectroscopy and other methods enabled the identification of some of the decomposition products. Comparative studies on the corresponding chlorides: [Pb(bipy)]Cl₂ and [Pb(bipy)₃]Cl₂, which can be considered as precursors of the hexachloroplumbate, were also undertaken. X-ray measurements enabled the tentative determination of the crystal structure of [Pb(bipy)]Cl₂. Hexachloroplumbate decomposes with the liberation of chlorine, water and organic ligands, and the process is accompanied by the simultaneous transition of Pb(IV)→Pb(II). Chlorides release only ligands upon heating. Residues comprised always PbCl₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthese und Strukturaufklärung von neuen (Eisencarbonyl)zinkund ‐cadmiumchlorid‐Derivaten

Syntheses and Structure Elucidations of Novel (Ironcarbonyl)zinc and ‐cadmium Chloride Derivatives Reactions of zinc/cadmium chloride with Na₂[Fe(CO)₄] lead to a number of new (iron carbonyl)zinc/cadmium chlorides, wherein the reaction course depends on the used solvent used. In the reaction of ZnCl₂ with Na₂[Fe(CO)₄], three new substances can be prepared. The compound [Zn₂Cl₂Fe(CO)₄(THF)₂] ( 1 ), which consists of neutral polymeres, is formed in THF, the ionic compound [Na(DME)₃][Zn₂Cl₃Fe(CO)₄] ( 2 ) forms in DME, and from a mixture of THF and TMEDA the compound [Zn₂Cl₂Fe(CO)₄(TMEDA)₂] ( 3 ) is obtained as a monomere. Also by using CdCl₂, the reaction with Na₂[Fe(CO)₄] in THF leads to the polymeric compound ([(Cd₄Cl₆)Fe(CO)₄(THF)₅] ( 4 )). Carrying out the reaction in a mixture of toluene and DME leads to the formation of the ionic compound [Na(DME)₃]₂[Cd₆{Fe(CO)₄}₆Cl₂(DME)₂] ( 5 ) in which an annular dianion consisting of twelve metal atoms is found. From an aqueous solution and subsequent work‐up in THF, the compound [Fe(THF)₄(H₂O)₂][Cd₈{Fe(CO)₄}₄Cl₉(THF)₆]₂ ( 6 ) can be prepared which contains an cluster anion that is built of anellated six membered rings.     

Catalytic Applications of Nano‐Fe‐[Phenyl‐Salicylaldimine‐Methylpyranopyrazole]Cl2 as a Schiff Base Complex and Nanostructured Catalyst for the Synthesis of Hexahydroquinolines

By the four‐component condensation reaction of benzaldehyde with ethyl acetoacetate, malononitrile, and hydrazine hydrate using FeCl₂, a pyranopyrazole derivative was synthesized and then reacted with salicylaldehyde to give nano‐Fe‐[phenyl‐salicylaldimine‐methylpyranopyrazole]Cl₂ (nano‐[Fe‐PSMP]Cl₂). The prepared nano‐Schiff base complex was successfully used as an efficient catalyst for the synthesis of hexahydroquinolines.     

Preparation and spectroscopic characterization of iron(II) and copper(II) complexes of a functionalized crown ether

Condensation between 4′-aminobenzo-15-crown-5- and 4-antipyrinecarboxaldehyde yielded the functionalized crown ether (L = 1,5-dimethyl-4-[(2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecin-15-ylimino)methyl]-2-phenyl-1,2-dihydro-3H-pyrazol-3-one). A 1:1 (Na⁺:L) complex has been prepared. The reaction of Fe(II) and Cu(II) salts with L gave complexes of composition [Fe(L)Cl₂] and [Cu(L)₂Cl₂]. Heteronuclear complexes [Fe(L)Cl₂Na]ClO₄ and [Cu(L)₂Cl₂Na]ClO₄ have also been synthesized from the reactions of [Fe(L)Cl₂] and [Cu(L)₂Cl₂] with NaClO₄. The compounds have been characterized by microanalyses and spectroscopic methods.     

The Peltier heat and the standard electrode potential of ferro-ferricyanide couple at 298.15 K determined by electrochemical–calorimetry

An experiment was done on electrochemical–calorimetry to identify the Peltier heats of the ferro-ferricyanide reversible electrode reaction over the concentration range of 0.075–0.3 mol dm⁻³ at 298.15 K. A new approach has been developed to obtain the standard potential of this electrode, which was identified as (+0.3580 ± 0.0030) volt at 298.15 K and compared with previously reported values. An equation derived from the approach is also applied to several standard couples, such as Fe(CN)₆⁻³/Fe(CN)₆⁻⁴, H⁺/H₂, Cu²⁺/Cu, Cl⁻/Hg₂Cl₂,Hg, Fe³⁺/Fe²⁺, and Cl⁻/Cl₂ to determine their respective reaction heats with satisfying results.     

Influence of arsenate species on the formation of Fe(III) oxyhydroxides and Fe(II–III) hydroxychloride

Iron(III) oxyhydroxides were prepared by oxidation of aerated aqueous suspensions of Fe(II) hydroxide. The effects of arsenate species on their formation were studied by mixing FeCl₂·4H₂O, NaOH and Na₂HAsO₄ solutions. The intermediate and final products of the oxidation processes were characterised by X-ray diffraction, Infrared and Raman spectroscopy. Arsenate species were not reduced during the process but they influenced both oxidation stages, that is the formation of the intermediate Fe(II–III) compound and its subsequent oxidation into Fe(III) compounds. Arsenate species clearly inhibited the growth and hindered the crystallisation of GR(Cl^?), the Fe(II–III) hydroxychloride that would have formed in the experimental conditions considered here. For the largest arsenate concentrations, the intermediate product was nanocrystalline and more likely consisted of clusters showing an ordering of atoms similar to that of GR(Cl^?), isolated from each other by adsorbed arsenate species. The adsorption of As(V) prevented growth of these clusters into well-crystallised GR(Cl^?). The arsenate species influenced similarly the second reaction stage by inhibiting the formation of well-ordered and crystallised Fe(III) compounds. Lepidocrocite, the final product in the absence of arsenate, was replaced by “6-line” ferrihydrite with increasing As(V) concentration, then “6-line” ferrihydrite was replaced by another poorly ordered compound, feroxyhite. These crystallised compounds were obtained together with an increasing part of nanocrystalline Fe(III) ox(yhydrox)ide(s).     

Synthesis of pyranopyrazoles using nano‐Fe‐[phenylsalicylaldiminemethylpyranopyrazole]Cl2 as a new Schiff base complex and catalyst

By the condensation reaction of benzaldehyde with ethyl acetoacetate, malononitrile and hydrazine hydrate in the presence of FeCl₂, a pyranopyrazole derivative was prepared which was then reacted with salicylaldehyde to afford nano‐Fe‐[phenylsalicylaldiminemethylpyranopyrazole]Cl₂ (nano‐[Fe‐PSMP]Cl₂). The prepared nano‐Schiff base complex was fully characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, differential thermogravimetry, scanning electron microscopy and UV–visible spectroscopy, and was used as an efficient and catalyst for the preparation of pyranopyrazoles.     

Synthesis and characterization of nanocrystalline α-Al2O3 using Al and Fe2O3 (hematite) through mechanical alloying

In this present work, the synthesis of nanocrystalline α-Al₂O₃ using pure aluminum (Al) and Fe₂O₃ (hematite) as the precursors by mechanical alloying technique has been studied. The formation of α-Al₂O₃ nanocrystallites occurs during the solid-state reaction and through the reduction treatment. Also in this paper, effects of milling time on particle size and the lattice strain nanocrystalline α-Al₂O₃ have been investigated. Obtained powders were evaluated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential thermal analysis (DTA), thermal gravimetric analysis (TGA) and X-ray diffraction (XRD). The obtained results indicated that a reduction reaction was completed after 2 h milling in a planetary mill. The crystallite size of obtained α-alumina (α-Al₂O₃) was in general about 12 nm. Finally, the results showed appropriate homogeneity and dispersion of related nanocrystalline.     

TIN AND GERMANIUM COMPLEXES WITH MALTOL

Abstract

The reaction of tin and germanium tetrachlorides with 3-hydroxy-2-methyl-4H-pyran-4-one (HMa) in benzene yielded M(HMa)₄Cl₄·C₆H₆ (M = Sn or Ge) adducts, whereas in methanol the MMa₂Cl₂ complexes have been isolated. Moreover, tin complexes with the neutral donors 2,6-dimethyl-4H-pyran-4-one (DMP) and 2,6-dimethyl-4H-pyran-4-thione (DMTP), having formulae Sn(L)₂Cl₂ and Sn(L)₂Cl₄(L = DMP or DMTP) have been prepared. The compounds have been characterized by ir and proton nmr spectroscopy and by thermogravimetric (TG and DTA) analysis. The thermal behaviour of all complexes has been followed to 1200°C. The stability of the M(HMa)₄Cl₄ adducts in various solvents is discussed on the basis of proton nmr spectra.     

Effect of chlorinating reagents on Zr recovery from Zircaloy-4 hull wastes: reaction behavior simulation by using the HSC code

Chlorination reaction behavior of Zircaloy-4 (Zry-4) was simulated by using the HSC code for three different chlorinating reagents of Cl₂, HCl, and CCl₄. Four major components (Zr, Sn, Fe, and Cr) of Zry-4 and their oxides which were produced during an oxidative decladding process were considered for the theoretical calculation. The simulation results revealed that Cl₂ might convert metallic Zr, Sn, Fe, and Cr into their chloride forms, while oxides might not react with Cl₂ at 380 °C. When HCl was employed as the chlorinating reagent, it was suggested that metallic Zr, Sn, and Cr might react with HCl while Fe and oxides might not. In the case of CCl₄, it was shown that CCl₄ could react with all of the metallic and oxide components to produce most amount of ZrCl₄ when compared with Cl₂ and HCl cases. Reaction behavior of the chlorinating reagents with residual spent nuclear fuel constituents (U₃O₈, MoO₃, Pd, BaO, Y₂O₃, SrO, Rh₂O₃, RhO₂, La₂O₃, CeO₂, and Nd₂O₃) was also performed, and it was revealed that Cl₂ and HCl might produce (PdCl₂, BaCl₂, SrCl₂, RhCl₃, LaCl₃, and NdCl₃) and (BaCl₂, YCl₃, SrCl₂, RhCl₃, LaCl₃, and NdCl₃), respectively. Although these by-products are produced, it was suggested that highly pure ZrCl₄(g) which contains FeCl₃(g) and SnCl₄(g) as impurities might be recovered when Cl₂ or HCl is employed as a chlorinating reagent because other by-products have higher boiling point than the reaction temperature of this study (380 °C). On the other hand, the theoretical calculation results showed that CCl₄ might react with all the residual spent fuel constituents to produce additional gaseous impurities of UCl₆ and MoCl₅ to reduce the purity of ZrCl₄ product.     

Synthesis,characterization and crystal structure determination of iron(III) complexes containing 4,4′-dimethyl-2,2′-bipyridine,dimethyl sulfoxide and chloride, [Fe(dmbipy)Cl4][dmbipyH] and [Fe(dmbipy)Cl3(DMSO)]

[Fe(dmbipy)Cl₄][dmbipyH], 1 (dmbipy is 4,4′-dimethyl-2,2′-bipyridine), was prepared from reaction of FeCl₃ · 6H₂O with 4,4′-dimethyl-2,2′-bipyridine in 0.1 molar aqueous HCl. Treatment of 1 with dimethyl sulfoxide in methanol produced [Fe(dmbipy)Cl₃(DMSO)], 2 (DMSO is dimethyl sulfoxide). Both complexes were characterized by IR, UV-vis, and ¹H-NMR spectroscopies and their structures were studied by single crystal diffraction. Compounds 1 and 2 are high-spin with spin multiplicity of six.     

Enhanced degradation of organic contaminants by Fe(III)/peroxymonosulfate process with l-cysteine

The difficulty in Fe(III)/Fe(II) conversion in the Fe(III)/peroxymonosulfate (PMS) process limits its efficiency and application. Herein, l-cysteine (Cys), a green natural organic ligand with reducing capability, was innovatively introduced into Fe(III)/PMS to construct an excellent Cys/Fe(III)/PMS process. The Cys/Fe(III)/PMS process, at room temperature, can degrade a variety of organic contaminants, including dyes, phenolic compounds, and pharmaceuticals. In subsequent experiments with acid orange 7 (AO7), the AO7 degradation efficiency followed pseudo-first-order kinetic which exhibited an initial “fast stage” and a second “slow stage”. The rate constant values ranged depending on the initial Cys, Fe(III), PMS, and AO7 concentrations, reaction temperature, and pH values. In addition, the presence of Cl^?, NO₃^?, and SO₄^2? had negligible impact while HCO₃^? and humic acid inhibited the degradation of AO7. Furthermore, radical scavenger experiments and methyl phenyl sulfoxide (PMSO) transformation assay indicated that sulfate radical, hydroxyl radical, and ferryl ion (Fe(IV)) were the dominant reactive species involved in the Cys/Fe(III)/PMS process. Finally, based on the results of gas chromatography-mass spectrometry, several AO7 degradation pathways, including N=N cleavage, hydroxylation, and ring opening were proposed. This study provided a new insight to improve the efficiency of Fe(III)/PMS process by accelerating Fe(III)/Fe(II) cycle with Cys.     

Spectroscopic Evidence of in situ Formation of a Novel Tetrakis(Tetrazolato)Iron Compound

In an attempt to synthesize the complex [Fe(CN)₅(N₂)]^3- by reaction of Na[Fe(CN)₅(NO)]·2H₂O with azide followed by treatment with NO[SbCl₆], a similar method to that used by Feltham to obtain trans-[RuCl(N₂)(das)₂]Cl₂ from trans-[RuCl(NO)(das)₂]Cl₂, we found spectroscopic evidence that excess azide reacts with the CN^- ligands to generate tetrazolato groups C-coordinated to Fe. Initial results suggest that the obtained compound is sodium azidotris(2H-tetrazolato)(5H-tetrazolato)iron(0). The spectroscopic evidence also indicates that these heterocycles are destroyed by reaction with NO[SbCl₆], and the CN^- groups are regenerated. Here we present the characterization of these complexes by IR, ¹³C NMR, conductivity measurements, elemental analysis and magnetic susceptibility.     

Massenspektrometrische Messung der Stabilität der gasförmigen Komplexe MAl2Cl8 (M  Be,Fe, Zn,Cd, Pt) Der Zusammenhang der Stabilität der Gaskomplexe MAl2Cl8 mit den Koordinationszahlen im festen Dichlorid

Mass Spectrometric Measurements of the Stability of the Gaseous Complexes MAl₂Cl₈ (M ? Be, Fe, Zn, Cd, Pt). Connection between the Stability of the Complexes MAl₂Cl₈ and the Coordination of M and Cl in the Solid Dichloride The equilibria MCl_2,s + Al₂Cl_6,g ? MAl₂Cl_8,g mit (M ? Fe, Zn, Cd, Pt) have been measured by mass spectrometry (effusion from double cells). The corresponding equilibrium with BeCl₂ has been calculated from older measurements. All the ΔH° and ΔS° data of this type of reaction have been collected from the literature. A clear connection exists between the thermodynamic data and the coordination of M and Cl in the solid dichlorides.     

Study of zinc thiocarbamide chloride,a single-source precursor for zinc sulfide thin films by spray pyrolysis

Thermal decomposition of the title compound, Zn(tu)₂Cl₂ (tu=thiourea), was studied up to 1200°C in dynamic inert (N₂) and oxidative (air) atmospheres using simultaneous TG/DTA techniques. In addition, XRD and IR were employed ex situ to resolve the reaction mechanism and products. Cubic ZnS (sphalerite) is formed below 300°C in both atmospheres and is observed until 760°C, whereafter it transforms in nitrogen to the hexagonal ZnS (wurtzite). EGA by FTIR revealed the complexity of the decomposition reactions involving also the evolution of H₂NCN, which reacts to form hexagonal ZnCN₂ as revealed by an XRD analysis. This revised version was published online in July 2006 with corrections to the Cover Date.