Metal Bromides Research Articles

Hierarchically porous monoliths based on low-valence transition metal (Cu, Co, Mn) oxides: gelation and phase separation.

Hierarchically porous monoliths based on copper (Cu), cobalt (Co) and manganese (Mn) oxides with three-dimensionally (3D) interconnected macropores and open nanopores were prepared using metal bromides as precursors via a sol–gel process accompanied by phase separation. The difficulty of gelation for low-valence metal cation was overcome by introducing a highly electronegative Br atom near to the metal atom to control the rates of hydrolysis and polycondensation. The 3D interconnected macropores were obtained using appropriate polymers to induce phase separation. The domain sizes of macropores and skeletons can be controlled by reaction parameters such as concentration and/or average molecular weight of polymers, and the amount of hydrochloric acid. The crystalline metal oxide monoliths with their 3D interconnected macroporous structure preserved were obtained after heat treatment in air.

Magnesium tetraorganyl derivatives of group 13 metals as intermediate products in the synthesis of group 13 metal alkyls and aryls

Reactions of organomagnesium halides with group 13 metal halides lead to the formation of R3M type compounds (R = alkyl, aryl; M = Al, Ga, In) and are considered as the simplest methods of R3M compound syntheses. These seemingly simple reactions reveal a much more complex chemistry involving mixed magnesium‐group 13 metal compounds. To elucidate the reaction course of reactions of organomagnesium halides with group 13 metal halides, we have studied reactions of R3M with organomagnesium halides. The interaction of Et3M with R1MgX led to the formation of following products being mixtures of crystalline ionic complexes with the general composition of [Et4‐nR1nM]−[XMg (thf)5]+·(thf): [Et2.2Al(CH=CH2)1.8]−[BrMg (thf)5]+·(thf) (1), [Et3Ga(CH=CH2)]−[BrMg (thf)5]+·(thf) (2), [Et4Al]−[BrMg (thf)5]+·(thf) (3), [Et4Ga]−[BrMg (thf)5]+·(thf) (4), [Et2.9Al(C6H5)1.1]−[BrMg (thf)5]+·(thf) (5), [Et2.9Ga(C6H5)1.1]−[BrMg (thf)5]+·(thf) (6), [Et3.4GaMe0.6]−[IMg (thf)5]+·(thf) (7) and [Et4In]−[BrMg (thf)5]+·(thf) (8). A comparison of the production course of group 13 metal trialkyls R3M with a thermal decomposition of 1–8 products showed that reactions of MX3 with RMgX (X = Br, I; R = alkyl, aryl) yield initially intermediate ionic compounds, which must then be thermally decomposed to obtain pure R3M compounds. If group 13 metal bromides and iodides, and alkyl (aryl)magnesium bromides and iodides in thf are used, only intermediate products with the [R4M]−[XMg (thf)5]+·(thf) structure are formed.

Extraction of Iron(III) with Tributyl Phosphate from Bromide Solutions

The extraction of iron(III) with tributyl phosphate from bromide aqueous solutions in the electrochemical processing of natural waters and brines was studied. It was found that iron(III) is extracted from solutions of alkali metal bromides in the form of the complex salt MFeBr4 at a salt concentration of more than 4 M. Extraction increases in the series KFeBr4 < NaFeBr4 < LiFeBr4. Extraction products are largely susceptible to electrolytic dissociation in the organic phase. The optimal conditions for the extraction of iron(III) bromide and its return to the technological process are determined.

Crystal structure of metal (I) bromide complexes containing 1-(4-nitrophenyl)thiourea and triphenylphosphine ligands

Crystal structure of metal (I) bromide complexes containing 1-(4-nitrophenyl)thiourea and triphenylphosphine ligands

Thermodynamic modeling of the MBr-BaBr2 (M=Alkali metals) systems

The complete thermodynamic optimizations of MBr-BaBr2 (M = Li, Na, K, Rb, Cs) systems were performed based on thermodynamic principles using CALPHAD approach. In this work, the existence of BaBr2-based solid solubility was firstly evaluated according to the corresponding liquid curves in available literature by the limiting liquidus slope equation and ideal liquid curve. The liquid enthalpy of mixing for LiBr–BaBr2 binary system was calculated via empirical prediction method. The Gibbs energy of liquid molten mixtures were modeled by the substitutional solution model (SSM) and the associate solution model (ASM), while that of the double salts were processed into stoichiometric compounds based on the Neumann-Kopp technique. The thermodynamic database with a series of thermodynamic properties and phase equilibria data of investigated systems were successfully established by optimizing model parameters. The simulated results could provide theoretical guidance and technical support, as well as applying in the design for the multi-components eutectic materials by combination with the binary alkali metal bromide systems.

Estimation of Thermodynamic Properties of Metal Hydroborates

AbstractMetal hydroborates from M(BH4)n to Mx(B12H12)y currently attract a strong interest for potential applications in the field of hydrogen storage and more recently as solid ionic conductors. While thermodynamic data for the alkali borohydrides (MBH4) are well known, experimental data for other compounds are cruelly lacking. Using a combination of theoretical (DFT) and experimental data, we calculate the lattice enthalpy for a series of borohydrides. The comparison with literature data show that these lattice enthalpies are very similar to those of the corresponding metal bromides. This similarity is at the origin of a good correlation between the formation enthalpy of bromides and borohydrides which is then used to estimate the previously unknown formation enthalpy of MII(BH4)2 (MII=divalent cation) and Ln(BH4)3 (Ln=lanthanide). The Gibbs free energy of formation of M2(B12H12) (M=alkali metal) is also estimated.

MgFeAl layered double hydroxide prepared from recycled industrial solid wastes for CO2 fixation by cycloaddition to epoxides

MgFeAl trimetallic layered double hydroxide (LDH) was prepared using industrial solid wastes of red mud and ferronickel slag, and exfoliation of the LDH by acetone washing resulted in a final product with high surface area (319 m2/g). It showed a CO2 adsorption capacity of 70.2 mg/g at 298 K and 1 bar, which was somewhat higher than that of a similar LDH synthesized using pure chemicals (63.8 mg/g). The LDH was tested as a catalyst for solvent-free CO2 cycloaddition to various epoxides. Significant conversion of epoxides and high selectivity to the corresponding cyclic carbonates were obtained under mild reaction conditions. The LDH achieved an excellent result of 98.0% conversion of epichlorohydrin and 98.2% selectivity to the cyclic carbonate in the presence of tetrabutylammonium bromide as co-catalyst at 50 °C and 5 bar after 7 h, catalyzed by the combination of Lewis acidic metal sites and bromide ions. The LDH was recovered after the reaction and maintained good catalytic performances after five repeated runs without any significant loss in catalytic activity. This work demonstrated that effective CO2 capture/utilization could be achieved simultaneously using a porous material easily prepared from industrial wastes.

(CH3 NH3 )AuX4 ⋅H2 O (X=Cl, Br) and (CH3 NH3 )AuCl4 : Low-Band Gap Lead-Free Layered Gold Halide Perovskite Materials.

Perovskite solar cells have recently enabled power conversion efficiency comparable to established technologies such as silicon and cadmium telluride. Ongoing efforts to improve the stability of halide perovskites in ambient air has yielded promising results. However, the presence of toxic heavy element lead (Pb) remains a major concern requiring further attention. Herein, we report three new Pb-free hybrid organic-inorganic perovskite-type halides based on gold (Au), (CH3 NH3 )AuBr4 ⋅H2 O (1), (CH3 NH3 )AuCl4 ⋅H2 O (2), and (CH3 NH3 )AuCl4 (3). Hydrated compounds 1 and 2 crystallize in a brand-new structure type featuring perovskite-derived 2D layers and 1D chains based on pseudo-octahedral AuX6 building blocks. In contrast, the novel crystal structure of the solvent-free compound 3 shows an exotic non-perovskite quasi-2D layered structure containing edge- and corner-shared AuCl6 octahedra. The use of Au metal instead of Pb results in unprecedented low band gaps below 2.5 eV for single-layered metal chlorides and bromides. Moreover, at room temperature the three compounds show a weak blue emission due to the electronic transition between Au-6s and Au-5d, in agreement with the density function theory (DFT) calculation results. These findings are discussed in the context of viability of Au-based halides as alternatives for Pb-based halides for optoelectronic applications.

A Facile and Versatile "Click" Approach Toward Multifunctional Ionic Metal-organic Frameworks for Efficient Conversion of CO2.

Ionic metal-organic frameworks (IMOFs) that integrate synergistic Lewis-acid sites (intrinsic metal centers of the frameworks) and nucleophilic anions (halides encapsulated within pores) are intriguing platforms for the design of fully heterogeneous catalytic systems for cycloaddition of CO2 to epoxides. A new, facile and versatile synthetic approach has been used to fabricate triazolium-based IMOFs for the first time. The approach makes use of azide-alkyne click chemistry and subsequent N-alkylation to post-synthetically create a cationic triazolium ring and introduce exchangeable counteranions at the same time. The IMOFs are efficient and recyclable heterogeneous catalysts for CO2 conversion under mild and cocatalyst-free conditions. In particular, the click-accessible triazolium ring provides a handle to incorporate further functionality. The MIL-101-tzmOH-Br catalyst, which integrates hydrogen-bonding hydroxy groups besides metal centers and bromide anions, shows superior catalytic performance under mild conditions.

Production and use of radioactive [82Br]KBr in high-temperature corrosion studies

The applicability of radioactive species in high-temperature research as tracers was studied with KBr and an Nb-stabilised austenitic stainless steel. KBr-induced high-temperature corrosion was addressed by using radioactive [82Br]KBr and measuring the radioactivity of the sample surface with a high-resolution phosphor imaging device.Neutron activation by cyclotron proved to be a very cost-effective way to produce radioactive [82Br]KBr with a high radionuclidic purity and a negligible level of unwanted side products. KBr reacts rapidly with steel, forming potassium chromate and metal bromides, both of which are reducing the protective properties of the surface oxide through chromium depletion and increasing porosity.

Thermodynamic Analysis on the Oxidative Pyrolytic Treatment of Electric Arc Furnace Dust–TBBA Blends

This contribution reports a thermodynamic assessment for the bromination of electric arc furnace dust (EAFD) by-products sourced from thermal degradation of tetrabromobisphenol A (TBBA); i.e., the most widely deployed brominated flame retardant. Upon TBBA’s pyrolysis, HBr is released in conjunction with several volatile organic compounds leaving a solid carbonaceous residue. EAFD contains appreciable quantities of zinc, iron, and lead oxides. These oxides can react with HBr to form volatile metal bromides when the EAFD is added to the TBBA as a bromination agent. The selective bromination of zinc and lead contained in EAFD was thermodynamically evaluated under both oxidative and inert pyrolytic conditions while considering the effects of several variables. These factors span temperature, loads of TBBA, the presence of oxidizing agent, and the effect of the presence of other common EAFD’s constituents such as sodium, potassium, calcium, silicon, and sulfur. It was found that a 100% extraction (based on thermodynamic feasibility) of both zinc and lead can be achieved for a mixture containing 60% EAFD and 40% TBBA (contaminated with minor amounts of iron) when pyrolyzed under inert conditions. However, when a thermal treatment is performed in the presence of oxygen, complete thermodynamic-based recovery of zinc and lead recoveries can be achieved at a lower temperature with no iron content. Removal of sodium and potassium chloride from EAFD prior to pyrolysis by washing, under oxidizing condition, can also result in a profound selectivity in zinc and lead bromination. The behavior of other elements during bromination process was also discussed.

Extraction of metal bromides from chloride brines with mixtures of molecular iodine and tributyl phosphate

The process of recovery by direct extraction of metal bromides from calcium chloride brines using mixtures of molecular iodine with tributyl phosphate has been studied. It was found that iodine significantly increases the recovery of the bromides of alkali and alkaline earth metals due to the formation of hydrophobic iodine complexes with the halide anions. Bromides of calcium and lithium are the most selectively extracted. The extracted complexes significantly dissociate into ions in the organic phase. The extraction of calcium halide over a wide range of its concentration in an aqueous solution results in the extraction of a mixed chloride-bromide salt. This is due to a significant difference in the separation factors for bromide and chloride ions in the interphase exchange reactions for the halide ions of the inner and outer coordination spheres of the extracted complex.

Bromine fixing ability of electric arc furnace dust during thermal degradation of tetrabromobisphenol: Experimental and thermodynamic analysis study

This work reports on the bromine fixing ability of a typical electric arc furnace dust (EAFD) upon its co-pyrolysis with tetrabormobisphenol (TBBA), the most widely used brominated flame retardant) both experimentally and theoretically following thermodynamic calculations. Experimentally, the following variables were considered in this investigation: EAFD: TBBA mass ratio (1:1, 1:2 and 1:3), pyrolysis heating rate and its final temperature and the effect of the NaCl and KCl presence in the dust. In the thermodynamic analysis the same parameters were studied excluding the heating rate. According to thermodynamic calculations, it was found that almost 100% of bromine, released as HBr during the thermal decomposition of TBBA, can be fixed by EAFD as metal bromides when 1:1 and 1:2 ratios where used. These metal bromides remain mainly in the solid form below 400 °C; above this temperature they commence evaporation leaving the reaction system. At 1:3 ratio almost 10% of the initial bromine contents is released in HBr gaseous form. Experimentally, it was found that about 70% of HBr is captured by EAFD when 1:1 and 1:2 ratios were used at temperatures below 350 °C, however, only 53% were captured when ratio 1:3 was used. At all conditions, the escaped gaseous HBr was as low as 6%. It was also found that high heating rates negatively affected the metal oxides ‘capacity to capture emitted HBr.

Improving bromine fixation in co-pyrolysis of non-metallic fractions of waste printed circuit boards with Bayer red mud

A method to improve bromine fixation by co-pyrolysis of non-metallic fractions (NMFs) of waste printed circuit boards (WPCBs) with Bayer red mud (RM) has been developed. More than 78.59 wt% of bromine was fixed into the solid residues with an addition of 15 wt% RM after co-pyrolysis at 500 °C, comparing with 36.42 wt% without the RM addition. Metal oxides (Fe2O3, Al2O3, TiO2, and Na2O, etc.) in the RM contributed significantly to the bromine fixation. The bromine fixation percentages were 62.94, 65.05, 47.24, and 49.05 wt% with an individual addition of 15 wt% Fe2O3, Na2O, Al2O3, and TiO2, respectively. Metal oxides in the RM showed synergistic effects on the bromine fixation, and this can be attributed to the secondary reaction of Na2O and bromine decomposed from FeBr3. The mechanisms of bromine fixation by RM are formation of Br-M (M: Fe, Al, Ti, and Na) and OH bonds generated from the direct elimination and a two-step of dissociative adsorption and β-H elimination reactions between metal oxides and bromide.

Pyrolysis kinetics of tetrabromobisphenol a (TBBPA) and electric arc furnace dust mixtures

This work assesses the decomposition kinetics and the overall pyrolysis behavior of Tetrabromobisphynol A (TBBPA) mixed with Electric Arc Furnace Dust (EAFD) using experimental data from thermogravimetric analysis (TGA). Mixtures of both materials with varying EAFD:TBBPA ratios (1:1, 1:2, 1:3 and 1:4) were pyrolyzed in an inert atmosphere under dynamic heating conditions at different heating rates (5, 10, 30 and 50 °C/min). The pyrolysis of pure TBBPA proceeded through two decomposition steps: debromination and volatilization of debromination products. This is followed by char formation that also involves release of volatile organic matter. However, the pyrolysis of EAFD:TBBPA mixture proves to be more complex in nature due to the occurrence of parallel solid-liquid reactions that result in the release of HBr and other volatile organic compounds (VOC) coupled with bromination of metal oxides. Subsequent chemical events encompass evaporation of metal bromides and finally reduction of the remaining metal oxides, most notably iron oxide, into their metallic form by the char. Three models, namely, Kissinger, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS), were deployed to derive kinetics parameters. Generally, it was found that the presence of EAFD has led to an increase in the apparent activation energy for the first stage of TBBPA decomposition due to the reduced evaporation of TBBPA.

Computational study of SN2 reactions promoted by crown ether: Contact ion pair versus solvent‐separated ion pair mechanism

AbstractWe examined by quantum chemical methods the mechanism of SN2 reaction using metal bromide MBr (M = Na, K, Cs) and KX (X= F, Cl) in CH3CN promoted by crown ether (18‐crown‐6). We focus on whether the metal salts react as a contact ion pair (CIP; M+ and X– in close contact) or as a solvent‐separated ion pair (SSIP; M+ and X– at large distance). In SSIP mechanism, X– is removed far enough from M+ for the metal salt to be considered as “separated” by the effects of the crown ether and the solvent. In the CIP picture, conversely, the coordination of 18‐crown‐6 to M+ is not sufficient to overcome the powerful Coulombic interactions between M+ and X–. We find that the CIP route is favored for SN2 bromination processes using MBr (M = Na, K, Cs). For SN2 reaction using KF, the feasibility of the two pathways is essentially equal, whereas for SN2 chlorination by KCl the SSIP route is predicted to be favored.

Role of metal halides in coke formation during bitumen upgrading

Abstract Metal chlorides are naturally present in bitumen. The concern of such metal chlorides in downstream processing is related to physical processes. However, a previous study revealed that mild bromination of asphaltenes resulted in a product with increased hardness and that was insoluble in both aromatic and paraffinic solvents, like coke. It was then hypothesized that the naturally present metal chlorides could affect solids yield during thermal conversion. The hypothesis was investigated by performing thermal conversion of Athabasca vacuum residue at 400 °C for 1 h in the presence of 1 wt% of different metal bromides (NaBr, CaBr2, MgBr2, CoBr2, and ZnBr2). Metal bromides were chosen instead of metal chlorides because vacuum residue does not contain bromine and it would facilitate analysis. Control experiments were also prepared: i) conversion in the presence of a base (Mg(OH)2) and ii) conversion in the absence of a metal bromide and/or base. The results revealed that the presence of acidic metal bromides during thermal cracking increased solids yield. Formation of a hydrogen halide (irrespective of the type of the halogen composing the metal halide) is a required step for metal halides to contribute to coke formation. It was also observed that acidic metal bromides caused halogen transfer to solid and liquid products and that this transfer was not due to trapped metal bromide salts. Acidic metal bromides increased solid yield during conversion of Athabasca vacuum residue from 2.5 wt% to 4–10 wt%. The increase solids yield and halogen transfer by thermal conversion in the presence of acidic metal bromides was suppressed by the addition of a base, but it was not eliminated. Thermal cracking in the presence of a base, Mg(OH)2, decreased overall solid yield.

Cd(II) and Ni(II) complexes from aroyl hydrazones: Unravelling the intermolecular interactions and electronic, crystal structures through experimental and theoretical studies

Three complexes of Cd(II) 1, 2 and Ni(II), 3 were prepared from two different aroyl hydrozone ligands (HL1 (C15H13N3O4) & HL2 (C20H17N3O2)) using their respective metal bromides. Crystal structures of all the three complexes have been established and the anionic/neutral nature of the coordinating ligand is mainly dictated by the nature of the metal center used. Quantification of intermolecular interactions is done using Hirshfeld surface and 2D finger print analysis. The Electrostatic Potential (ESP) analysis reveals that 2 has a collective concentration of negative electrostatic potentials to one side of the molecule giving a perfect separation of charges. DFT/semiempirical calculations revealed the same, giving a very high dipole moment for the optimized geometry of 2. Analysis of frontier orbitals is done through DFT calculations at the B3LYP/def2-TZVP level of theory and atomic charge distributions are predicted using AIM method.

Surplus adsorption of bromide ion into π-conjugated carbon nanospaces assisted by proton coadsorption

Nanoporous carbons can preferentially adsorb bromide ions from an aqueous solution of alkali metal bromides, even on π-conjugated surfaces. Our results show a new adsorption mechanism whereby coadsorption of protons enhances the adsorption of the anions onto the carbons.

Complexes of Thiourea with Alkali Metal Bromides and Iodides: Structural Properties, Mixed-Halide and Mixed-Metal Materials, and Halide Exchange Processes

We report the preparation and structural properties of complexes of metal halides and thiourea with composition MX[thiourea]4 (MX = KBr, KI, RbI, CsI), together with the mixed-halide materials KBrnI1–n[thiourea]4 (0 < n < 1) and the mixed-metal materials KnCs1–nI[thiourea]4 (0 < n < 1). These materials are isostructural, with a tetragonal structure (space group P4/mnc) characterized by M+[thiourea]4 coordination columns along the 4-fold axis and halide anions located in channels in the region of space between adjacent columns and running parallel to the columns. For the mixed-halide materials, the stoichiometry KBrnI1–n[thiourea]4 depends on the bromide/iodide ratio in the crystallization solution; the crystalline complexes have a higher bromide/iodide ratio than the crystallization solution, indicating preferential incorporation of bromide within the complex. Soaking crystals of KBr0.61I0.39[thiourea]4 in iodide containing solutions leads to halide exchange, with the iodide to bromide ratio increasing relative to the parent crystal. Further experiments produced no evidence that these thiourea complexes can accommodate extended polyiodide networks.