Synthesis, structural characterization and ethylene polymerization behavior of complex [Ph4P][CrCl3{HB(pz)3}] [HB(pz)3 = hydrotris(1-pyrazolyl)borate]

Reaction of CrCl₃(THF)₃ with K[HB(pz)₃] in THF leads to the formation of the complex K[CrCl₃{HB(pz)₃}] (1). The salt metathesis of complex 1 with [Ph₄P]Br in CH₂Cl₂ yields the complex [Ph₄P][CrCl₃{HB(pz)₃}](2). The structure of complex 2 · CHCl₃ has been determined by single crystal X-ray diffraction. In the anion the metal centre shows a distorted octahedral geometry with the hydrotris(1-pyrazolyl)borate bonded as N,N′,N″-donor tripod ligand and three chloride atoms completing the co-ordination sphere. Complex 2 in the presence of MAO leads to the formation of an active catalyst for the polymerization of ethylene.     

Observations macroscopiques et microscopiques des produits d'insertion du graphite avec le trichlorure d'or

The intercalation of gold trichloride has been studied in the classical manner by the action of the vapour on graphite in a sealed tube[12]. Tables 1 and 5 summarize the results obtained with various samples of natural and artificial graphite and with carbon materials graphitized at high temperatures. Under optimal reaction conditions (245°C), a blue, richest ($\text{Δm}\text{mo}\text{= 200\%}$) product is obtained, of formula C_12.6AuCl₃: gold trichloride intercalates in the pure state (Table 2). Comparison of the results obtained by thermogravimetry (Fig. 1), dialatométry (Fig. 2) and X-ray analysis (Fig. 3) indicates that this final product C_12.6AuCl₃ is of first stage with an interplanar distance of 6.80Å (Table 3). Study of the relative intensities[17] of the (001) reflections allows stating that the gold trichloride intercalates are in the form of planar molecules Au₂Cl₆ (Table 4). Macroscopic observation of the pyrographite samples shows that the insertion occurs in an “all or nothing” manner[18]: during the reaction the layers are gradually deformed in the neighbourhood of the “invasion front” (Fig. 4) and when the intercalation is terminated, a pleating of the layers appears very clearly at the surface (Figs. 5 and 6). These dislocations visible on the edges of the samples (Fig. 7) are a manifestation of the “separation work” necessary for the intercalation which practically excludes the possibility of reagent layers inserted with a lower ratio than in C_12.6AuCl₃.Graphite and its intercalation compounds lend themselves only with difficulty to a microstructural study by visualization of the lattice planes (instability of the products under an electron beam, basal carbon planes invariably parallel to the grid support).Carbon blacks (Sterling MTG 3000°C) are small circular rods (θ < 1μ) graphitized throughout their mass (Fig. 8) which give with gold trichloride, rich products ($\text{Δm}\text{mo}\text{= 140\%}$), almost of the second stage. With these carbons, it was not possible to intercalate ferric or chromic trichloride[21]. The lattice distances measured on micrographs of the intercalated products (Fig. 9) allowed to identify the most contrasted fringes as direct representations of gold trichloride layers inserted between those of the carbon (the finer fringes). The different types of layers observed along the segment AB (Fig. 9) indicate a succession of different stages from A to B (1st-1st-2nd-3rd-4th-3rd-5th) which indicates the inhomogeneity of the products studied[10]. These results seem to corroborate the “statistical definition” of stage identifiable in the combination of graphite with the halogenides[8,19,22].     

Determination of the β ↔ αL′ transition in Ca2SiO4 to 7 KBAR

Differential thermal analysis in hydrostatic apparatus to 7 kbar shows that the β → α_L′ transition temperature in Ca₂SiO₄ linearly increases from 701° ± 2°C at 1 bar at the rate of 10.5 ± 0.5 deg kbar⁻¹. The α_L′ → β transition temperature is observed some 20°–30° lower in temperature than the β → α_L′ transition and no variation in this hysteresis with pressure is indicated.     

Two 1D [CuxIx]-based coordination polymers of tetraphosphine ligands

Diffusion reactions of CuI with N,N,N′,N′-tetra(diphenylphosphanylmethyl)ethylene diamine) (dppeda) and 1,4-N,N,N′,N′-tetra(diphenylphosphanylmethyl)benzene diamine (dpppda) in MeCN/toluene in a zigzag glass tube or solvothermal reactions of CuI and dppeda or dpppda in MeCN produced two [Cu_xI_x]-based coordination polymers, [Cu₂I₂(dppeda)]·2MeCN (1·2MeCN) and [Cu₄I₄(dpppda)]·MeCN (2·MeCN), respectively. Both compounds were characterized by elemental analysis, IR spectroscopy, ¹H and ³¹P{¹H} NMR, ESI-MS and thermogravimetric analysis, and their structures were determined by single crystal X-ray diffraction. In 1, [Cu₂I₂] cores are interconnected by dppeda ligands in a μ-η²:η² end-to-end mode to form a 1D chain, while in 2 stair-like [Cu₄I₄] cores are linked by dpppda ligands in a unique Z-shaped μ-η²:η² side-by-side mode to produce the other kind of 1D chain.     

Preparation and characterization of novel main-chain azobenzene polymers via step-growth polymerization based on click chemistry

A novel α-azide and ω-alkyne A–B type azobenzene monomer, 3′-ethynylphenyl[4-(4-azidobutoxy)phenyl]azobenzene (EAPA), was synthesized and used to generate a novel polymer via step-growth polymerization using 1,3-dipolar cycloaddition reaction under the catalysis of CuSO₄·5H₂O/sodium ascorbate/H₂O (“Click” chemistry). The structure of the resultant main-chain azobenzene polymer, PEAPA, was characterized by GPC, ¹³C NMR, UV–vis and FT-IR spectra. Thermal stability and crystallinity of PEAPA powder were studied by TGA and WAXD. The photo-induced trans–cis isomerization of PEAPA and EAPA in N,N′-dimethyl formamide (DMF) solution was investigated. Furthermore, the thermal cis–trans isomerizations of PEAPA and EAPA were also observed at 60 °C in dark. Thermal stability and trans–cis–trans isomerization behavior of PEAPA was compared with its non-triazole analog, PDHA.     

Thermal properties of the nitrogen-rich Ca-α-Sialons

Nitrogen-rich Ca-α-Sialon (Ca_xSi_12−2xAl_2xN₁₆ with x = 0.2, 0.4, and 0.8, 1.2 and 1.6) ceramics were prepared from the mixtures of Si₃N₄, AlN and CaH₂ powders in a hot press at 1800 °C using a pressure of 35 MPa and a holding time of 4 h, and then were investigated with respect to reaction mechanism, phase stability and oxidation resistance. In addition the sample with x = 1.6 was prepared in the temperature range 600–1800 °C using a pressure of 35 MPa and a holding time of 2 h. The α-Sialon phase was first observed at 1400 °C but the α-Si₃N₄ and AlN phases were still present at 1700 °C. Phase pure Ca-α-Sialon ceramics could not be obtained until the sintering temperature reached 1800 °C. The phase pure nitrogen-rich Ca-α-Sialon exhibited no phase transformation in the temperature range 1400–1600 °C. In general, mixed α/β-Sialon showed better oxidation resistance than pure α-Sialon in the low temperature range (1250–1325 °C), while α-Sialons with compositions located at α/β-Sialon border-line showed significant weight gains over the entire temperature range tested (1250–1400 °C). The phases formed upon oxidation were characterized by X-ray, SEM and TEM studies.     

Phase separation temperatures in the polystyrene—poly(α-methyl styrene)—methylcyclohexane system

The phase separation temperatures (PST) in the ternary system polystyrene (PS) (M_w = 1.75 × 10⁴ g mol⁻¹ — poly(α-methyl styrene) (PαMS) (M_w = 6.0 × 10⁴) — methylcyclohexane (MCH) and the binary systems PS-MCH and PαMS-MCH have been determined by using a He---Ne laser light-scattering apparatus over the total polymer weight fraction (W_{PS + PαMS}) range of 0.018 to 0.80 and various polymer blend ratios. The PST determined at a scattering angle of 0° agreed with those at 90° for the binary systems over polymer concentrations of 0.1 to 0.7 and for the ternary over W_{PS + PαMS} of higher than 0.3. Deviations of the PST determined at an angle of 90° from those at 0° were observed in the ternary system when W_{PS + PαMS} was lower than 0.3. Two phase separation temperatures, at which the intensity scattered from zero angle changed discontinuously, are observed at concentrations lower than W_{PS + PαMS} = 0.042 in the ternary system. The PST in the ternary system decreases monotonically with increasing W_{PS + PαMS} over 0.3 to 0.7. The phase diagram for the PS-PαMS-MCH system at W_{PS + PαMS} = 0.8 is characterized by a maximum PST around − 14°C.     

An oxide chain constructed from octamolybdate, a Keggin anion and a copper (II) – Tetrapyridylpyrazine binuclear unit

The hydrothermal reaction of MoO₃, CuSO₄·5H₂O, tetra-4-pyridylpyrazine (tpyprz), and diphenyldiarsonic acid in water at 140 °C for 48 h yielded the one-dimensional material [{Cu₂(tpyprz)(H₂O)₃}₂{Mo₈O₂₆}{Mo₁₂O₃₆(AsO₄)}]·8H₂O (1·8H₂O). The chain structure of 1·8H₂O is constructed from alternating β-octamolybdate clusters and molybdoarsonate Keggin clusters linked through {Cu₂(tpyprz)(H₂O)₃}⁴⁺ binuclear subunits. The Cu(II) sites are inequivalent with one copper bonding to two pyridyl donors and a pyrazine nitrogen of one terminus of the tpyprz ligand, two aqua ligands and an oxo-group of the cluster while the second copper site coordinates to the nitrogen donors of the other terminus of the tpyprz ligand, an aqua group, a terminal oxo-group of the cluster and a terminal oxo-group of the mixed valence {Mo₁₁^VIMo^VO₃₆(AsO₄)}⁴⁻ cluster. Crystal data: C₄₈H₆₀AsCu₄Mo₂₀N₁₂O₈₀: FW = 4332.96 Triclinic , a = 12.5087(5) Å, b = 13.6681(6) Å, c = 14.8980(6) Å, α = 92.196(1)°, β = 97.046(1)°, γ = 97.751(1)°, Z = 1, D_calc = 2.877 g cm⁻³; structure solution and refinement based on 12,333 reflections (Mo K_α, λ = 0.71073 Å) converged at R₁ = 0.0540 and wR₂ = 0.1115.     

Kinetics of reduction, composition and the stability constants of the zinc–maleic acid complexes in aqueous medium

Polarographic reduction of the zinc-maleic acid complexes has been studied at the dropping mercury electrode (dme) in aqueous medium at 30° and ionic strength 2.0 Gelling's method is used for determining the reversible half-wave potentials and the kinetics parameters (α and K_s) for the quasireversible reduction of the complexes. The value of α and K_s varied from 0.41 to 0.35 and 2.58 × 10⁻³ to 2.21 × 10⁻³ cm/s respectively with the ligand concentration changing from 0.00 to 0.60 M. Analysis of the polarographic characteristics ,of the system by the DeFord and Hume method gave the following values of the overall stability constants: β₁ = 50±2; β₂ = 160± 10 and β₃ = 2250 ± 50. The overall stability constants of the zinc-maleic acid complexes have also been calculated using the recently developed method of Mihailov. The resulting values are: β₁ = 29.9, β₂ = 301.4 and β₃ = 2025. Percentage distribution of the complex species present in the system is shown as a function of log/ligand concentration.     

Oxovanadium(IV) complex of β-alanine derived ligand immobilised on polystyrene for the oxidation of various organic substrates

Tridentate Schiff base (H₂fsal-β-ala) obtained from 3-formylsalicylic acid and β-alanine has been covalently bonded to divinylbenzene cross-linked chloromethylated polystyrene. This chelating resin, abbreviated as PS-H₂fsal-β-ala (PS = polymeric support), reacts with vanadyl sulfate in DMF to give polymer bound complex, PS-[VO(fsal-β-ala) · DMF], formation of which has been confirmed by various physiochemical methods such as elemental analysis, FT-IR and diffused reflectance spectra, thermo gravimetric analysis, and scanning electron micrograph. Catalytic potential of PS-[VO(fsal-β-ala) · DMF] has been tested for the oxidation of various organic substrates such as benzene, cumene, naphthalene, cyclohexane, styrene, cyclohexene and trans-stilbene in the presence of 30% H₂O₂ as an oxidant. Oxidation products obtained from each substrate have been characterised by gas chromatography and their identities confirmed by gas chromatography–mass spectrometry.     

Structure refinement of the as-synthesized and the calcined form of zeolite RUB-3 (RTE)

The structure analysis based on single crystal and powder data revealed that the framework structure of RUB-3 (structure type code RTE) consists of small [4⁴5⁴6²] building units and medium–large [4⁶5⁴6⁶8²] cages with a free volume of ca. 300 ų. Interconnected cages form a one-dimensional channel system with narrow, slightly elliptical pore openings (free diameter 3.6×4.3 Ų). ¹H–¹³C CP MAS NMR spectroscopy proved that the cages are occupied by disordered (±)-exo-2-aminobicyclo[2.2.1]heptane molecules which were used as templates during the synthesis. The unit cell composition of as-synthesized RUB-3 is (C₇H₁₃N)₂·[Si₂₄O₄₈]. The lattice parameters, bond lengths, bond angles and unit cell volumes are nearly identical for the as-synthesized [a=14.039(2) Å, b=13.602(2) Å, c=7.428(1) Å, β=102.22(3)°] and calcined form [a=14.018(1) Å, b=13.612(1) Å, c=7.418(1) Å, β=102.12(1)°] of RUB-3. The RTE structure even keeps its symmetry (C2/m) during the calcination process, indicating that the RTE framework topology is very rigid. All crystals are four-fold twins with twin planes {110}.     

Cu(II) bipyridine and phenantroline complexes: Tailor-made catalysts for the selective oxidation of tetralin

Mononuclear Cu(II) complexes have been synthesized, and their structure thoroughly characterized by electrospray ionization mass spectrometry (ESI-MS). These 2,2′-bipyridine and 1,10-phenantroline mononuclear Cu(II) complexes have been tested as catalysts in the partial oxidation of tetralin (1,2,3,4-tetrahydronaphthalene), using hydrogen peroxide as oxidant in acetonitrile/water as solvent.The complexes [Cu(bipy)₃]Cl₂·6H₂O (1), [Cu(bipy)₂Cl]Cl·5H₂O (2), [Cu(bipy)Cl₂] (3), [Cu(phen)₃]Cl₂·6H₂O (4), [Cu(phen)₂Cl]Cl·5H₂O (5), [Cu(phen)Cl₂] (6) were able to oxidize tetralin at room temperature, at high degrees of conversion (62.1% with 2) into α-tetralol and α-tetralon at 91% selectivity (81% in 1-tetralon).Depending on nature and number of ligands (bipyridine or phenantroline) surrounding Cu²⁺ cation, one was able to tailor both the activity toward tetralin oxidation, and the selectivity toward 1-tetralol and 1-tetralone products, but also to raise the yield in valuable α-tetralone.     

Preparation and characterization of chromium deposits obtained from molten salts using pulsed currents

The electroplating of chromium from fused chloride electrolytes was investigated. The experimental conditions were defined taking into account the mechanisms of the electrochemical reduction of CrCl₂ and of the chromium nucleation and electrocrystallization phenomena. Chromium was plated on various substrates from concentrated LiCl–KCl–CrCl₂ (600 to 800 mol m^–3 CrCl₂) electrolyte. Direct or pulsed current electrolysis were carried out under a dry argon atmosphere in the 400 to 440 °C temperature range. The shape of the current signals was chosen, taking into account the chromium electrocrystallization phenomena onto a foreign substrate, so as to obtain well-defined structures for the chromium layers. The chromium deposits were characterized by SEM and EDX analysis, and by microhardness determination. Uniform chromium electroplates of high purity, high adherence with no cracks, were obtained by using pulsed current: signals with cathodic pulses and open-circuit periods preceded by cathodic pre-pulses. With this current shape, the mean rate of the chromium electroplating process remained lower than 10 m h^–1. However, using a repeated of periodic cathodic pre-pulse/cathodic pulse/anodic pulse/open circuit sequences, the growth rate of compact chromium layers increased to 100 m h^–1 or more.     

A CdSO4-like 3-D framework constructed from monosodium substituted Keggin arsenotungstates and copper(II)-ethylenediamine complexes

A 6⁵·8 CdSO₄-like 3-D framework [Cu(en)₂]₃[α-AsW₁₁NaO₃₉]·2H₂O (1) constructed by monosodium-substituted Keggin arsenotungstates and copper(II)-ethylenediamine complexes (en = ethylenediamine) has been synthesized by reaction of Na₈[α-HAsW₉O₃₄]·11H₂O, CuCl₂·2H₂O and ethylenediamine under hydrothermal conditions and structurally characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction. Crystal data for 1: C₁₂H₅₂AsCu₃N₁₂NaO₄₁W₁₁, monoclinic, Cc, a = 20.409(9) Å, b = 16.737(8) Å, c = 16.561(7) Å, β = 104.607(7)°, V = 5474(4) Å³, T = 296(2) K; Z = 4, μ = 24.860 mm⁻¹, GOOF = 1.086, R₁ = 0.0284, wR₂ = 0.0759. To the best of our knowledge, 1 represents the first 6⁵·8 CdSO₄-like 3-D monovacant Keggin arsenotungstate derivative in polyoxometalate chemistry.     

Performances of mixed alcohols synthesis over potassium promoted molybdenum carbides

Molybdenum carbides, β-Mo₂C and α-MoC_1−X, promoted by K₂CO₃ were studied as catalysts for CO hydrogenation reactions at T = 573 K, P = 8.0 MPa, GHSV = 2000 h⁻¹, H₂/CO = 1.0. Unpromoted molybdenum carbides produced mainly light hydrocarbons under these conditions. Addition of K₂CO₃ as a promoter, however, both β-Mo₂C and α-MoC_1−X resulted in remarkable selectivity shift from hydrocarbons to alcohols. Moreover, the promoter of potassium enhanced the ability of chain propagation of β-Mo₂C and α-MoC_1−X with higher selectivity to C₂₊OH. Meanwhile, the investigation of the loadings of K₂CO₃ in β-Mo₂C and α-MoC_1−X revealed that the maximum of yield of alcohol was obtained at K/Mo (molar ratio) of 0.2 and 0.1, respectively. On K/β-Mo₂C catalysts, the distribution of hydrocarbons obeyed traditional linear A–S–F plot, while alcohols gave a unique linear A–S–F distribution with remarkable deviation of methanol compared with that of on β-Mo₂C catalyst. However, there was no significant difference between α-MoC_1−X and K/α-MoC_1−X catalysts about the distributions of alcohols and hydrocarbons; they both have similar linear A–S–F plots. Thus, the potassium promoter played a different role over β-Mo₂C and α-MoC_1−X catalysts upon the catalytic performance of mixed alcohols synthesis.     

Solvothermal synthesis of 1D and 2D cobalt(II) and nickel(II) coordination polymers with 2,5-dihydroxy-p-benzenediacetic acid

1D cobalt(II) and nickel(II) coordination polymers {[Co(dba)(H₂O)₄] · H₂O}_n (1) and {[Ni(dba)(H₂O)₄] · H₂O}_n (2) (H₂dba = 2,5-dihydroxy-p-benzenediacetic acid) were synthesized under low temperature solvothermal condition. When 4,4′-bipyridine (bpy) was introduced to the synthetic systems of 1 and 2, respectively, two novel 2D coordination polymers {[Co(dba)(bpy)] · 0.5H₂O}_n (3) and [Ni(dba)(bpy)(H₂O)₂]_n (4) with different structures were obtained. All of the compounds were characterized by elemental analysis, FT-IR, UV–Vis spectra and single crystal X-ray diffraction.     

Effect of sintering temperature on varistor properties and aging characteristics of ZnO–V2O5–MnO2 ceramics

The microstructure, electrical properties, dielectric characteristics, and DC accelerated aging behavior of the ZVM-based varistors were investigated for different sintering temperatures of 800–950 °C. The microstructure of the ZVM-based ceramics consisted of mainly ZnO grain and secondary phase Zn₃(VO₄)₂, which acts as liquid-phase sintering aid. The Zn₃(VO₄)₂ has a significant effect on the sintered density, in the light of an experimental fact, which the decreases of the Zn₃(VO₄)₂ distribution with increasing sintering temperature resulted in the low sintered density. The breakdown field exhibited the highest value (17,640 V/cm) at 800 °C in the sintering temperature and the lowest value (992 V/cm) at 900 °C in the sintering temperature. The nonlinear coefficient exhibited the highest value, reaching 38 at 800 °C and the lowest value, reaching 17 at 850 °C. The varistor sintered at 900 °C exhibited not only high nonlinearity with 27.2 in nonlinear coefficient, but also the highest stability, in which %ΔE_1 mA = −0.6%, %Δα = −26.1%, and %Δ tan δ = +21.8% for DC accelerated aging stress of 0.85 E_1 mA/85 °C/24 h.     

Synthesis and study of a new class of red pigments based on perovskite YAlO3 structure

A red pigment has been prepared by substituting chromium ions in aluminum ion sites in YAlO₃ perovskite structure. In a first step, effect of various mineralizers on YAlO₃ formation has been investigated, which resulted in decrease of formation temperature down to 1400 °C. In the next step, a red pigment corresponding to YAl_1−yCr_yO₃ (y = 0.05), has been prepared by heating a mixture containing Y₂O₃, Al₂O₃ and Cr₂O₃ at 1500 °C for 6 h. Later, effect of the doped chromium amount on the pigment redness (a^*) has been studied. The highest redness has been obtained when y was 0.04(YAl_1−yCr_yO₃). Application of the prepared red pigment in low and high temperature glazes, demonstrated its high chemical and thermal stability.     

Design and construction of two new polymers featuring macrocyclic subunits based on a rigid clamp-like ligand

Reaction of a rigid conjugated clamp-like ligand N,N′-bis(pyridin-3-yl)-2,6-pyridinedicarboxamide (bppdca) with ZnSO₄·7H₂O or CoSO₄·7H₂O resulted in the formation of two new polymers, namely, {[Zn₂(bppdca)(SO₄)₂(DMF)₂]·(DMF)}_n (1) and {[Co(bppdca)(SO₄)(CH₃OH)(DMF)]·H₂O}_n (2). Both 1 and 2 feature one-dimensional double-chain structures with macrocyclic subunits, and the chains further self-assemble into a higher-dimensional framework via the hydrogen-bonding and π–π stacking interactions. Fluorescence studies show that the free ligand displays a strong fluorescence emission in solid state at room temperature, but in 1 and 2, the complexation of the ligand with metal ions and weak intermolecular interactions make the fluorescence emission partial quenching.     

Die thermische deintercalation von graphitintercalationsverbindungen der arsen- und antimonchloridfluoride

In the reaction of AsCl₂F₃ with graphite, intercalation compounds of stage n = 3 are produced with an identity period of I_c = 1.49 nm. The stoichiometry of the compounds varies in consequence of the dissociation and dismutation reactions of AsCl₂F₃. The exfoliation of the crystals and the release of chlorine have been observed during heat treatment. The maximum thermal deintercalation is between 350 and 440°C. Only chlorine and arsenic trihalides, no pentahalides, have been detected by mass spectrometric analysis of the pyrolysis gases. Thermogravimetric investigations of SbCl_mF_5-m graphite intercalation compounds as well as mass spectrometric analyses of the pyrolysis gases show that in the deintercalation of the original intercalated pentahalides, their thermal dissociation as well as dismutation by halogen exchange overlap in the course of thermal decomposition. The conversion of stage 1 SbCl₄F graphite to stage 2 and the formation of dilute stage 2 SbCl₅ graphite as well as SbCl₄F graphite take place at 80–110°C. A high concentration of the pentahalides SbCl₅ and SbCl₄F respectively and a low concentration of trihalides have been found by mass spectrometry in the gas phase at 80–110°C. This low-temperature deintercalation is assumed to be a complete or partial emptying of galleries without a structural modification of the graphite layers. The structural conversions of stages n > 2 into stages n + 1 at higher temperatures of about 200 and 300°C are explained by a Daumas-Hérold domain model. Powdered natural graphite and synthetic graphite exhibit a preferred deintercalation of halides at 80–110°C. This may be explained by a higher density of diffusion paths and a lower ratio of crystallite sizes to domain sizes with respect to graphite flakes. The thermal dissociation of the pentahalides beginning at 190–200°C overlaps with the conversion of stage 2 to stage 3. At the same time chlorine is explosively released, leading to the exfoliation of the graphite flakes. The conversions of higher stages open intercalate islands in the crystal bulk and, consequently, the concentrations of the pentahalides and their dissociation products in the gas phase increase. The conversion of stage 3 to stage 4 occurs in the temperature range of 300–350°C; stages n > 4 degrade between 400 and 430°C. SbCl₂F₃ graphite as well as AsCl₂F₃ graphite evolves only the dissociation and dismutation products of the pentahalides. With an increase of temperature, the relative concentrations of SbF₃ and AsF₃ increase with respect to those of the Cl-containing trihalides; this is a consequence of dismutation with halogen exchange. The formation of polymeric neutral or anionic Sb halide species with fluorine bridges is presumably the reason for the dismutation reactions.