Cs2.91Na1.34Fe3+0.25[Fe3O(SO4)6(H2O)3]·5H2O,a member of the Maus's salt family

The title compound, tricaesium sodium iron(III) μ₃‐oxido‐hexa‐μ₂‐sulfato‐tris[aquairon(III)] pentahydrate, Cs_2.91Na_1.34Fe³⁺_0.25[Fe₃O(SO₄)₆(H₂O)₃]·5H₂O, belongs to the family of Maus's salts, K₅[Fe₃O(SO₄)₆(H₂O)₃]·6H₂O, which is based on the triaqua‐μ₃‐oxido‐hexa‐μ‐sulfato‐triferrate(III) anion, [Fe₃O(SO₄)₆(H₂O)₃]⁵⁻, with Fe in a characteristically distorted octahedral coordination environment, sharing a common corner via an oxide O atom. Cs in four different cation sites, Na in three different cation sites and five water molecules link the anions in three dimensions and set up a crystal structure in which those parts parallel to (001) and within 0.05 < z < 0.95 have a distinct trigonal pseudosymmetry, whereas the cation arrangement and bonding near z∼ 0 generate a clear‐cut noncentrosymmetric polar edifice with the monoclinic space group C2. The structure shows some cation disorder in the region near z ∼ , where one Na atom in octahedral coordination is partly substituted by Fe³⁺, and a Cs atom is substituted by small amounts of Na on a separate nearby site. One Na atom, located on a twofold axis at z = 0 and tetrahedrally coordinated by four sulfate O atoms of two [Fe₃O(SO₄)₆(H₂O)₃]⁵⁻ units, plays a key role in generating the noncentrosymmetric structure. Three of the seven different cation sites are on twofold axes (one Na⁺ site and two Cs⁺ sites), and all other atoms of the structure are in general positions.     

X-ray diffraction and Mössbauer spectroscopy studies of LiFe0.5Ti1.5O4 – A new primitive cubic ordered spinel

LiFe_0.5Ti_1.5O₄ was synthesized by solid-state reaction carried out at 900 °C in flowing argon atmosphere, followed by rapid quenching of the reaction product to room temperature. The compound has been characterized by X-ray powder diffraction (XRD) and ⁵⁷Fe Mössbauer effect spectroscopy (MES). It crystallizes in the space group P4₃32, a = 8.4048(1) Å. Results from Rietveld structural refinement indicated 1:3 cation ordering on the octahedral sites: Li occupies the octahedral (4b) sites, Ti occupies the octahedral (12d) sites, while the tetrahedral (8c) sites have mixed (Fe/Li) occupancy. A small, about 5%, inversion of Fe on the (4b) sites has been detected. The MES data is consistent with cation distribution and oxidation state of Fe, determined from the structural data.The title compound is thermally unstable in air atmosphere. At 800 °C it transforms to a mixture of two Fe³⁺ containing phases – a face centred cubic spinel Li_(1+y)/2Fe_(5−3y)/2Ti_yO₄ and a Li_(z−1)/2Fe_(7−3z)/2Ti_zO₅ – pseudobrookite. The major product of thermal treatment at 1000 °C is a ramsdellite type lithium titanium iron(III) oxide, accompanied by traces of rutile and pseudobrookite.     

K6[Fe8.27(HPO3)12]: a new mixed‐valence iron phosphite

The title compound, hexapotassium octairon(II,III) dodecaphosphonate, exhibiting a two‐dimensional structure, is a new mixed alkali/3d metal phosphite. It crystallizes in the space group Rm, with two crystallographically independent Fe atoms occupying sites of m (Fe1) and 3m (Fe2) symmetry. The Fe2 site is fully occupied, whereas the Fe1 site presents an occupancy factor of 0.757 (3). The three independent O atoms, one of which is disordered, are situated on a mirror and all other atoms are located on special positions with 3m symmetry. Layers of formula [Fe₃(HPO₃)₄]²⁻ are observed in the structure, formed by linear Fe₃O₁₂ trimer units, which contain face‐sharing FeO₆ octahedra interconnected by (HPO₃)²⁻ phosphite oxoanions. The partial occupancy of the Fe1 site might be described by the formation of two [Fe(HPO₃)₂]⁻ layers derived from the [Fe₃(HPO₃)₄]²⁻ layer when the Fe1 atom is absent. Fe²⁺ is localized at the Fe1 and Fe2 sites of the [Fe₃(HPO₃)₄]²⁻ sheets, whereas Fe³⁺ is found at the Fe2 sites of the [Fe(HPO₃)₂]⁻ sheets, according to bond‐valence calculations. The K⁺ cations are located in the interlayer spaces, between the [Fe₃(HPO₃)₄]²⁻ layers, and between the [Fe₃(HPO₃)₄]²⁻ and [Fe(HPO₃)₂]⁻ layers.     

Tris{bis­[hydro­tris(1‐pyrazolyl)­borato‐κ3N2,N2′,N2′′]iron(III)} hexaiso­thio­cyanato­iron(III)

The title compound, [Fe(C₉H₁₀BN₆)₂]₃[Fe(NCS)₆] or [Fe^III(Tp)₂]₃[Fe^III(NCS)₆] [Tp is hydro­tris(1‐pyrazolyl)­borate], crystallizes in space group ; the asymmetric unit comprises one‐half of an [Fe(Tp)₂]⁺ cation, with its Fe atom on a crystallographic inversion centre, and one‐sixth of an [Fe(NCS)₆]³⁻ anion, on a site of symmetry. The anions and cations are stacked into a three‐dimensional supramolecular aggregate via two distinct types of weak C—H⋯π interactions.     

A charge‐transfer salt composed of methyl viologen and hexacyanidoferrate(II)

The methyl viologen dication, used under the name Paraquat as an agricultural reagent, is a well‐known electron‐acceptor species that can participate in charge‐transfer (CT) interactions. The determination of the crystal structure of this species is important for accessing the CT interaction and CT‐based properties. The title hydrated salt, bis(1,1′‐dimethyl‐4,4′‐bipyridine‐1,1′‐diium) hexacyanidoferrate(II) octahydrate, (C₁₂H₁₄N₂)₂[Fe(CN)₆]·8H₂O or (MV)₂[Fe(CN)₆]·8H₂O [MV²⁺ is the 1,1′‐dimethyl‐4,4′‐bipyridine‐1,1′‐diium (methyl viologen) dication], crystallizes in the space group P 2₁/c with one MV²⁺ cation, half of an [Fe(CN)₆]⁴⁻ anion and four water molecules in the asymmetric unit. The Fe^II atom of the [Fe(CN)₆]⁴⁻ anion lies on an inversion centre and has an octahedral coordination sphere defined by six cyanide ligands. The MV²⁺ cation is located on a general position and adopts a noncoplanar structure, with a dihedral angle of 40.32 (7)° between the planes of the pyridine rings. In the crystal, layers of electron‐donor [Fe(CN)₆]⁴⁻ anions and layers of electron‐acceptor MV²⁺ cations are formed and are stacked in an alternating manner parallel to the direction of the −2a + c axis, resulting in an alternate layered structure.     

Photomagnetism in CxCo4[Fe(CN)6](8+x)/3·n H2O Prussian blue analogues: looking for the maximum photo-efficiency

A family of CoFe Prussian blue analogues C_xCo₄[Fe(CN)₆]_(8+x/3)□_(4–x)3 (x = amount of alkali cation inserted per conventional cell, C = Na, K, Rb, Cs; □ = [Fe(CN)₆] vacancy) have been synthesized and characterized. Their photomagnetic properties have been investigated by magnetic measurements before and after irradiation and X-ray diffraction under continuous irradiation. We show that the photo-induced magnetism depends on several parameters: (i) the amount of Co^III–Fe^II diamagnetic excitable pairs per cell; (ii) the amount of [Fe(CN)₆] vacancies, and (iii) the amount and nature of the alkali cations per cell. We evidence a discontinuity in the properties' change when the amount of alkali cation x varies, around x = 1. For x < 1, there is an excitation of diluted Co^III–Fe^II diamagnetic pairs in a phase mainly composed of magnetic Co^II–Fe^III entities within the same structural phase through a second-order continuous transformation. For x ≥ 1, the formation of domains mainly composed of Co^II–Fe^III* metastable magnetic pairs in a phase mainly composed of Co^III–Fe^II diamagnetic ones through a first-order discontinuous transition is observed. The study points out that sodium derivatives are more efficient than the others. Among them, Na₁Co₄[Fe(CN)₆]₃□₁ is predicted to be the most efficient one. To cite this article: A. Bleuzen et al., C. R. Chimie 6 (2003).     

Synthesis and Characterization of [Fe3(As3)3(As4)]3−, a Binary Fe/As Zintl Cluster With an Fe3 Core

We report here the synthesis and structural characterization of the first binary iron arsenide cluster anion, [Fe₃(As₃)₃(As₄)]³⁻, present in both [K([2.2.2]crypt)]₃[Fe₃(As₃)₃(As₄)] ( 1 ) and [K(18-crown-6)]₃[Fe₃(As₃)₃(As₄)]⋅en ( 2 ). The cluster contains an Fe₃ triangle with three short Fe−Fe bond lengths (2.494(1) Å, 2.459(1) Å and 2.668(2) Å for 1 , 2.471(1) Å, 2.473(1) Å and 2.660(1) Å for 2 ), bridged by a 2-butene-like As₄ unit. An analysis of the electronic structure using DFT reveals a triplet ground state with direct Fe−Fe bonds stabilizing the Fe₃ core.     

Über Geordnete Perowskite mit Kationenfehlstellen. II. Der Ersatz von UVI durch NbV in Ba2Gd0,67□0,33UO6

On Ordered Perovskites with Cationic Vacancies. II. The Incorporation of Nb^V in Ba₂Gd_0,67□_0,33UO₆ In Ba₂Gd_0.67□_0.33UO₆ a complete substitution of U^VI by Nb^V is possible by filling the cationic vacancies (x-phase: Ba₂Gd_0.67+0.33xU_1?xNb_xO₆). For the y-Phase (Ba₂Gd_0.67U_1?yNb_yO_6?0.5y) solid solutions are formed only for y ? 0.5. The properties of both phases are studied by x-ray and spectroscopic methods. In Ba₂GdNbO₆ – in contrary to the complete ordered Ba₂GdTaO₆ – the order of gadolinium and niobium id partial.     

Ionic Liquids with More than One Metal: Optical and Electrochemical Properties versus d-Block Metal Combinations

Thirteen N-butylpyridinium salts, including three monometallic [C₄Py]₂[MCl₄], nine bimetallic [C₄Py]₂[M_1−x^aM_x^bCl₄] and one trimetallic compound [C₄Py]₂[M_1−y-z^aM_y^bM_z^cCl₄] (M=Co, Cu, Mn; x=0.25, 0.50 or 0.75 and y=z=0.33), were synthesized and their structure and thermal and electrochemical properties were studied. All compounds are ionic liquids (ILs) with melting points between 69 and 93 °C. X-ray diffraction proves that all ILs are isostructural. The conductivity at room temperature is between 10⁻⁴ and 10⁻⁸ S cm⁻¹. Some Cu-based ILs reach conductivities of 10⁻² S cm⁻¹, which is, however, probably due to IL dec. This correlates with the optical bandgap measurements indicating the formation of large bandgap semiconductors. At elevated temperatures approaching the melting points, the conductivities reach up to 1.47×10⁻¹ S cm⁻¹ at 70 °C. The electrochemical stability windows of the ILs are between 2.5 and 3.0 V.     

Red and yellow solvates of chloro­(2,2′:6′,2′′‐terpyridine)platinum(II) chloride and Pt⋯Pt inter­actions

Crystallization of chloro­(2,2′:6′,2′′‐terpyridine)platinum(II) chloride from dimethyl sulfoxide yields a red polymorph, [PtCl(C₁₅H₁₁N₃)]Cl·C₂H₆OS, (I), which exhibits stacking along the a axis through pairs of Pt⋯Pt(−x, −y, −z) inter­actions of 3.3155 (8) Å. The cations are further associated through close Pt⋯Pt(1 − x, −y, −z) distances of 3.4360 (8) Å. Recrystallization from water gives a mero­hedrally twinned yellow–orange dihydrate form, [PtCl(C₁₅H₁₁N₃)]Cl·2H₂O, (II), with pairwise short Pt⋯Pt(1 − x, 2 − y, −z) contacts of 3.3903 (5) Å but no long‐range stacking through the crystals. Inter­pair Pt⋯Pt(−x, 2 − y, −z) distances between cation pairs in the hydrate are 4.3269 (5) Å.     

VII Zwei Oxidationsstufen und vier verschiedene Koordinationen von Eisen in einer Verbindung. Synthese,Kristallstruktur und spektroskopische Charakterisierung von 1,4‐Dimethylpiperazinium‐Chloroferrat(II,III), (dmpipzH2)6[FeIICl4]2[FeIIICl4]2[FeIICl5] [FeIIICl6]

Halogeno Metallates of Transition Elements with Cations of Nitrogen‐containing Heterocyclic Bases. VII Two Oxidation States and Four Different Iron Coordinations in one Compound. Synthesis, Crystal Structure, and Spectroscopic Characterization of 1,4‐Dimethylpiperazinium Chloroferrate(II, III), (dmpipzH₂)₆[Fe^IICl₄]₂[Fe^IIICl₄]₂[Fe^IICl₅] [Fe^IIICl₆] The title compound being stable on air crystallizes from aqueous hydrochloric acid solutions in the trigonal space group R3 with a = 13,197(1), c = 38,405(6) Å. Besides the cations in chair form, the structure contains six discrete, mononuclear chloroferrate anions arranged on a threefold axis. Tetrahedral, octahedral, and, for the first time with iron(II), trigonal bipyramidal metal coordinations occur. Four sub‐spectra contributing to the ⁵⁷Fe Mössbauer spectrum can be distinguished and have been attributed to all four types of chloroferrate anions in the structure. The Raman spectroscopic investigation of orientated single crystals allows to recognize polarized and non‐polarized vibrations as well as to attribute all observed frequencies.     

Garnets with dodecahedral rare earths and scandium,octahedral scandium,and tetrahedral iron. I. Compositional and structural studies

It has been found possible to prepare garnets with magnetic trivalent rare-earth ions filling all or most dodecahedral sites while nonmagnetic Sc³⁺ ions fill all octahedral sites and magnetic Fe³⁺ ions fill all or most tetrahedral sites. Phase-pure garnets found include {RE_3?ySc_y}[Sc₂](Fe₃)O₁₂, where RE is Sm, Eu, Gd, Tb, or Dy, and y can be zero with Sm and Eu; {Nd₃}[Sc₂](Fe_zGa_3?z)O₁₂; and other NdScFe garnets with small amounts of Y, Gd, or Lu added in order to bring z up to 3. Results are interpreted in terms of “size factor” and “comfort factor.”     

Aurophilic interactions in μ‐p‐phenyl­enediethynyl‐bis[(trimethyl phosphite)gold(I)] dichloro­methane hemisolvate

The title compound, [Au₂(C₁₀H₄)(C₃H₉O₃P)₂]·0.5CH₂Cl₂, is a linear monomer in which each Au atom is coordinated by one acetylene and one phosphite group. Molecules are connected through aurophilic interactions, one short and one longer, approximately perpendicular to the intramolecular di(gold acetylide) unit, with an Au⋯Au(x, 1 − y, + z) distance of 3.1733 (2) Å and an Au⋯Au(−x, y, − z) distance of 3.5995 (3) Å. Comparison with related compounds exhibiting aurophilic interactions shows that the packing architecture is not determined by steric factors alone.     

The bis(acetonitrile‐κN)bis[N,N‐bis(diphenylphosphanyl)ethanamine‐κ2P,P′]iron(II) tetrabromidoferrate(II) and μ‐oxido‐bis[tribromidoferrate(III)] complex salts

Orange crystals of bis(acetonitrile‐κN)bis[N,N‐bis(diphenylphosphanyl)ethanamine‐κ²P,P′]iron(II) tetrabromidoferrate(II), [Fe(CH₃CN)₂(C₂₆H₂₅NP₂)₂][FeBr₄], (I), and red crystals of bis(acetonitrile‐κN)bis[N,N‐bis(diphenylphosphanyl)ethanamine‐κ²P,P′]iron(II) μ‐oxido‐bis[tribromidoferrate(III)], [Fe(CH₃CN)₂(C₂₆H₂₅NP₂)₂][Fe₂Br₆O], (II), were obtained from the same solution after prolonged exposure to atmospheric oxygen, resulting in partial oxidation of the [FeBr₄]²⁻ anion to the [Br₃FeOFeBr₃]²⁻ anion. The asymmetric unit of (I) consists of three independent cations, one on a general position and two on inversion centres, with two anions, required to balance the charge, located on general positions. The asymmetric unit of (II) consists of two independent cations and two anions, all on special positions. The geometric parameters within the coordination environments of the cations do not differ significantly, with the major differences being in the orientation of the phenyl rings on the bidentate phosphane ligand. The ethyl substituent in the cation of (II) and the Br atoms in the anions of (II) are disordered. The P—Fe—P bite angles represent the smallest angles reported to date for octahedral Fe^II complexes containing bidentate phosphine ligands with MeCN in the axial positions, ranging from 70.82 (3) to 70.98 (4)°. The average Fe—Br bond distances of 2.46 (2) and 2.36 (2) Å in the [FeBr₄]²⁻ and [Br₃FeOFeBr₃]²⁻ anions, respectively, illustrate the differences in the Fe oxidation states.     

Élaboration et carac′erisation de céramiques de type PHT substituées au tantale Pb1−x/2□x/2(HfyTi1−y)1−xTaxO3 (PTHT)

Preparation and characterization of tantalum-substituted PHT ceramics Pb_1−x/2□_x/2(Hf_yTi_1−y)_1−xTa_xO₃ (PTHT). This paper deals with the preparation of five oxalic precursors containing lead, hafnium, titanium and tantalum with Pb_1−x/2) [(NH₄)_{2(1−x)(1−y)+3x} H_2y(1−x)]_(2x/(2+x)) [(Hf_yTi_(1−y))_1−xTa_xO(C₂O₄)_(x+2)], dH₂O general formula [for each precursor y = 0.52 but x takes different values (0.01 ; 0.025 ; 0.05 ; 0.075 ; 0.1)]. The pyrolysis of the complex was performed with a slow heating rate. The thermolysis led to the oxides which were characterized from the microstructural point of view (XRD) and grain size distribution. After the sintering, the electrical properties of the ceramic were studied using Complex Impedance Spectroscopy.     

FeIII in a low‐spin state in caesium bis[3‐ethoxysalicylaldehyde 4‐methylthiosemicarbazonato(2–)‐κ3O2,N1,S]ferrate(III) methanol monosolvate

The synthesis and crystal structure (at 100 K) of the title compound, Cs[Fe(C₁₁H₁₃N₃O₂S₂)₂]·CH₃OH, is reported. The asymmetric unit consists of an octahedral [Fe^III(L)₂]⁻ fragment, where L²⁻ is 3‐ethoxysalicylaldehyde 4‐methylthiosemicarbazonate(2−) {systematic name: [2‐(3‐ethoxy‐2‐oxidobenzylidene)hydrazin‐1‐ylidene](methylamino)methanethiolate}, a caesium cation and a methanol solvent molecule. Each L²⁻ ligand binds through the thiolate S, the imine N and the phenolate O atoms as donors, resulting in an Fe^IIIS₂N₂O₂ chromophore. The O,N,S‐coordinating ligands are orientated in two perpendicular planes, with the O and S atoms in cis positions and the N atoms in trans positions. The Fe^III cation is in the low‐spin state at 100 K.     

Slow Magnetic Relaxation,Antiferromagnetic Ordering,and Metamagnetism in MnII(H2dapsc)-FeIII(CN)6 Chain Complex with Highly Anisotropic Fe-CN-Mn Spin Coupling

Reactions of [Mn(H₂dapsc)Cl₂] ⋅ H₂O (dapsc=2,6- diacetylpyridine bis(semicarbazone)) with K₃[Fe(CN)₆] and (PPh₄)₃[Fe(CN)₆] lead to the formation of the chain polymeric complex {[Mn(H₂dapsc)][Fe(CN)₆][K(H₂O)_3.5]}_n ⋅ 1.5n H₂O ( 1 ) and the discrete pentanuclear complex {[Mn(H₂dapsc)]₃[Fe(CN)₆]₂(H₂O)₂} ⋅ 4 CH₃OH ⋅ 3.4 H₂O ( 2 ), respectively. In the crystal structure of 1 the high-spin [Mn^II(H₂dapsc)]²⁺ cations and low-spin hexacyanoferrate(III) anions are assembled into alternating heterometallic cyano-bridged chains. The K⁺ ions are located between the chains and are coordinated by oxygen atoms of the H₂dapsc ligand and water molecules. The magnetic structure of 1 is built from ferrimagnetic chains, which are antiferromagnetically coupled. The complex exhibits metamagnetism and frequency-dependent ac magnetic susceptibility, indicating single-chain magnetic behavior with a Mydosh-parameter φ=0.12 and an effective energy barrier (U_eff/k_B) of 36.0 K with τ₀=2.34×10⁻¹¹ s for the spin relaxation. Detailed theoretical analysis showed highly anisotropic intra-chain spin coupling between [Fe^III(CN)₆]³⁻ and [Mn^II(H₂dapsc)]²⁺ units resulting from orbital degeneracy and unquenched orbital momentum of [Fe^III(CN)₆]³⁻ complexes. The origin of the metamagnetic transition is discussed in terms of strong magnetic anisotropy and weak AF interchain spin coupling.     

The pillared layered framework of Ba3(In1−xMx)2(HXO4)6 (0≤x≤1; M=Fe,Cr; X=P,As): synthesis,crystal structure,thermal stability and Mössbauer spectroscopy

The hydrothermal synthesis, single crystal structure analysis, spectroscopic and thermal stability studies of the compounds Ba₃(In_1−xM_x)₂(HXO₄)₆ (0≤x≤1; M=Cr, Fe; X=P, As) are reported. The 3D framework of these new phosphates can be described as a pillared layered framework. The metal cations (In³⁺, Fe³⁺, and Cr³⁺) occupy two crystallographically independent octahedral sites, M(1) and M(2). The layers are formed of M(2)O₆ octahedra and (HPO₄) tetrahedra sharing corners, with M(1)O₆ octahedra serving as pillars between adjacent layers. Single crystal study of Ba₃(In_0.5Fe_0.5)(HPO₄)₆ shows that indium and iron segregate between the two metal sites with Fe occupying primarily the site M(1) and In located primarily in M(2) site. Interactions between the building units within the layers occur through hydrogen bonding. Barium cations are located between the pillars, in 8-membered ring tunnels and are coordinated by 12 oxides. The phases loose three water molecules through condensation of six HXO₄ groups to form Ba₂M₂(X₂O₇)₃ at temperatures between 480 and 600 °C. Mössbauer spectroscopy shows the presence of high-spin Fe³⁺ in octahedral coordination.     

Bis­[tris(2,2′‐bi­pyridine‐κ2N,N′)­ruthenium(II)] hexa­cyano­ferrate(III) chloride octahydrate

In the title compound, [Ru^II(C₁₀H₈N₂)₃]₂[Fe^III(CN)₆]Cl·8H₂O, the [Ru(bpy)₃]²⁺ (bpy is 2,2′‐bi­pyridine) cations and water mol­ecules afford intriguing microporous honeycomb layers, while the [Fe(CN)₆]³⁻ anions and the remainder of the water mol­ecules form anionic sheets based on extensive hydrogen‐bonding networks. The cationic and anionic layers alternate along the c axis. The Fe atom in [Fe(CN)₆]³⁻ lies on an inversion centre and the axial cyano ligands are hydrogen bonded to the water mol­ecules encapsulated within the micropores [N⋯O = 2.788 (5) Å], giving an unusual interpenetration between the cationic and anionic layers. On the other hand, the in‐plane cyano ligands are relatively weakly hydrogen bonded to the water mol­ecules [N⋯O = 2.855 (7) and 2.881 (8) Å] within the anionic sheets.     

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.