Thermal analysis on C<Subscript>6</Subscript>H<Subscript>10</Subscript>Ge<Subscript>2</Subscript>O<Subscript>7</Subscript>-doped MgB<Subscript>2</Subscript>

Additives to MgB₂ can improve the superconducting functional characteristics, such as critical current density (J _c) and irreversibility field (H _irr). Recently, we have shown that repagermanium (C₆H₁₀Ge₂O₇) is an effective additive, enhancing both J _c and H _irr. To look into details of the processes taking place during the reactive sintering, a thermal analysis study (0.167 K s^?1, in Ar) is reported. We used differential scanning calorimetry between 298 and 863 K and simultaneous thermogravimetric—differential thermal analysis between 298 and 1233 K. Samples were mixtures of powders with composition 97 mol% MgB₂ and 3 mol% C₆H₁₀Ge₂O₇. Up to 863 K, repagermanium decomposes by multiple steps and forms amorphous phases. A reaction with MgB₂ is not observed. Above this temperature, partial decomposition of MgB₂ occurs. Crystalline Ge and MgO are detected before formation of Mg₂Ge and MgB₄, when temperature approaches the melting point of Ge (1211 K). Carbon substitution for boron in the crystal lattice of MgB₂ is observed for samples heated above 863 K. The amount of substitutional C does not significantly change with temperature.     

Transition-metal mediated heteroatom removal by reactions of FeL+ [L=O,C4H6, c-C5H6, c-C5H5, C6H6, C5H4(=CH2)] with furan,thiophene, and pyrrole in the gas phase

Reactions of Fe⁺ and FeL⁺ [L=O, C₄H₆, c-C₅H₆, C₅H₅, C₆H₆, C₅H₄(=CH₂)] with thiophene, furan, and pyrrole in the gas phase by using Fourier transform mass spectrometry are described. Fe⁺, Fe(C₅H₅)⁺, and FeC₆H ₆ ⁺ yield exclusive rapid adduct formation with thiophene, furan, and pyrrole. In addition, the iron-diene complexes [FeC₄H ₆ ⁺ and Fe(c-C₅H₆)⁺], as well as FeC₅H₄(=CH₂)⁺ and FeO⁺, are quite reactive. The most intriguing reaction is the predominant direct extrusion of CO from furan by FeC₄H₆ ⁺, Fe(c-C₅H₆)⁺, and FeC₅H₄(=CH₂)⁺. In addition, FeC₄H ₆ ⁺ and Fe(c-C₅H₆)⁺ cause minor amounts of HCN extrusion from pyrrole. Mechanisms are presented for these CO and HCN extrusion reactions. The absence of CS elimination from thiophene may be due to the higher energy requirements than those for CO extrusion from furan or HCN extrusion from pyrrole. The dominant reaction channel for reaction of Fe(c-C₅H₆)⁺ with pyrrole and thiophene is hydrogen-atom displacement, which implies D^O(Fa(N₅H₅)⁺-C₄H₄X)>D^O(Fe(C₅H₅)⁺-H)=46±5 kcal mol^?1. D^O(Fe⁺-C₄H₄S) and D^O(Fe⁺-C₄H₅N)=D^O(Fe⁺-C₄H₆)=48±5 kcal mol^?1. Finally, 55±5 kcal mol^?1=D^O(Fe⁺-C₆H₆)>D^O(Fe⁺-C₄H₄O)>D^O(Fe⁺-C₂H₄)=39.9±1.4 kcal mol^?1. FeO⁺ reacts rapidly with thiophene, furan, and pyrrole to yield initial loss of CO followed by additional neutral losses. D^O(Fe⁺-CS)>D^O(Fe⁺-C₄H₄S)≈48±5 kcal mol^?1 and D^O(Fe⁺-C₄H₅N)≈48±5 kcal mol^?1>D^O(Fe⁺-HCN)>D^O(Fe⁺-C₂H₄)=39.9±1.4 kcal mil^?1.     

Highly enhanced in-field critical current density of MgB2 superconductor by combined addition of burned rice husk and nano Ho2O3

With the aim of improving flux pinning and in-field critical current density [J_C(H)], two physically and chemically different additives – burned rice husk (BRH) and nano Ho₂O₃ were introduced into in situ MgB₂ superconductor. The effects of the above two additives were studied individually and combinedly. Ho₂O₃ decomposed and reacted with B to form HoB₄, without any substitution. BRH caused considerable amount of C substitution at B site and formed Mg₂Si and Mg₂C₃ secondary phases. Addition of Ho₂O₃ improved the J_C(H) only marginally, but BRH improved the J_C(H) strongly. Combined addition of Ho₂O₃ with BRH was found to be much more effective than their solo addition for the enhancement of J_C(H) of MgB₂.     

Fragmentation reactions ofN-sulfinylaniline PhNSO by the dinuclear complex [Fe2(CO)7{μ-C(R)C(NEt2)}]: Nitrene and sulfur insertions into iron carbene bonds. Synthesis and x-ray structures of [Fe2(CO)6{μ-N(Ph)C(NEt2)C(Me)S}] [Fe2(CO)6{μ-N(Ph)C(NEt2)C(Ph)S}] · 0.5C6H14 and [Fe2(CO)6{μ-C(C3H5)C(NEt2)N(Ph)SO}] · 0.5CH2Cl2

The diiron ynamine complexes [Fe₂(CO)₇{μ-C(R)C(NEt₂)}] (1) (R=Me, Ph, C₃H₅, SiMe₃) react with theN-sulfinylaniline, PhNSO, in refluxing hexane to yield the complexes [Fe₂(CO)₆{μ-N(Ph)C(Me)S}] (2), [Fe₂(CO)₆{μ-N(Ph)C(NEt₂)C(Ph)S}] · 0.5C₆H₁₂ (3), [Fe₂(CO)₆{μ-C(C₃H₅)C(NEt₂)N(Ph)SO}] · 0.5CH₂Cl₂ (4), and [Fe₂(CO)₆{μ-C(SiMe₃)C(NEt₂)S)}] (5). Compound 5 was found to be identical to the previously reported product obtained from the reaction of 1 with sulfur. Compounds 2, 3, and 4 were characterized by single crystal X-ray diffraction analyses. Crystal data: for 2: space group = P2₁/n,a=9.533(1) Å,b=18.830(4) Å,c=12.705(4) Å, β=107.01(2)°,Z=4, 2687 reflections,R=0.027; for 3: space group=P2₁/n,a=13.660(2) Å,b=19.096(8) Å,c=10.972(2) Å, β=90.62(1)°,Z=4, 2821 reflections,R=0.036; for 4: space group=P2₁/a,a=18.098(5) Å,b=16.564(4) Å,c=18.548(2) Å, β=115.44(2)°,Z=4, 3569 reflections,R=0.041. Complexes 2 and 3 result from fragmentation of theN-sulfinylaniline ligand and insertion of the nitrene grouping into the Fe=C(aminocarbene) bond, whereas the sulfur atom inserts into one Fe-C bond of the bridging carbene. Compound 4 is formed by insertion of the entireN-sulfinyl aniline ligand into the Fe=C(aminocarbene) bond. All three complexes have basket-like arachno structure isolobal to the benzvalene one.     

The dimeric unit [La(H2O)4(m-PO3C6H4COOH)(m-PO2(OH)C6H4COOH)(m-PO(OH)2C6H4COOH)]2 as building block of layered hybrid material

A new hybrid organic–inorganic material with the structural formula unit [La(H₂O)₄(m-PO₃C₆H₄COOH)(m-PO₂(OH)C₆H₄COOH)(m-PO(OH)₂C₆H₄COOH)]₂ (or [La(H₂O)₄C₂₁H₁₈O₁₅P₃]₂) has been synthesized under hydrothermal condition from La(NO₃)₃·6H₂O and 3-phosphonobenzoic acid (m-PO(OH)₂–C₆H₄–COOH) which is a rigid organic precursor possessing two types of functional groups: phosphonic acid and carboxylic acid. The two units of the produced hybrid are linked together by hydrogen bonds leading to a layered framework composing of by a repetition of inorganic and organic slices. The organic layers consist of dimeric units made of two meta-phosphono-benzoic acid linked together by hydrogen bonds involving their COOH groups. Two kinds of dimeric units are observed: PO₃C₆H₄COOH?HOOCC₆H₄PO(OH)₂, present 2 times in the structure, and PO₂(OH)C6H4COOH?HOOCC₆H₄PO₂(OH). The material crystallises in a monoclinic cell (C2/c (15) space group) with the following parameters: a = 42.515(4) Å, b = 7.4378(6) Å, c = 20.307(2) Å, β = 118.031(6)°, V = 5668.2(9) Å³, Z = 4, density = 1.908 g/cm³.     

Hydrothermal synthesis, crystal structure, and magnetic properties of a novel organo-templated iron(III) borophosphate: (C3H12N2)Fe 6(H2O)4[B4P8O32(OH)8]

The organo-templated iron(III) borophosphate (C₃H₁₂N₂)Fe^III ₆(H₂O)₄[B₄P₈O₃₂(OH)₈] was prepared under mild hydrothermal conditions (at 443 K) and the crystal structure was determined from single crystal X-ray data at 295 K (monoclinic, P2₁/c (No. 14), a=5.014(2) Å, b=9.309(2) Å, c=20.923(7) Å, β=110.29(2)°, V=915.9(5) Å³, Z=2, R1=0.049, wR2=0.107 for all data, 2234 observed reflections with I>2σ(I)). The title compound contains a complex inorganic framework of borophosphate trimers [BP₂O₈(OH)₂]⁵⁻ together with FeO₄(OH)(H₂O)- and FeO₄(OH)₂-octahedra forming channels with ten-membered ring apertures in which the diaminopropane cations are located. The magnetization measurements confirm the Fe(III)-state and show an antiferromagnetic ordering at T_N≈14.0(1) K.     

Measurement of barriers to aryl rotation in Cp(CO)2FeCHC6H5+ and Cp(CO)2FeCH(p-CH3C6H4)+

The first observation of barriers to rotation about the C_arylC_carbene bonds in aryl-substituted metal carbene complexes is reported. Using variable temperature ¹H NMR, barriers of 9.1 and 10.4 kcal/mol have been determined for Cp(CO)₂FeCHC₆H₅⁺ and Cp(CO)₂FeCH(p-CH₃C₆H₄)⁺, respectively. The data clearly indicate a geometry of the complex in which the aryl ring lies coplanar with FeC_carbeneC_ipso plane.     

The chemistry and the stereochemistry of poly(N-alkyliminoalanes) : XVI. The crystal and molecular structure of the compound [HAlNCH(CH3)C6H5]6·13 C6H14

The crystal structure of [HAlNCH(CH₃)C₆H₅] ₆·$\text{1}\text{3}$ C₆H₁₄ has been determined by single crystal three-dimensional X-ray analysis. Block-matrix least-squares refinement led to conventional R factor of 0.08. The molecule is built up of a prismatic hexagonal framework, (AlN)₆. Average AlN distances are 1.893(6) and 1.981(7) Å in the six-membered rings and in transverse bonds, respectively. Crystal data: hexagonal, space group P6₃, a 22.296(5), c 18.144(4) Å, V 7811.2 ų, Z = 6, D_c 1.16 g cm^?3.     

Kristall- und molekülstruktur von nonacarbonyl-bis(μ3-phenylarsiniden)trieisen(2FeFe)

Nonacarbonylbis(μ₃-phenylarsinidene)triiron(2FeFe) has been prepared by reaction of Na₂[Fe(CO)₄] with C₆H₅AsCl₂. Its X-ray structural study reveals an Fe₃As₂ cluster. Three Fe(CO)₃ groups occupy the equatorial positions of a distorted trigonal bipyramid with two μ₃-bridging AsC₆H₅ groups at the axial sites. The Fe₃ triangle contains only two FeFe bonds as reflected by different atomic distances.Crystal data: space group P2₁/c, a = 11.427(9), b = 15.43(1), c = 14.60(1) Å, β = 107.32(3)°, Z = 4. With 3786 reflections, for which F_o > 3(F_o), the structure has been refined anisotropically (hydrogen atoms isotropically) to R = 0.048.     

Group IB organometallic chemistry : XXXVII. Complex forming reactions of polynuclear arylcopper compounds: CalkP bond cleavage in 1,2-bis(diphenylphosphino)ethane (diphos) by (2-Me2NCH2C6H4)4Cu4 and crystal structure of [(C6H5)2PCu · diphos]2 · 2 C6H6

Molecular weight measurements and microwave titrations indicate that no interaction occurs between tetrameric 2-Me₂NCH₂C₆H₄Cu (Ar₄Cu₄) and the monodentate ligands PPh₃, CH₃CN or pyridine. However, the tetrameric structure Ar₄Cu₄ breaks down upon interaction (1/1 molar ratio ArCu/L) with the bidentate ligands (L) Diphos or cis-DPPEE to give the monomeric 1/1 complexes ArCu · L.Addition of Diphos to ArCu · Diphos or conducting the reaction of Ar₄Cu₄ with Diphos in a 1/2 ratio (ArCu/Diphos) gives rise to a C_alkP bond cleavage reaction resulting in the formation of dimeric (Ph₂PCu · Diphos)₂ · 2 C₆H₆, ArH and Ph₂PCHCH₂.The molecular structure of (Ph₂PCu · Diphos)₂ · 2 C₆H₆, has been determined by a single-crystal X-ray diffraction study. Crystals are monoclinic, space group P2₁/c and have Z  2 in a unit cell of dimensions a  12.997(6), b  12.669(7), c  22.839(9) Å and β  94.48(4)°. The structure was refined to R  0.048 for 3048 independent reflections. The four copper atoms in the dimer are held together by two Ph₂P bridges. The bonding in the dimer is discussed.     

Effect of Sr-for-Ba isovalent substitution on the local structure, hole distribution and magnetic irreversibility of Cu(Ba,Sr)2YbCu2O6.95(2)

The effect of Sr^II-for-Ba^II isovalent substitution on the magnetic irreversibility field (H_irr) of Cu(Ba_1−ySr_y)₂YbCu₂O_6.95(2) (Cu-1212) sample series (y=0-0.4) is studied to reveal guiding rules for tailoring the intrinsic H_irr characteristics of high-T_c superconductors. It has been assumed that substitution of the larger alkaline-earth cation, Ba^II, by the smaller, Sr^II, might improve the H_irr characteristics as a consequence of the decrease in the thickness of nonsuperconductive blocking block (BB). However, results of the present work show that Sr substitution rather depresses the H_irr characteristics of the Cu-1212-phase superconductors even though the thickness of BB decreases. Both the amount of excess oxygen and the overall positive charge are confirmed to remain constant upon the Sr substitution by wet-chemical and X-ray absorption near-edge structure analyses, respectively. However, from neutron diffraction data analysis, it is found that Sr substitution breaks the conductive CuO chains in BB by shifting part of the excess oxygen atoms from the characteristic b-axis lattice site to the a-axis site. This is believed to decrease the concentration of mobile holes in the BB, as supported by the results of TEP measurements. The lower H_irr(T) lines of the Sr-substituted samples may thus be attributed to the lower concentration of mobile holes in BB.     

Oxyfluorinated compounds with an open structure XVI. Synthesis,structure determination and magnetic properties of Fe4F3(PO4)(HPO4)4(H2O)4(N2C3H12) [ULM-15]

Fe₄F₃(PO₄)(HPO₄)₄(H₂O)₄(N₂C₃H₁₂) (labelled ULM-15) was prepared hydrothermally (7 days, 453 K, autogenous pressure) in the presence of 1,3-diaminopropane as organic template. Its structure was determined by single crystal X-ray diffraction. ULM-15 is monoclinic (Space group C2/c (no 15)) with lattice parameters a = 24.176(1) , b = 14.558(1) , c = 7.186(1) , β = 102.3(1)°, V = 2470.8(3) ³, Z = 4. Its three-dimensional framework is constituted from corner-sharing FeX₆ (X = O, F, H₂O) octahedra and tetrahedral PO₄ and HPO₄ groups. The structure presents trans-chains of FeO₄F₂ octahedra related to ferric dimers [Fe₂O₈F₂(H₂O)₂] by tetrahedral units. They delimit 16-membered rings channels along [001] in which the diprotonated amines are inserted. ULM-15 shows 3D antiferromagnetic behaviour below T_N ≈ 22 K.     

Neue Synthesen und Kristallstrukturen von Bis(fluorphenyl)quecksilber,Hg(Rf)2 (Rf = C6F5, 2, 3, 4, 6‐F4C6H, 2, 3, 5, 6‐F4C6H, 2, 4, 6‐F3C6H2, 2, 6‐F2C6H3)

New Syntheses and Crystal Structures of Bis(fluorophenyl) Mercury, Hg(R_f)₂ (R_f = C₆F₅, 2, 3, 4, 6‐F₄C₆H, 2, 3, 5, 6‐F₄C₆H, 2, 4, 6‐F₃C₆H₂, 2, 6‐F₂C₆H₃) Bis(fluorophenyl) mercury compounds, Hg(R_f)₂ (R_f = C₆F₅, C₆HF₄, C₆H₂F₃, C₆H₃F₂), are prepared in good yields by the reactions of HgF₂ with Me₃SiR_f. The crystal structures of Hg(2, 3, 4, 6‐F₄C₆H)₂ (monoclinic, P2₁/n), Hg(2, 3, 5, 6‐F₄C₆H)₂ (monoclinic, C2/m), Hg(2, 4, 6‐F₃C₆H₂)₂ (monoclinic, P2₁/c) and Hg(2, 6‐F₂C₆H₃)₂ (triclinic, P1) are described.     

Fe(II) and Co(II) pyridinebisimine complexes bearing different substituents on ortho- and para-position of imines: synthesis, characterization and behavior of ethylene polymerization

A series of 2,6-bis(imino)pyridyl iron(II) and cobalt(II) complexes [2,6-(ArNCMe)₂C₅H₃N]MCl₂ (Ar = 2,6-i-Pr₂C₆H₃, M = Fe: 3a, M = Co: 4a; Ar = 2,4,6-i-Pr₃C₆H₂, M = Fe: 3b, M = Co: 4b; Ar = 2,6-i-Pr₂-4-BrC₆H₂, M = Fe: 3c, M = Co: 4c; Ar = 2,4-i-Pr₂-6-BrC₆H₂, M = Fe: 3d, M = Co: 4d) has been synthesized, characterized, and investigated as precatalysts for the polymerization of ethylene in the presence of modified methylaluminoxane (MMAO). The substituents of pyridinebisimine ligands and their positions located significantly influence catalyst activity and polymer property. It is found that the catalytic activities of the iron complexes/MMAO systems are mainly dominated by electronical effect, while those of the cobalt complexes/MMAO systems are primarily controlled by hindering effect.     

Crystal and molecular structure of (μ-p-CH3C6H4C2S) (μ-n-C3H7S)Fe2(CO)6Co2(CO)6

The crystal and molecular structure of the complex containing cobalt-carbon and iron-sulfur cluster cores, (μ-p-CH₃C₆H₄C₂S) (μ-n-C₃H₇S)Fe₂(CO)₆Co₂(CO)₆, has been determined by X-ray diffraction method. The crystals are triclinic, space group P&1bar;, with a — 9.139(2), b=9.610(1), c-17.183(2) Å, α = 84.36(1), β-89.45(1), γ=88.15(1)°, V-1501.0 ų; Z=2, D_c=1.74 g/cm³. R=0.072, Rw=0.081. The results of the structure determination show a cobalt-carbon cluster core formed through the reaction of (μ-p-CH₃C₆H₄C₂S)(μ-n-C₃H₇S)Fe₂(CO)₆ with Co₂(CO)₈. In the cobalt-carbon cluster core, the bond length of the original C≡C lengthened to 1.324 Å which is close to the typical value of carbon-carbon double bond. The groups connecting the carbons of the cluster core are in cis position and lie on the opposite side of cobalt atoms. In this complex, the conformation of —SC₃H₇ is e-type, while that of —SC₂C₆H₄CH₃ is a-type.     

Darstellung und eigenschaften von und reaktionen mit metallhaltigen heterocyclen: XXXIII. Synthese und kristallstruktur von (μ3-thio)(μ3-organophosphido)tris(tricarbonyleisen)-(2Fe-Fe)-komplexen

The cluster compounds (μ₃-S)(μ₃-PR)Fe₃(CO)₉ are obtained by reaction of the dichloroorganylphosphane sulphides RP(S)Cl₂ (R = CH₃, 4-CH₃OC₆H₄, C₆H₅) with Na₂[Fe(CO)₄] in ether under cleavage of the PS bond. On the basis of X-ray crystallographic determinations the iron clusters crystallize for R = 4-CH₃OC₆H₄ and C₆H₅ in the monoclinic and triclinic space group C2/c and P$\text{1}$ with Z = 8 and 4, respectively.     

m -Terphenyl derivative of titanium(III): Cp2TiR (Cp=C5H5; R =2,6-(4-MeC6H4)2C6H3)

The title compound, Cp₂TiR (Cp=C₅H₅; R=2,6-(4-MeC₆H₄)₂C₆H₃), 1, was prepared by reaction of RLi with [Cp₂TiCl]₂. Compound 1 was characterized by elemental analysis, EPR, and single crystal X-ray crystallography. The title compound crystallizes in the monoclinic space group C2/c with the following unit cell dimensions: a=11.1466(7) Å, b=16.4429(11) Å, c=13.0786(8) Å; b=106.2040(10)^°;V=2301.9(3) ų. The EPR spectrum of 1 displays two signals, a high field signal at g=1.979 and a lower field signal at g=1.959. Significantly, 1 is a sterically encumbered m-terphenyl-stabilized trivalent titanocene paramagnetic complex and may be a practical one-electron reducing reagent.     

Cyclopentadienyleisen-komplexe mit P(OR)3-liganden; Synthese und spektroskopische charakterisierung

Reactions of reactive cyclopentadienyliron complexes C₅H₅Fe(CO)₂I, [C₅H₅Fe(CO)₂THF]BF₄, [C₅H₅Fe(CO)((CH₃)₂S)₂]BF₄ and [C₅H₅Fe(p-(CH₃)₂C₆H₄)]PF₆ with P(OR)₃ as ligands (R = CH₃, C₂H₅, i-C₃H₇ and C₆H₅) lead to the formation of the complex compounds C₅H₅Fe(CO)_2?n(P(OR)₃)_nI and [C₅H₅Fe(CO)_3?n(P(OR)₃)_n]X (n = 1, 2 and n = 1–3, X = BF₄, PF₆). Spectroscopic investigations (IR, ¹H, ¹³C and ³¹P NMR) indicate an increase of electron density on the central metal with increasing substitution of CO groups by P(OR)₃ ligands. The stability of the compounds increase in the same way.     

Synthesis and structural characterization of acetatobis(triphenylphosphine)dicarbonylmanganese(I), (CH3CO2)Mn(CO)2[P(C6H5)3]2: An organometallic complex containing a chelating acetate ligand

The accidental but intriguing synthesis of acetatobis(triphenylphosphine)dicarbonylmanganese(I), (CH₃CO₂)Mn(CO)₂[P(C₆H₅)₃]₂, has been accomplished by the reaction of NaMn(CO)₅ with (CH₃)₃SiCl followed by the addition of triphenylphosphine and acetic acid. A three-dimensional single-crystal X-ray diffraction analysis has shown an octahedral-like molecule containing a symmetrically oxygen-chelating acetate group, the first such group to be reported in a metal carbonyl complex. The two triphenylphosphine ligands occupy mutually trans positions with the two carbonyl ligands possessing the remaining cis sites in the octahedral complex. The compound crystallizes with four molecules in a monoclinic unit cell of space group symmetry $\text{P}\text{2}{}_1\text{c}$ and of dimensions a = 17.744(2) Å, b = 9.692(1) Å, c = 20.004(2) Å, and β = 106.195(4)°. The relatively long MnO(acetate) bond lengths [2.066(6) and 2.069(7) Å] and the relatively short MnCO bond lengths [1.701(12) and 1.760(13) Å] and the relatively short MnP(C₆H₅)₃ bond lengths [2.260(3) and 2.275(3) Å], compared to the corresponding MnCO and MnP(C₆H₅)₃ bond lengths in other manganese carbonyl triphenylphosphine complexes, are rationalized on the basis that the acetate ligand in this molecule functions primarily as a σ-donor.     

Recent advances in synthesis and analysis of Fe(VI) cathodes: solution phase and solid-state Fe(VI) syntheses,reversible thin-film Fe(VI) synthesis,coating-stabilized Fe(VI) synthesis,and Fe(VI) analytical methodologies

Fe(VI) batteries based on unusual ferrate cathodic charge storage have been studied for quite a few years. So far, a class of Fe(VI) compounds have been successfully synthesized and studied as the cathodic materials in both alkaline and nonaqueous battery systems. This paper provides a summary of the syntheses of a range of Fe(VI) cathodes including the alkali Fe(VI) salts Li₂FeO₄, K _x Na_(2?x)FeO₄, K₂FeO₄, Rb₂FeO₄, Cs₂FeO₄, as well as alkali earth Fe(VI) salts CaFeO₄, SrFeO₄, BaFeO₄, and a transition metal Fe(VI) salt Ag₂FeO₄. Two synthesis routes summarized in this paper are the solution phase synthesis and the solid-state synthesis. Preparation of coating-stabilized (coated with KMnO₄, SiO₂, TiO₂, or ZrO₂) Fe(VI) cathodes and preparation of thin-film reversible Fe(VI/III) cathodes are also presented. Fe(VI) analytical methodologies summarized in this paper include Fourier transform infrared spectrometry, titrimetric (chromite), ultraviolet-visible spectroscopy, X-ray diffraction, inductively coupled plasma spectroscopy, Mössbauer spectrometry, potentiometric, galvanostatic, and cyclic voltammetry. Cathodic charge transfer of Fe(VI) is also briefly presented.