Strukturchemische Untersuchungen von Monammin-Kupfer(I)-Komplexen: [CuNH3]2[Pt(CN)6], [CuNH3]2[Pt(CN)4] und Cu3[Co(CN)6]-2 NH3

Structurally Chemical Investigation of Monoammin Copper (I) Complexes : [CuNH₃]₂[Pt(CN)₆], [CuNH₃]₂[Pt(CN)₄] and Cu₃[Co(CN)₆] · 2NH₃ The preparation and the properties of [CuNH₃]₂[Pt(CN)₆], [CuNH₃]₂[Pt(CN)₄] and Cu₃[Co(CN)₆] · 2NH₃ are described. I.R. and Raman spectra have been recorded and assigned. According to X-ray powder diagrams, [CuNH₃]₂[Pt(CN)₆] crystallizes in the trigonal space group D–P3 ml, a = 7.771, c = 5.988 Å, Z = 1. According to the spectroscopic and crystallographic data, it is concluded that the Cu_I ion is coordinated with one NH₃ group and with the N atoms of the cyanometallate anions. The coordination number of the Cu⁺ is 4 in [CuNH₃]₂[Pt(CN)₆] and 3 in [CuNH₃]₂[Pt(CN)₄]. In the Cu₃[Co(CN)₆] · 2 NH₃ complex two Cu atoms have the coordination number 2, the third Cu atom 4.     

Über die Kristallstrukturen der Cyanokomplexe [Co(NH3)6][Fe(CN)6], [Co(NH3)6]2[Ni(CN)4]3 · 2 H2O und [Cu(en)2][Ni(CN)4]

On the Crystal Structures of the Cyano Complexes [Co(NH₃)₆][Fe(CN)₆], [Co(NH₃)₆]₂[Ni(CN)₄]₃ · 2 H₂O, and [Cu(en)₂][Ni(CN)₄] Of the three title compounds X‐ray structure determinations were performed with single crystals. [Co(NH₃)₆][Fe(CN)₆] (a = 1098.6(6), c = 1084.6(6) pm, R3, Z = 3) crystallizes with the CsCl‐like [Co(NH₃)₆][Co(CN)₆] type structure. [Co(NH₃)₆]₂[Ni(CN)₄]₃ · 2 H₂O (a = 805.7(5), b = 855.7(5), c = 1205.3(7) pm, α = 86.32(3), β = 100.13(3), γ = 90.54(3)°, P1, Z = 1) exhibits a related cation lattice, the one cavity of which is occupied by one anion and 2 H₂O, whereas the other contains two anions parallel to each other with distance Ni…Ni: 423,3 pm. For [Cu(en)₂][Ni(CN)₄] (a = 650.5(3), b = 729.0(3), c = 796.5(4) pm, α = 106.67(2), β = 91.46(3), γ = 106.96(2)°, P1, Z = 1) the results of a structure determination published earlier have been confirmed. The compound is weakly paramagnetic and obeys the Curie‐Weiss law in the range T < 100 K. The distances within the complex ions of the compounds investigated (Co–N: 195.7 and 196.4 pm, Ni–C: 186.4 and 186.9 pm, resp.) and their hydrogen bridge relations are discussed.     

Trigonal kristallisierende Metall(II)-hexacyanoferrate(II)M2II[Fe(CN)6]

Trigonal Crystallizing Metal(II) Hexacyanoferrates(II) M₂^II[Fe(CN)₆] According to X-ray powder diagrams, Ca₂[Fe(CN)₆], Cd₂[Fe(CN)₆], Zn₂[Fe(CN)₆] · 2 H₂O, Pb₂[Fe(CN)₆] and the firstly described compounds Zn₂[Fe(CN)₆] · 2 NH₃ and Sn₂[Fe(CN)₆] crystallize trigonal containing one formula unit in the unit cell. Ca₂[Fe(CN)₆] and Cd₂[Fe(CN)₆] are belonging to the space group D—P3 1m, the other compounds to D—P3 m1. The latters are described as coordination polymers with a coordination number 4 for Zn and 3 for Sn and Pb, respectively.     

Preparation of57Fe enriched K4[Fe(CN)6] and K3[Fe(CN)6]

A simple method to prepare⁵⁷Fe enriched K₄[Fe(CN)₆] and K₃[Fe(CN)₆] is described. The yields of the products are much better than those reported in the literature so far. The enrichment is essential for⁵⁷Fe Mössbauer investigation in a variety of Prussiate type complexes and other inorganic compounds which are conveniently prepared from K₄[Fe(CN)₆] and K₃[Fe(CN)₆]. K₄[Fe(CN)₆] was obtained by reacting freshly prepared Fe(OH)₃ with glacial acetic acid and treating with iron acetate in boiling aqueous solution of KCN. The novel feature of the procedure to obtain K₃[Fe(CN)₆] is that the oxidation of K₄[Fe(CN)₆] has been carried out in the solid state by passing chlorine gas over the powdered specimen. K₃[Fe(CN)₆] was crystallised from alkaline solution of this oxidised powder. The compounds were characterised by Mössbauer spectroscopy.     

Die Struktur der Hydrate von Co3[Co(CN)6]2 und Cd3[Co(CN)6]2

The crystal structures of Co₃[Co(CN)₆]₂, 12 H₂O (a, = 10.210 ± 0.005 Å) and Cd₃[Co(CN)₆]₂, 12 H₂O (a = 10.590 ± 0.005 Å) have been determined by X-ray powder methods. According to the measured density the unit cell contains 1 1/3 formula units with 4 Co²⁺ (Cd²⁺) in 4a, 2 2/3 Co³⁺ in 4b, 16 C and 16 N in 24e, 8 H₂O_I near 24e, (96k) and 8 H₂O_II near 8 _c (192 l). Structure factor calculations based on the space group O_h⁵ - F m 3 m lead to the following final values of the reliability index R: 0.038 (Co₃[Co(CN)₆]₂, 12 H₂O) and 0.037 (Cd₃[Co(CN)₆]₂, 12 H₂O). The interatomic distances for the cobaltous compound (in parentheses for the cadmium compound) are: Co³⁺-C: 1.88 Å (1.89); C-N: 1.15 Å (1.17); Co²⁺-N: 2.08 Å (2.24); Co²⁺-O_I: 2.10 Å (2.27); shortest O_I-H-O_II-bonds: 2.89 Å (2.82). Co³⁺ is octahedrally coordinated by six carbon atoms, the divalent metal ion by four nitrogen atoms and two water molecules. The two different metal ions are connected by M²⁺-N-C-Co³-bonds to a threedimensional network. The infrared and electronic spectra are shown to be in agreement with the results of the structure analyses of these compounds. The observed positions of the OH-stretching vibrations lead to a hydrogenbond-length of 2.8–2.95 Å.     

The Representation of Electrical Conductances for Polyvalent Electrolytes by the Quint-Viallard Conductivity Equation. Part 3. Unsymmetrical 3:1, 1:3, 3:2, 4:1, 1:4, 4:2, 2:4, 1:5 1:6 and 6:1 Type Electrolytes. Dilute Aqueous Solutions of Rare Earth Salts, Various Cyanides and other Salts

Electrical conductivities of dilute aqueous solutions for unsymmetrical electrolytes of the type 3:1, 1:3, 3:2, 4:1, 1:4, 4:2, 2:4, 1:5 1:6 and 6:1 are reexamined in the framework of the Quint-Viallard conductivity equations, in order to obtain a uniform representation of their conductivities. The molar and equivalent limiting conductances were evaluated with ion association constants, which were treated as adjustable parameters. The derived values were compared with corresponding results from the literature. The following electrolytes are considered: rare earth (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er) halides, perchlorides, nitrates and sulfates; hexamminecobalt and tris-ethylenediaminecobalt halides, perchlorides, nitrates and sulfates; [Ni₂(trien)₃]Cl₄, [Pt(pn)₃]Cl₄, [Co₂(trien)₃]Cl₆; cyanides K₃[Fe(CN)₆], K₃[Co(CN)₆], M₃[W(CN)₈] with M=Na, K, Rb, Cs; Ca₂[Fe(CN)₆], K₄[Fe(CN)₆], K₄[Mo(CN)₈], K₄[W(CN)₈], K₄[Ru(CN)₈], (Me₄N)₄[Fe(CN)₆], (Pr₄N)₄[Fe(CN)₆], K₄[Mo(CN)₈], (Me₄N)₄[Mo(CN)₈], (Et₄N)₄[Mo(CN)₈] and (Pr₄N)₄[Mo(CN)₈]; phosphates Na₄P₂O₇, Na₄P₄O₁₂, Na₅P₃O₁₀, Na₆P₆O₁₈ and (Me₄N)₄P₄O₁₂.     

Activity coefficients of electrolytes from the emf of liquid membrane cells. III: LaCl3, K3Fe(CN)6, and LaFe(CN)6

The activity coefficients of LaCl₃, K₃Fe(CN)₆, and LaFe(CN)₆ were measured down to about 1×10^–4, 3×10^–5, and 2×10^–5 mol-kg^–1 respectively, by means of cells with ion-exchange liquid membranes. In the diluted region, the trend of lanthanum chloride agrees with the Debye-Huckel theory and corroborates earlier findings in the literature relevant to more concentrated solutions, with minor systematic corrections of the _± values. K₃Fe(CN)₆ attains (rather than tends to attain) the Debye-Huckel limiting slope at1×10^–3 mol-kg^–1, and lanthanum ferricyanide in the diluted region shows negative deviations from the limiting law, similar to the ones predicted for large-sized, highly-charged ions in the diluted region by Bjerrum's, IPBE, and Mayer's theories. The behavior of LaCl₃ in the concentrated solutions proves that lanthanum ion drags along with it into the membrane many molecules of water which were then found to be twelve. Pitzer's theory best-fit coefficients that meet the experimental curves to be reproduced satisfactorily are reported.     

Elektrochemisches Verhalten von Redox-Systemen in Lösungsmittelgemischen, 2. Mitt.: Das System K4[Fe(CN)6]-K3[Fe(CN)6] in Fettsäure-Wasser-Gemischen

Zusammenfassung Es wurden die elektrochemischen Eigenschaften des Redox-Systems K₄[Fe(CN)₆]-K₃[Fe(CN)₆] in Ameisensäure-Wasser-, Essigsäure-Wasser-, Propionsäure-Wasser- und n-Buttersäure-Wasser-Gemischen untersucht. Die Veränderungen des Redoxpotentials, der Leitfähigkeit und der Dielektrizitäts-konstante wurden studiert.Es wurde bewiesen, daß die Potentialveränderung des Redox-Systems bei kleiner Säurekonzentration (n _s<0,6–0,7) vor allem durch die Wasserstoffionen-Konzentration der Lösung bestimmt wird. Mit der Zunahme der H⁺-Konzentration nimmt die Aktivität des [Fe(CN)₆]^4– in größerem Maße ab als die des [Fe(CN)₆]^3–.Bei großer Säurekonzentration beeinflußt dagegen hauptsächlich die Anionsolvatation durch das Lösungsmittelgemisch die Verschiebung des Redoxpotentials. Die Solvatation ruft eine Strukturveränderung hervor, wodurch die Elektronen-population der Lösungsmittelmoleküle in der Nähe der Cyanoferrat-Ionen abnimmt, die Elektronen-Acceptor-Wirkung des Lösungsmittels wächst. Dieser Prozeß bewirkt in bekannter Weise die Zunahme des Redoxpotentials.

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The electrochemical behaviour of redox systems in mixed solvents, II.: TheK ₄[Fe(CN) ₆]-K ₃[Fe(CN) ₆] system in fatty acid-water mixtures

The electrochemical behaviour of the K₄[Fe(CN)₆]-K₃[Fe(CN)₆] system has been investigated in mixtures of water with formic, acetic, propionic and n-butyric acid, resp. The change of the redox potential, the conductivity and the dielectric constant has been studied. It has been proved that the change of the redox potential of the system at low acid concentration (n _s<0.6–0.7) is determined by the H⁺ concentration. Increasing the H⁺ concentration, the activity of the [Fe(CN)₆]^4– decreases in a higher extent than the activity of [Fe(CN)₆]^3–.On the other hand, at high acid concentration the shift in the redox potential is influenced first of all by the anion solvating effect of the solvent. The solvation causes such a change in the structure, that the electron population of the solvent molecules around the [Fe(CN)₆]^4– ions decreases, the acceptor strength of the solvent increases. It is well known that this process causes an increase in the redox potential.

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Mit 7 Abbildungen     

MÖSSBAUER- und Infrarotspektren von Addukten des K4[Fe(CN)6] mit Antimontrihalogeniden

Mössbauer- and IR Spectra from the Addition Compounds of K₄[Fe(CN)₆] with Antimony Trihalides By the reaction of K₄[Fe(CN)₆] with SbX₃ in the melt (X = Cl, Br) or in SO₂ solution (X = F) the addition compounds K₄[Fe(CNSbX₃)₆] (X = F, Cl) and K₄[Fe(CNSbX₃)₄(CN)₂] (X = Cl, Br) are formed. The IR spectra of these compounds have been interpreted. The MÖSSBAUER spectra are single lines which exhibit a slight broadening compared with K₄[Fe(CN)₆] · 3 H₂O. The values of the isomer shifts following the order of the LEWIS acid strengths of the SbX₃ molecules correspond to a small but significant increase of the s-electron density, which is explained by the increasing influence of the π-acceptor function of the ligands.     

Activity coefficients from the emf of liquid membrane cells V. alkaline earth hexacyanoferrates (III) in aqueous solutions at 25°C

The relative mean activity coefficients of the M₃[Fe(CN)₆]₂ salts, M=Mg, Ca, Sr, Ba, are measured down to about 5×10^–6 mol-kg^–1 using the liquid membrane cell method. In the dilute region these salts display negative instead of positive deviations from the limiting law, contrary to Debye-Hückel's theory predictions. An indirect method based on auxiliary emf measurements in MCl₂, K₃Fe(CN)₆ and KCl, rather than a theory-assisted direct extrapolation to zero of the relative activity coefficients, is used to identify the actual values of the activity coefficients. The data are compared with Mayer's theory, ion-pair theory and numerical integration of the Poisson-Boltzmann equation. Best-fit coefficients of Pitzer's equation which meet the activity coefficients of the M₃[Fe(CN)₆]₂ salts to be reproduced, are reported.     

Elektrochemisches Verhalten von Redox-Systemen in Lösungsmittel-Gemischen, 1. Mitt.: Das System K4[Fe(CN)6]—K3[Fe(CN)6] in Gemischen von Wasser mit organischen Lösungsmitteln

Zusammenfassung Das elektrochemische Verhalten des Redoxsystems K₄[Fe(CN)₆]/K₃[Fe(CN)₆] wurde in Methanol-Wasser-, Äthanol-Wasser-, Dioxan-Wasser-, Tetrahydrofuran-Wasser-und Aceton-Wasser-Gemischen in Abhängigkeit von der Zusammensetzung des Lösungsmittels untersucht.Die Veränderungen des Redoxpotentials, der Leitfähigkeit und der Dielektrizitätskonstante wurden studiert, die Absorptionsspektra sowohl der einzelnen Komponenten als auch des Redoxsystems in sichtbaren und UV-Gebiet aufgenommen und ihre zeitliche Stabilität auch in Methanolhaltigen Lösungen festgestellt.Es wurde gezeigt, daß die Veränderung des Redoxpotentials — vor allem — von den, die Solvatation beeinflussenden Koordinationseigenschafte der Lösungsmittel verursacht wird. In den Lösungsmittelgemischen verändern sich die Dissoziationsverhältnisse von K₄[Fe(CN)₆] bzw. K₃[Fe(CN)₆] hauptsächlich infolge der Veränderung der Dielektrizitätskonstanten. Dieser Umstand wirkt indirekt auf das Redoxpotential des Systems.Die verschiedenen Lösungsmittelgemische rufen aber auch unmittelbar durch ihre, die Elektronendichte beeinflussenden Donor- und Acceptor-Eigenschaften die Veränderung des Redoxpotentials hervor.

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The electrochemical behaviour of redox systems in mixed solvents, I: The K₄[Fe(CN)₆]—K₃[Fe(CN)₆] system in organic solvent-water mixtures

The electrochemical behaviour of the K₄[Fe(CN)₆]—K₃[Fe(CN)₆] system has been investigated in methanol-water, ethanol-water, dioxane-water, tetrahydrofuran-water and acetone-water mixtures, as a function of the composition of the solvents.Changes in redox potential, conductivity, and dielectric constants have been investigated. In addition to the above the absorption spectra of the individual components and redox systems have been examined in the ultraviolet and visible range. The stabilities of the spectra have been established as a function of time, also in solvents containing methanol.It has been proved that the change of redox potential is caused-first of all—by the coordination behaviour of the solvent, affecting solvation. In the mixtures of solvents the dissociation properties of K₄[Fe(CN)₆] and K₃[Fe(CN)₆] are changed in consequence of the change in dielectric constants. The redox potential of the system is indirectly affected by this phenomenon.The change of redox potential, however, amy also be directly caused by the different mixtures of solvents, owing to their donor-acceptor properties affecting electron density.

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Mit 9 Abbildungen

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Herrn Prof. Dr.H. Nowotny gewidmet.     

Double complex salts [Ni(NH3)6]3[Fe(CN)6]2 and [Ni(NH3)6]3[Cr(CNS)6]2: Synthesis and properties

The double complex salts [Ni(NH₃)₆]₃[Fe(CN)₆]₂ and [Ni(NH₃)₆]₃[Cr(CNS)₆]₂ were synthesized and their thermal decomposition in air was studied. The values of interplanar distances in crystal lattices were determined. The compounds are proposed as precursors for producing homogeneous bimetallic nanodimensional powders.     

Die Kristallstrukturen von (NH4)2[ReCl6], [ReCl2(CH3CN)4]2[ReCl6] · 2CH3CN und [ReCl4(18-Krone-6)]

The Crystal Structures of (NH₄)₂[ReCl₆], [ReCl₂(CH₃CN)₄]₂[ReCl₆] · 2CH₃CN and [ReCl₄(18)(Crown-6)] Brown single crystals of (NH₄)₂[ReCl₆] are formed by the reaction of NH₄Cl with ReCl₅ in a suspension of diethylether. [ReCl₂(CH₃CN)₄]₂[ReCl₆] · 2CH₃CN crystallizes as brown crystal plates from a solution of ReCl₅ in acetonitrile. Lustrous green single crystals of [ReCl₄(18-crown-6)] are obtained by the reaction of 18-crown-6 with ReCl₅ in a dichloromethane suspension. All rhenium compounds are characterized by IR spectroscopy and by crystal structure determinations. (NH₄)₂[ReCl₆]: Space group Fm3 m, Z = 4, 75 observed unique reflections, R = 0.01. Lattice constant at ?70°C: a = 989.0(1) pm. The compound crystallizes in the (NH₄)₂[PtCl₆] type, the Re? Cl distance is 235.5(1) pm. [ReCl₂(CH₃CN)₄]₂[ReCl₆] · 2CH₃CN: Space group P1, Z = 1, 2459 observed unique reflections, R = 0.12. Lattice dimensions at ?60°C: a = 859.0(1), b = 974.2(7), c = 1287.3(7) pm, α = 102.69(5)°, b? = 105.24(7)°, γ = 102.25(8)°. The structure consists of two symmetry-independent [ReCl₂(CH₃CN)₄]⁺ ions with trans chlorine atoms, [ReCl₆]^2? ions, and included acetonitrile molecules. In the cations the Re? Cl bond lengths are 233 pm in average, in the anion they are 235 pm in average. [ReCl₄(18-crown-6)]: Space group P2₁/n, Z = 4, 3 633 observed unique reflections, R = 0.06. Lattice dimensions at ?70°C: a = 1040.2(4), b = 1794.7(5), c = 1090.0(5) pm, b? = 108.91(4)°. The compound forms a molecular structure, in which the rhenium atom is octahedrally coordinated by the four chlorine atoms and by two oxygen atoms of the crown ether molecule.     

Neues über K2[MnF6], Rb2[MnF6] und Cs2[MnF6]

News on K₂[MnF₆], Rb₂[MnF₆], and Cs₂[MnF₆] Cs₂[MnF₆] (a = 8.97₂ Å) and Rb₂[MnF₆] (a = 8.53₁ Å) as well as this with K₂[MnF₆] (a = 8.22₁ Å and hexagonal a = 5.72₂, c = 9.33₁ Å) form mixed crystals of the K₂PtCl₆ type of structure. Calculations of the Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, lead contrary to former assumptions to distances Mn? F of about 1.86 Å (CN 6).     

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.     

Magnetic Properties of M3[Fe(Cn)6]2Xh2O (M = Co (II), Ni(II), Cu(II), Zn(II))

Compounds of the type M₃[Fe(CN)₆]₂XH₂O (M = Co(II), Ni(II), Cu(II), and Zn(II)) were prepared and magnetic properties of their powders were investigated by means of EPR spectra, Mössbauer effect and magnetic susceptibility measurements. The temperature dependence of the magnetization for the complexes Co₃[Fe(CN)₅]₂- 10H₂O, Ni₃[Fe(CN)₆]₂-10H₂O and Cu₃[Fe(CN)₆]₂-4H₂O revealed that below the critical temperatures 15, 22 and 20 K respectively, these complexes have zero-field magnetization. The magnetic hysteresis at 10 K for Co(II), Ni(II) and Cu(II) complexes was observed. Mössbauer spectra at 4.2 K for the compounds are discussed.     

Hydrate isomerism in [Cu(en)2(H2O)1.935]2[Fe(CN)6]·4H2O

The title compound, bis[di­aqua­bis­(ethyl­enedi­amine‐κ²N,N′)copper(II)­] hexa­cyano­iron(II) tetrahydrate, [Cu(C₂H₈N₂)₂(H₂O)_1.935]₂[Fe(CN)₆]·4H₂O, was crystallized from an aqueous reaction mixture initially containing CuSO₄, K₃[Fe(CN)₆] and ethyl­enedi­amine (en) in a 3:2:6 molar ratio. Its structure is ionic and is built up of two crystallographically different cations, viz. [Cu(en)₂(H₂O)₂]²⁺ and [Cu(en)₂(H₂O)_1.87]²⁺, there being a deficiency of aqua ligands in the latter, [Fe(CN)₆]⁴⁻ anions and disordered solvent water mol­ecules. All the metal atoms lie on centres of inversion. The Cu atom is octahedrally coordinated by two chelate‐bonded en mol­ecules [mean Cu—N = 2.016 (2) Å] in the equatorial plane, and by axial aqua ligands, showing very long distances due to the Jahn–Teller effect [mean Cu—O = 2.611 (2) Å]. In one of the cations, significant underoccupation of the O‐atom site is observed, correlated with the appearance of a non‐coordinated water mol­ecule. This is interpreted as the partial contribution of a hydrate isomer. The [Fe(CN)₆]⁴⁻ anions form quite regular octahedra, with a mean Fe—C distance of 1.913 (2) Å. The dominant intermolecular interactions are cation–anion O—H⋯N hydrogen bonds and these inter­actions form layers parallel to (001).     

Synthesis of Isotope Enriched (CN3H6)2[57Fe(CN)5NO] starting from 57Fe

A high‐yield, mmolar‐scale synthesis of pure guanidinium nitroprusside, (CN₃H₆)₂[⁽⁵⁷⁾Fe(CN)₅NO] (GNP) from iron metal is described. The iron metal contained pieces of 95.3% ⁵⁷Fe together with normal iron so that an isotope enrichment in ⁵⁷Fe of 25% was achieved. Single‐crystals of GNP could be grown in cubic shape and dimensions of about 3 × 4 × 4 mm³. The purity of the GNP product and the intermediates K₄[⁽⁵⁷⁾Fe(CN)₆] · 3 H₂O and Na₂[⁽⁵⁷⁾Fe(CN)₅NO] · 2 H₂O was ascertained by ⁵⁷Fe Mössbauer spectroscopy as well as ¹³C, ¹⁴N and ⁵⁷Fe NMR spectroscopy. The ⁵⁷Fe NMR chemical shift for [⁽⁵⁷⁾Fe(CN)₅NO]^2– in GNP was detected at +2004.0 ppm [vs Fe(CO)₅].     

Local deposition and characterisation of K2Co[Fe(CN)6] and K2Ni[Fe(CN)6] by scanning electrochemical microscopy

Scanning electrochemical microscopy (SECM) is used to form local deposits of different Prussian blue analogs on macroscopic surfaces of gold and glassy carbon. Dissolution of Co and Ni sacrificial ultramicroelectrodes (UMEs) generates divalent cations in the gap between the UME and the macroscopic specimen electrode. Co²⁺ or Ni²⁺ precipitate with [Fe(CN)₆]^4– formed by reduction of [Fe(CN)₆]^3– at the macroelectrode. By moving the UME while generating Co²⁺ or Ni²⁺, lines can be "drawn" with a width of 130 μm. The line width can be adjusted by reagent concentration and translation speed of the UME. Different pulse programs allow the formation of ring-shaped structures. The deposited hexacyanoferrate microstructures show catalytic activity for the reduction of Fe³⁺ which was imaged in the feedback and generation-collection modes of the SECM. Electronic Publication     

Crystal structure of potassium tetramethylammonium hexacyanocobaltate(III) trihydrate: K3(Me4N)3[Co(CN)6]2·3H2O

The structure of K₃(Me₄N)₃[Co(CN)₆]₂·3H₂O has been determined from three-dimensional X-ray diffraction data. The unit cell is formed by parallel layers of cobalt octahedra [CoC₆] and potassium octahedra, [K(1)N₅O(1)], separated byc/2. In each layer both types of octahedra are located alternatively. The [MeN₄]⁺ tetrahedra are located in the cavities between the two layers of octahedra. The crystal structure of this compound is the first example of its type. TMC 2483