Schnelle thermometrische Siliciumbestimmung in Gu?eisen und Stahl

Zusammenfassung Es wurde eine Schnellbestimmung von Silicium in Gußeisen und Stahl mit Hilfe der Direktinjektionsenthalpimetrie ausgearbeitet. Nach Auflösen der Probe und Dehydratation der Kieselsäure mit konzentrierter Perchlorsäure wird das ausgeschiedene Kieselsäurehydrogel abfiltriert, in Kalilauge gelöst und nach dem Ansäuern mit verdünnter Fluorwasserstoffsäure als Reagens versetzt. Die Bildung des Komplexanions [SiF₆]^2– und die gleichzeitig verlaufende Ausfällung des schwerlöslichen K₂ [SiF₆] sind exotherme Reaktionen. Die freigesetzte Wärmemenge, die vom Siliciumgehalt direkt proportional abhängig ist, wird mit Hilfe eines Thermistors in Brückenschaltung gemessen. Ein Digitalanzeigegerät ermöglicht es, den Siliciumgehalt direkt in Prozent abzulesen.

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Rapid thermometric determination of silicon in cast iron and steel

Summary A method for the rapid determination of silicon by direct injection enthalpimetry in steel and cast iron was elaborated. After dissolution of the sample and dehydration of silicic acid in perchloric acid, the separated silicium oxide hydrogel is dissolved in potassium hydroxide solution and after acidifying, hydrofluoric acid reagent is added. Formation of the complex anion [SiF₆]^2– and the simultaneously proceeding precipitation of insoluble K₂SiF₆ are exothermic reactions. The amount of heat released is directly proportional to the silicon content and is measured by a thermistor. Digital display of the Wheatstone bridge millivoltmeter permits to read the Si content in the sample directly in percent.

     

Quantenchemische Modellrechnungen zur Baugruppenwanderung in Hexafluorosilicaten

Quantum Chemical Model Calculations on the Migration of Si? F Groups in Hexafluorosilicates The transport of different Si? F species was simulated using two [SiF₆]^2? octahedra as example. Activation barriers and charge distributions were calculated with the EHT method. Bearing in mind the structure of cubic hexafluorosilicates calculations were carried out on the migration both along an edge and along a (110) face of the elementary cell. At first [SiF₂]²⁺ and SiF₄ groups were removed from an [Si₂F₁₂]^4? unit to produce a surface vacancy. During a second step planar SiF₄ groups were moved to the neighbouring lattice position. A diffusion of planar SiF₄ is favoured, if the electrostatic interaction between moved and fixed fluorine atoms is as small as possible.     

Beiträge zur Chemie der Halogensilan-Addukte. VIII. Darstellung und Eigenschaften der kationischen Bis-2,2′-Bipyridin-Silicium-Komplexe, [SiCl2b[py2]2+ und [SiF2bipy2]2+

Contributions to the Chemistry of Halogenosilane Adducts. VIII. Preparation and Properties of the Cationic Bis-2,2′-Bipyridinesilicon Complexes, [SiCl₂bipy₂]²⁺ and [SiF₂bipy₂]²⁺ The reactions of SiCl₂bipy₂ (green isomer) and SiF₂bipy₂ with chlorine yield the new ionic complexes of Si, [SiX₂bipy₂]Cl₂ (X = Cl, F). Bromine and iodine react similarly. With these reagents, however, formation of insoluble polyhalides of the complex cations inevitably occurs rendering further investigations difficult. The compounds contain the cis-octahedral cation [SiX₂bipy₂]²⁺. They are soluble in methanol and water and are unusually stable in these solvents. [SiCl₂bipy₂]Cl₂ starts to react observably with methanol (substitution of SiCl) only after weeks. Thus reactions may be performed in this solvent. It follows from the investigation that the green isomer of SiCl₂bipy₂ is a cis-octahedral molecular complex of silicon. Two other green isomers of SiCl₂bipy₂ are shown to exist. The reactions of chlorine with these isomers yield products different from the cis-octahedral complex reported above. Ion-exchange and metathetical reactions of [SiCl₂bipy₂]Cl₂ yield the new compounds [SiCl₂bipy₂]X₂ (X = Br^?, J^?, NO₃^?, ClO₄^?, [Cr(NH₃)₂(NCS)₄]^?, PtCl₆^2?/2). All compounds contain the [SiCl₂bipy₂]²⁺-cation which is investigated in detail (¹H-, ²⁹Si-NMR, IR, UV, ESCA, conductivity, molecular weight). The use of AgF for the synthesis of ionic SiF-complexes (X = F) gives rise to more complicated reactions.     

EPR of Mn2+-doped single crystals of [Co(H2O)6]XY6 (X = Si,Sn, Pt; Y = F,Cl)

EPR studies have been carried out in Mn²⁺-doped paramagnetic single crystals of [Co(H₂O)₆]SiF₆, [Co(H₂O)₆]SnF₆ and [Co(H₂O)₆]PtCl₆ at different temperatures using X-band microwave frequency. Reasonably sharp resonance lines of Mn²⁺ have been obtained at room temperature and analysed using the spin Hamiltonian for trigonal symmetry. From the observed linewidths of Mn^{2 +} in single-crystal [Co(H₂O)₆]SiF₆ the T₁ of Co^{2 +} has been estimated to be = 3.3 × 10⁻¹¹ s. A st phase transition in [Co(H₂O)₆]SiF₆ was observed and the low-temperature phase studied.     

Hexafluorosilicates of 2-substituted anilinium derivatives

The reaction of 45% fluorosilicic acid with methanol solutions of several 2-substituted anilines(L) gave hexafluorosilicates (LH)₂SiF₆. The products were studied by elemental analysis, IR spectroscopy, mass spectrometry, and thermogravimetry. The solubility and the hydrolytic stability of the salts were estimated. The structure of the complex [CH₃O(O)CC₆H₄NH₃]₂SiF₆ was determined by single-crystal X-ray diffraction. The ionic structure is composed of centrosymmetric SiF ₆ ^2? anions (the average Si-F bond length is 1.679(1) Å) and the [CH₃O(O)CC₆H₄NH₃]⁺ cations. The NH ₃ ⁺ group is the donor for the inner-cation H-bond with the carbonyl oxygen atom (NH···O), and for two ion-ion H-bonds (NH···F). The Si-F bond lengths correlate with the strengths of the H-bonds involving the corresponding fluorine atoms.     

Neue Substitutions-Verbindungen des K3[Cr(NCS)6] mit tertiären Phosphinen

New Substitution Compounds of K₃[Cr(NCS)₆] with Tertiary Phosphines . New substitution reactions of K₃[Cr(NCS)₆] with mixed tertiary phophines in n-butanol were carried out. The formulae of the new anions: [Cr(NCS)₄(diethyl-phenylphosphine)₂]^? and [Cr(NCS)₄(diethyl-p-tolyl-phosphine)₂]^? were established by preparation of 30 new derivatives with the hydrochlorides of some organic N-bases, metals, and metal(III) ammines. Electronic and i.r. spectral data are communicated.     

K⋅⋅⋅F/O Interactions Bridge Copper(I) Fluorinated Alkoxide Complexes and Facilitate Dioxygen Activation

Seven E[Cu(OR)₂] copper(I) complexes (E=K⁺, {K(18C6)}⁺ (18C6=[18]crown‐6), or Ph₄P⁺; R=C₄F₉, CPhMe^F₂, and CMeMe^F₂) have been prepared and their reactivity with O₂ studied. The K[Cu(OR)₂] species react with O₂ in a copper‐concentration‐dependent manner such that 2:1 and 3:1 Cu/O₂ adducts are observed manometrically at ?78 °C. Analogous reactivity with O₂ is not observed with the {K(18C6)}⁺ or Ph₄P⁺ derivatives. Solution conductivity data demonstrate that these K[Cu(OR)₂] complexes do not behave as 1:1 electrolytes in solution. The K⁺ ions induce aggregation of multiple [Cu(OR)₂]^? units through K???F/O interactions and thereby effect irreversible O₂ reduction by multiple Cu centers. Bond valence analyses for the potassium cations confirm the dominance of the fluorine interactions in the coordination spheres of K⁺ ions. Intramolecular hydroxylation of ligand aryl and alkyl C? H bonds is observed. Nucleophilic reactivity with CO₂ is observed for the oxygenated Cu complexes and a Cu^II carbonate has been isolated and characterized.     

Molecular Structure of N-Methylbis (2-Hydroxyethyl)Ammonium hexafluorosilicate at 100 and 298 K

Two polymorphic modifications of N-methylbis(2-hydroxyethyl)ammonium hexafluorosilicate (AHFS) crystallize in monoclinic symmetry. The independent part of the unit cell of the low temperature modification contains two cations and an anion. The cell volume is two times smaller in the high temperature modification, the [SiF₆]^2- anion being disordered. In both modifications of methylbis(2-hydroxyethyl)ammonium hexafluorosilicate (HOCH₂CH₂)₂HN⁺[SiF₆]^2-, the [SiF₆]^2- anion and the (HOCH₂CH₂)₂HN⁺CH₃ cation are linked by F…H—O hydrogen bonds. The silicon atom polyhedron in the anion is a tetragonal bipyramid; the coordination polyhedron of the nitrogen atom in the cation is a tetrahedron.     

Syntheses, crystal and electronic structures of three new potassium cadmium(II)/zinc(II) tellurides: K2Cd2Te3, K6CdTe4 and K2ZnTe2

Three new ternary potassium(I) zinc(II) or cadmium(II) tellurides, namely, K₂Cd₂Te₃, K₆CdTe₄ and K₂ZnTe₂, were synthesized by solid-state reactions of the mixture of pure elements of K, Cd (or Zn) and Te in Nb tubes at high temperature. K₂Cd₂Te₃ belongs to a new structure type and its structure contains a novel two-dimensional [Cd₂Te₃]²⁻ layers perpendicular to the b-axis. K(5) cation is located at the center of five member rings of the 2D [Cd₂Te₃]²⁻ layer, whereas other K⁺ cations occupy the interlayer space. K₆CdTe₄ with a K₆HgS₄ type structure features a “zero-dimensional” structure composed of isolated CdTe₄ tetrahedra separated by the K⁺ ions. K₂ZnTe₂ in the K₂ZnO₂ structural type displays 1D [ZnTe₂]²⁻ anionic chains of edge sharing [ZnTe₄] tetrahedra separated by the potassium(I) ions. K₂Cd₂Te₃, K₆CdTe₄ and K₂ZnTe₂ revealed a band gap of 1.93, 2.51 and 3.0 eV, respectively.     

Hydrogen‐bonded frameworks of bis(2‐carboxypyridinium) hexafluorosilicate and bis(2‐carboxyquinolinium) hexafluorosilicate dihydrate

In bis(2‐carboxypyridinium) hexafluorosilicate, 2C₆H₆NO₂⁺·SiF₆²⁻, (I), and bis(2‐carboxyquinolinium) hexafluorosilicate dihydrate, 2C₁₀H₈NO₂⁺·SiF₆²⁻·2H₂O, (II), the Si atoms of the anions reside on crystallographic centres of inversion. Primary inter‐ion interactions in (I) occur via strong N—H...F and O—H...F hydrogen bonds, generating corrugated layers incorporating [SiF₆]²⁻ anions as four‐connected net nodes and organic cations as simple links in between. In (II), a set of strong N—H...F, O—H...O and O—H...F hydrogen bonds, involving water molecules, gives a three‐dimensional heterocoordinated rutile‐like framework that integrates [SiF₆]²⁻ anions as six‐connected and water molecules as three‐connected nodes. The carboxyl groups of the cation are hydrogen bonded to the water molecule [O...O = 2.5533 (13) Å], while the N—H group supports direct bonding to the anion [N...F = 2.7061 (12) Å].     

Beitrage zur chemie des bromtrifluorids 1. Teil pentafluorphenylbrom(III)difluorid und -bis (trifluoracetat)

BrF₃ reacts with C₆F₅SiF₃ to form C₆F₅BrF₂, a volatile, colourless, and thermally stable solid, which melts at 35 – 36 °C without decomposition. Its chemical and spectroscopic properties are in contrast to the product described by Sams [1]. The reactivity of the BrF-bonds in C₆F₅BrF₂ allows displacement of fluorine by groups stable against oxidation. With trifluoroacetic acid anhydride C₆F₅Br[O(O)CCF₃]₂ is formed as the first stable carboxylate of Br(III).     

[Bi4]6– – The Zintl Anion with the Highest Charge per Atom Obtained from Solution

From the dark‐purple solution of the Zintl phase KBi in liquid ammonia dark‐blue crystals of the ammonia solvate K₆[Bi₄](NH₃)₈ were obtained. In contrast to known Bi_n polyanions the chemical bond in the anion [Bi₄]^6– is in accordance with the (8‐N) rule featuring solely Bi–Bi single bonds. [Bi₄]^6– is a butane‐analog valence compound, and with 6 negative charges per 4 atoms it is the anion with the highest known charge per atom obtained from solution. The planarity of the trans‐[Bi₄]^6– unit hints at π orbital contributions of the bismuth atoms. The corresponding reactions of the phases K₅Bi₄ and K₃Bi₂ in liquid ammonia in the presence of [2.2.2]crypt(4, 7, 13, 16, 21, 24‐hexaoxa‐1, 10‐diazabicyclo‐[8.8.8]hexacosane) lead to the salt [K([2.2.2]crypt)]₂[Bi₂](NH₃)₄ with the known electron‐deficient [Bi₂]^2– polyanion and a Bi=Bi double bond.     

Ein neues Oxouranat(VI): K2Li4[UO6]. Mit einer Bemerkung über Rb2Li4[UO6] und Cs2Li4UO6

A New Oxouranate(VI): K₂Li₄[UO₆]. With a Remark about Rb₂Li₄[UO₆] and Cs₂Li₄[UO₆] For the first time K₂Li₄UO₆ has been prepared by an exchange reaction of α-Li₆UO₆ with K₂O [K:U = 2.0:1, sealed au-tube; 750°C; 30 d single crystals; 680°C, 10 d powder]. The irregular shaped single crystals, which are of yellow color and sensitive to moisture crystallize in P3 m1 (Z = 1) with a = 619.27(5), c = 533.76(6) pm. The structure determination (PW 1100, AgKα R = 4.80%, R_w = 4.81% for 220 unique reflexions) reveals a new type of structure. The characteristic elements are the isolated group [UO₆] and the C.N. = 12 for K⁺. While Li(1) has a nearly regular square of 4 O^2? as coordination polyhedron, Li(2) is octahedrally surrounded. The Madelung Part of Lattice Energy (MAPLE) is calculated and discussed. In addition to K₂Li₄[UO₆] the new oxides Rb₂Li₄[UO₆] and Cs₂Li₄[UO₆] are prepared as pale yellow powders which are little sensitive to moisture (both: au-tube, 680°C, 10 d). According to powder datas both compounds are isotypic with K₂Li₄[UO₆] [Rb₂Li₄[UO₆]: a = 622.91(5), c = 535.93(6) pm; Cs₂Li₄[UO₆]: a = 626.70(6), c = 539.92(6) pm].     

Revealing the structural chemistry of the group 12 halide coordination compounds with 2,2′-bipyridine and 1,10-phenanthroline

The coordination compounds of group 12 halides with 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen), 2[CdF₂(bpy)₂]·7H₂O (1), [ZnI(bpy)₂]⁺·I₃^? (2), [CdI₂(bpy)₂] (3), [Cd(SiF₆)H₂O(phen)₂]·[Cd(H₂O)₂(phen)₂]²⁺·F^–·0.5(SiF₆)^2–·9H₂O (4), [Hg(phen)₃]²⁺·(SiF₆)^2–·5H₂O (5), [ZnBr₂(phen)₂] (6), 6[Zn(phen)₃]²⁺·12Br^–·26H₂O (7) and [ZnI(phen)₂]⁺·I^– (8), have been synthesized and characterized by X-ray crystallography, IR spectroscopy, elemental and thermal analysis. Structural investigations revealed that metal?:?ligand stoichiometry in the inner coordination sphere is 1?:?2 or 1?:?3. A diversity of intra- and intermolecular interactions exists in structures of 1–8, including the rare halogen?halogen and halogen?π interactions. The thermal and spectroscopic properties were correlated with the molecular structures of 1–8. Structural review of all currently known coordination compounds of group 12 halides with bpy and phen is presented.     

Zum Einfluß der Gasphase auf die thermische Zersetzung von K2[SiF6]

Effect of the Gas Phase on the Thermal Decomposition of K₂[SiF₆] K₂SiF₆ produced in usual ways is contaminated by traces of oxygen and protons. These and traces of water fed by gas atmosphere influence the thermal decomposition reaction. To study the influence of the gas phase definite amounts of H₂O and HF were added. The formation of SiF₄ was determined. The development of a SiO₂ phase in presence of H₂O and other experimental results suggest the construction of a layer on the K₂SiF₆ surface, which hinders further SiF₄ being developped. Temperature and linear velocity of the gas influence the length of a zone of decomposition migrating through the solid. This is explained by sorption and reaction behavior of intermediately formed fluorosiloxanes.     

Untersuchungen zur Reaktion zwischen Alkalihexafluorosilicaten und einigen oxidischen Niobverbindungen

Investigations of the Reaction between Alkalihexafluorosilicates and Some Oxidic Niobium Compounds The reactions of Na₂SiF₆ with M-Nb₂O₅ or NaNbO₃ always produce Na₂Nb₂O₅F₂ and the thermolysis product is NaNbO₃. On the other hand various reactions of K₂SiF₆. exist. Initially with M-Nb₂O₅ an intermediate phase of a bronzestructure type is formed, like α-K_0,25NbO_2,25F_0,75, being converted into K₃NbO₂F₄ and another amorphous niobium phase. Moreover K₂NbO₃F crystallizes in a long time reaction. However first of all K₂NaNbO₂F₄ is formed by the reaction of K₂SiF₆ with NaNbO₃ and only if there is an excess of K₂SiF₆ this substance is changed slowly into K₃NbO₂F₄. The thermolysis of K₃NbO₂F₄ can produce such compounds as K₆Nb₂O₇F₂.     

Reactivity of Liquid Ammonia Solutions of the Zintl Phase K12Sn17 towards Mesitylcopper(I) and Phosphinegold(I) Chloride

To gain more insight into the reactivity of intermetalloid clusters, the reactivity of the Zintl phase K₁₂Sn₁₇, which contains [Sn₄]^4? and [Sn₉]^4? cluster anions, was investigated. The reaction of K₁₂Sn₁₇ with gold(I) phosphine chloride yielded K₇[(η²‐Sn₄)Au(η²‐Sn₄)](NH₃)₁₆ ( 1 ) and K₁₇[(η²‐Sn₄)Au(η²‐Sn₄)]₂(NH₂)₃(NH₃)₅₂ ( 2 ), which both contain the anion [(Sn₄)Au(Sn₄)]^7? ( 1 a ) that consists of two [Sn₄]^4? tetrahedra linked through a central gold atom. Anion 1 a represents the first binary Au?Sn polyanion. From this reaction, the solvate structure [K([2.2.2]crypt)]₃K[Sn₉](NH₃)₁₈ ( 3 ; [2.2.2]crypt=4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosane) was also obtained. In the analogous reaction of mesitylcopper with K₁₂Sn₁₇ in the presence of [18]crown‐6 in liquid ammonia, crystals of the composition [K([18]crown‐6)]₂[K([18]crown‐6)(MesH)(NH₃)][Cu@Sn₉](thf) ( 4 ) were isolated ([18]crown‐6=1,4,7,10,13,16‐hexaoxacyclooctadiene, MesH=mesitylene, thf=tetrahydrofuran) and featured a [Cu@Sn₉]^3? cluster. A similar reaction with [2.2.2]crypt as a sequestering agent led to the formation of crystals of [K[2.2.2]crypt][MesCuMes] ( 5 ). The cocrystallization of mesitylene in 4 and the presence of [MesCuMes]^? ( 5 a ) in 5 provides strong evidence that the migration of a bare Cu atom into an Sn₉ anion takes place through the release of a Mes^? anion from mesitylcopper, which either migrates to another mesitylcopper to form 5 a or is subsequently protonated to give MesH.     

New Ni–Pt Carbonyl Clusters with a Tetrahedron of Platinum Atoms Encapsulated in an Incomplete Tetrahedron of Nickel Atoms: [Ni36Pt4(CO)45]6− and [Ni37Pt4(CO)46]6−

A fully encapsulated Pt ₄ tetrahedron in an incomplete tetrahedron of 36 nickel atoms is present in [Ni₃₆Pt₄(CO)₄₅]⁶⁻ ( 1 ; see picture for the metal framework), which is obtained as an inseparable mixture with [Ni₃₇Pt₄(CO)₄₆]⁶⁻ ( 2 ) by reaction of [Ni₆(CO)₁₂]²⁻ with K₂[PtCl₄]. The trimethylbenzylammonium salts of 1 and 2 cocrystallize in a 1:1 ratio. The additional Ni atom of 2 caps the truncated vertex of 1 .     

The Binary Group 4 Azides [PPh4]2[Zr(N3)6] and [PPh4]2[Hf(N3)6]

The binary zirconium and hafnium polyazides [PPh₄]₂[M(N₃)₆] (M=Zr, Hf) were obtained in near quantitative yields from the corresponding metal fluorides MF₄ by fluoride–azide exchange reactions with Me₃SiN₃ in the presence of two equivalents of [PPh₄][N₃]. The novel polyazido compounds were characterized by their vibrational spectra and their X‐ray crystal structures. Both anion structures provide experimental evidence for near‐linear M‐N‐N coordination of metal azides. The species [M(N₃)₄], [M(N₃)₅]^? and [M(N₃)₆]^2? (M=Ti, Zr, Hf) were studied by quantum chemical calculations at the electronic structure density functional theory and MP2 levels.     

K5[InSe4] and K12[InS4]2(S): New Alkali Chalcogenido Indates with [InQ4]5– ortho Anions

The new chalcogenido ortho indates(III) K₅[InSe₄] and K₁₂[InS₄]₂(S) were synthesized from melts of the elements (Se) [or with S/In₂S₃ as chalcogen source] at maximum temperatures of 700/800 °C. The two potassium salts, which were characterized by means of X-ray single crystal structure analysis, contain isolated tetrahedral ortho anions [InQ₄]^5–. K₅[InSe₄] crystallizes in a new structure type [monoclinic, space group C2/c, a = 2014.2(2), b = 1553.1(2), c = 1661.1(2) pm, β = 94.716(2)°, Z = 16, R₁ = 0.0317]. The complex structure contains two crystallographically different [InSe₄]^5– tetrahedra [d(In ··· Se) = 254.3–263.6 pm], which are arranged into 4⁴ [In(1), A ] and 3².4.3.4 [In(2), B ] nets. These nets are |: ABA ' B ':| stacked along the a axis. The 11 crystallographically independent K⁺ ions are coordinated by four (1×), five (3×) and six (7×) selenido anions [d(K–Se) = 309–415 pm]. The crystal structure and the calculated electronic structure of the pure ortho indate K₅[InSe₄] are compared with the known “double salts” K₉[InSe₄]₂(Se) and K₉[InSe₄](Se₂)(Se), which exhibit selenide (and diselenide) anions in addition to the ortho metallate. Similarly, the new sulfido indate K₁₁[InS₄]₂(S) contains sulfide anions besides the indate tetrahedra. In the chiral structure (K₆[InTe₄](Cl)-type, hexagonal, space group P6₃mc, a = 1026.22(10), c = 752.34(7) pm, Z = 2, R1 = 0.0332) layers of similarly oriented [InS₄] tetrahedra [d(In ··· Se) = 246.6/248.1 pm] are hexagonally |: AB :| stacked along one threefold axis. The additional sulfide anions are centered in K⁺ octahedra. In contrast to the isotypic chloride, only every second polyhedron within the columns of face-sharing K₆ octahedra is statistically occupied by a sulfide ion. Both of the two different K positions exhibit a sixfold coordination by sulfide anions, with K–S distances between 307.1 and 382.1 pm. In the two title compounds, each of the [InQ₄] tetrahedra is overall enclosed by 18 potassium cations. The crystal chemistry of the new indates is discussed and compared with that of the (yet comparatively low number) of alkali chalcogenido metallates(III) of Fe, Al and Ga containing isolated metallate tetrahedra.