Zur Bestimmung von Aktivierungsparametern für die Stoffübergangs- und Stofftransportprozesse an AgCl- und AgBr-Kristallen mittels radioaktiver Nuklide

A report is given on radiochemical measurements carried out by means of the nuclides ^110mAg⁺, ^82mBr⁻, and ³⁶Cl⁻ in order to determine the activation parameters of the mass transfer processes in AgCl and AgBr in the course of the Ostwald Ripening, examining in particular the influence of the thermal pretreatment and the ageing of the AgCl and AgBr upon the activation parameters. Comparative investigations of the systems AgCl_(s)-^110mAg⁺_(aq) and ^110mAgCl_(s)-Ag⁺_(aq) showed that the mass transfer processes on the crystal (incorporation of the ions into the crystal lattice and detachment of the ions from the lattice points, respectively) as well as the mass transport processes in the crystal lattice (diffusion of the Ag⁺ ions through interstitial sites) can be rate determining, the dehydration of the Ag₊ ions, however, should not be dominant, as has also been proved by measurements in mixed solvents.     

Acoustical properties of single crystals of mercurous halides

Velocities of propagation of elastic waves along principal crystallographic directions in Hg₂Br₂ and Hg₂J₂ single crystals were measured using the pulse and phase-pulse techniques. The values obtained were used to calculate the components of the elastic tensors c_ik and s_ik, as well as the phase and group velocities of propagation of longitudinal and transverse waves in the (100) and (001) planes, and the angular deviation of acoustic energy flux from the direction of the corresponding wave normal. Knowledge of the anisotropy of the elastic properties of Hg₂X₂ crystals and of their change with the anion (X = Cl, Br, J) leads to deeper understanding of the character of bonds in the crystal lattice and points the way to a better utilization of technical properties of the crystals. — Minimum velocity of propagation of an elastic wave falls in the case of Hg₂J₂ to a value v [100] [11 10] = 0,25 · 10⁵ cm/s, what is the lowest value known among all crystals. Maximum angular deviation of acoustic energy flux — nearly 50° — is exhibited by the quasi-longitudinal wave in Hg₂J₂ crystals. On substituting the Cl⁻ ions with Br⁻ and J⁻ ions, the anisotropy of elastic moduli C₃₃/C₁₁ increases by nearly 80%. Different mechanisms contribute to vectorial dependence of the elastic properties along different crystallographic directions.     

Microhardness of single crystals of the calomel family

Microhardness of Hg₂Cl₂, Hg₂Br₂ and Hg₂I₂ single crystals has been measured on (001) and (110) faces using the indenter after Vickers. It has been found that the microhardness of the first two homologues differs only slightly whereas the iodide is considerably softer: by about 20% on the (001) face and by about 30% on the (110) face. The average microhardness value, calculated from the values obtained on gradually rotating the indenter over 360° on the (001) face, is for Hg₂Cl₂ and Hg₂Br₂ practically equal to the microhardness of NaCl (20.3 and 19.4 compared to 19.6 · 10⁷ Pa). The average microhardness of the (110) face is for Hg₂Cl₂ and Hg₂Br₂ about 2 × lower and for Hg₂I₂ about 2.6 × lower than that of the (001) face. In the case of Hg₂Cl₂ the microhardness of the (001) face has been also calculated from crystallochemical parameters and the results have been found to be in good agreement with the value obtained experimentally for the orientation of the indenter's diagonal parallel to the [100] direction, where the data is the least influenced by the elasticity of the sample (16.6 compared to 18.6 · 10⁷ Pa).     

Equilibrium vapour pressures over NaCl-AgCl melts

The variation of vapour pressures over NaCl AgCl melts with increasing of AgCl mole fractions in the interval (0.00–0.33) has been studied at 1073 K by gas transport experiments. The vapour pressures of the individual species of silver chloride [(AgCl), (Ag₃Cl₃)] and of sodium chloride [(NaCl), (Na₂Cl₂)] have been calculated using thermodynamic data. The experimental and calculated results have been used for evaluation of the vapour pressures of the complex species Ag₂NaCl₃ and AgNa₂Cl₃ at the upper experimental conditions. The equilibrium constants of the following gas-phase reactions have been computed: 2 AgCl + NaCl ⇌ Ag₂NaCl₃, K_p1073K = 2.57 · 10⁶, AgCl + 2 NaCl ⇌ AgNa₂Cl₃, K_p1073K = 1.19 · 10⁷.     

The Precipitation of Barium Chromate with Slow Development of Supersaturation. Kinetics of the Crystal Growth

Slow barium chromate precipitation was studied in well-stirred solutions — final concentration 0.002 mole 1⁻¹ — at 20°C at mixing rates varying from 0.2 to 2 · 10⁶ mole 1⁻¹ sec⁻¹; the kinetics of the crystal growth process were studied by chemical analysis and by optical microscopy. The crystal growth started after induction periods; regular growth then took place on the nuclei formed during these periods. For the main growth, up to about seventy percent precipitation time, growth rates at any time depended on the (residual excess solute concentrations in solution)². Immediately after the induction periods, crystal lengths varied with growth time according to the relation, for the main growth, crystal lengths varied with growth time according to a more complex relation, where k_l is the rate constant for surface growth, R_c is the rate of development of metal salt concentration and K is a constant that depends on the number of precipitate crystals. After some growth time τ = τ^*, when l_τ = l_τ*, all fresh solute added to the solution was utilised immediately and was deposited onto the growing crystals; then, for the final thirty percent precipitation, crystal lengths varied with growth time according to the relation, .     

Structural study of molten Ag halides and molten AgCl–AgI mixture

The structures of molten Ag halides and pseudo-binary mixtures between AgCl and AgI have been investigated by neutron diffraction measurements. For AgI, a crystalline local configuration persists even in the molten state while, for AgCl and AgBr, the first neighbor coordination number decreases to 3.4 compared with 6 in the crystalline rock salt structure and the second neighbor distribution is modified according to the shortening of Ag–halogen distance. This difference between AgI and AgCl (AgBr) may be originated from the nature of unlike-pair bonding. The former has much covalent character. The eutectic mixture between AgCl and AgI, AgCl_0.43I_0.57, exhibits large temperature dependence in the total structure from the AgCl like feature at a lower temperature to the AgI like feature at a high temperature. As increasing temperature, Cl ions become more diffusive and relatively strong interaction between Ag and I rules physical property such as sound absorption.     

Structure of a five-coordinate mononuclear cobalt(II) complex: chlorobis([N,N-(1,1′-biphenyl-2,2′-dimethylene)]-2-aminomethyl) pyridine)cobalt(II) bromide

A penta-coordinate mononuclear cobalt(II) complex, [Co(BP)₂(Cl⁻)](Br⁻), 1 with a novel, biphenyl-appended N,N-bidentate ligand, BP ([N,N-(1,1′-biphenyl-2,2′-dimethylene)]-2-aminomethyl) pyridine) was synthesized and characterized by elemental analysis, UV-Vis, electro-spray ionization mass spectrum and single crystal XRD. The title complex crystallizes in the monoclinic space group C2/c with cell dimensions a = 11.389(2), b = 25.627(3), c = 12.276(3) Å, β = 100.419(18)° and Z = 2. The cobalt atom has a distorted trigonal bipyramidal (tbp) geometry and is surrounded by 4Ns of two BP, and a Cl⁻/Br⁻ at the 5th coordination site. This is the first report of a mononuclear tbp cobalt complex with biphenyl appended bidentate ligand containing amino-pyridyl moiety.     

Crystal structures of three methylmercury(II) complexes with thiazolidine-2-thione

The crystal structures of three CH₃Hg⁺ complexes with 1,3-thiazolidine-2-thione (HT) are reported. The cationic [(CH₃Hg)HT]NO₃ complex is monoclinic, space group P2₁/c,a=7.158(14),b=10.156(7),c=13.472(12) Å,=108.21(4)°,Z=4. The structure was refined toR=0.045. The [(CH₃Hg)HT]⁺ cation contains a CH₃Hg⁺ group bonded to the exocyclic S atom of the ligand retaining its N-H proton. This proton is lost and the CH₃Hg⁺ group remains bonded to sulfur in the neutral [(CH₃Hg)T] compound (hexagonal, P6₃,a=13.502(8),c=6.984(7) Å,Z=6,R=0.027). The [(CH₃Hg)₂T]NO₃ compound (monoclinic, C2/c,a=25.200(10),b=7.029(6),c=17.946(8),=128.99(3)°,Z=8,R=0.047) contains complex cations in which the CH3Hg⁺ groups are bonded to N and the exocyclic S atom. This series of compounds shows that the exocyclic S atom is always the first target for the CH₃Hg⁺ group, which is also found to bind to nitrogen in the 2:1 compound. No coordination is observed with the endocyclic S site, which does not even participate in intermolecular H-bonding or HgS contacts in the solids.     

Influence of a Halide Ion on Ribbons of Water Pentamer

Abstract  Reactions of CuF₂, CuCl₂ · 2H₂O and CuBr₂ with 2,2′-dipyridylamine (HDPA) in water at room temperature using Cu:HDPA = 2:1 mol yield [Cu(HDPA)(H₂O)₂F]F · 3H₂O (1), Cu(HDPA)Cl₂ (2) and Cu(HDPA)Br₂ (3) respectively. The structures of 2 and 3 are isostructural in spacegroup C2 with cell dimensions; for 2, a = 14.702(8), b = 7.726(2), c = 4.829(6) ?, β = 96.68(8)° and for 3, a = 14.2934(8), b = 7.9057(6), c = 5.1982(5) ?, β = 94.049(7)°. In the X-ray crystal structure, the complex 1 is found to contain tapes of water pentamers. Our DFT calculations at the B3LYP/LanL2DZ level show that the reaction Cu(HDPA)X₂ + 2H₂O = [Cu(HDPA)(H₂O)₂X]X is most exothermic in the gas phase when X⁻ = F⁻, i.e., the tendency of water uptake is maximum for Cu(HDPA)F₂. It seems that the exothermicities of the aquations of Cu(HDPA)Cl₂ and Cu(HDPA)Br₂ are not sufficient to stabilise the type of ribbons of water observed in 1 and consequently water is eschewed when X⁻ = Cl⁻ or Br⁻. Graphical Abstract  Cu(2,2′-dipyridylamine)X₂ takes up water to produce ribbons of water pentamer, as shown in the accompanied picture (red: O atom of a solvent water molecule), only when X⁻ is F⁻ but not when it Cl⁻ or Br⁻. The results are rationalised by means of DFT calculations at the B3LYP/LanL2DZ level. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The precipitation of calcium carbonate powders from aqueous solution with slow development of supersaturation. Induction periods,crystal numbers and final sizes

The precipitation of calcium carbonate was studied by slow addition of anion solution to excess cation solution and by slow mixing of equivalent cation land anion solutions at 20 °C: the final solute concentrations (C_fin were varied from 0.01 to 0.75 mole 1⁻¹ while the rates (R) of addition of ions were varied from 0.06 to 6 · 10⁻³ ion 1⁻¹ sec⁻¹. At first, mainly heterogeneous nuclei formed continuously during induction periods; then, as the metal salt concentration in solution increased, some more heterogeneous nuclei formed but homogeneous nucleation soon predominated. The second nucleation process probably attained its maximum rate when the metal salt concentratio in solution reached its maximum value (C_max) and then probably terminated quite rapidly. Some further nuclei also formed during the growth process when crystal growth was prolonged. The final nucleus numbers (N) (and thence the crystal numbers) for slow precipitations from dilute solutions were then rather higher than the optimum number N∞ (het) of heterogeneous nuclei in the solution; nucleus numbers then increased with increasing maxing rate according to the relations . These numbers were similar to those noted for rapid precipitation – onto homogeneous nuclei – from calcium carbonate solutions of concentrations somewhat lower than the C_max values. The final average crystal lengths of any precipitate then generally varied with mixing rate according to the relations, . where l₁ values increased with (C_fln)^0.33.     

Copper(II) and lead(II) complexes of 4,4′-bipyridine-<Emphasis Type="Italic">N,N</Emphasis>′-dioxide

Cu(II) and Pb(II) complexes of 4,4′-bipyridine-N,N′-dioxide have been prepared using a solvent-layering system. [Cu₂Cl₄(bpdo)₃(H₂O)₂] . 2(CH₃)₂SO (1) crystallises in P-1, a=8.731(2), b=8.943(2), c=14.408(3) ?, α=102.85(3), β=97.49(3), γ=109.77(3)°. The Cu(II) complex is a z-shaped discrete molecule with a DMSO molecule hydrogen bonded to the host through coordinated water molecule. Crystallisation of PbCl₂, PbBr₂ and PbI₂ with bpdo afforded isostructural 2D coordination polymers. [PbCl₂(bpdo)]_n is monoclinic, C2/c with a=16.3274(7), b=4.0708(1), c=18.6146(8) ?, β=93.73(1)°; [PbBr₂(bpdo)]_n is monoclinic, C2/c with a=16.403(3), b=4.2412(8), c=18.846(4) ?, β=92.59(3)° and [PbI₂(bpdo)]_n is monoclinic, C2/c with a=16.438(3), b=4.538(1), c=18.973(4) ?, β=91.04(3)°. The adjacent metal centres of these polymers are bridged by coordinated Cl⁻, Br⁻ or I⁻ anions as well as by bpdo ligands. These polymers possess no conventional hydrogen bonds.     

Calcium-free Solid Solutions in the System Ba<Subscript>7</Subscript>F<Subscript>12</Subscript>Cl<Subscript>2−x</Subscript>Br<Subscript>x</Subscript> (x < 1.5), a Single-component White Phosphor Host

We have recently prepared solid solutions of Ba_～6.3Ca_～0.7F₁₂Cl_2?xBr_x with x ranging from 0 to 2. In this work, the synthesis and single crystal X-ray structure of calcium-free crystals of Ba_～6.9Na_～0.2F₁₂Br_0.6Cl_1.4 (space group P6₃/m, a = 10.6024(10), c = 4.2034(4) Å), Ba_～6.9Na_～0.2F₁₂Br_1.4 Cl_0.6 (space group P6₃/m, a = 10.6155(9), c = 4.2355(4) Å) and Ba_～6.9Na_～0.2Br_1.32Cl_0.68F₁₂ (space group P6₃/m, a = 10.6218(9), c = 4.2284(4) Å) are reported.These crystals systematically present additional electron density at the 0 0 0.25 position which is associated with the presence of small, but significant amounts of Na⁺ ions in the crystal.     

Crystal structures and magnetic properties of bipyridine copper(II) complexes

The synthesis, structure and magnetic properties of [Cu(diMe-bipy)Br₂] are reported (diMe-bipy=4,4-dimethyl 2,2-bipyridine). The complex has a polymeric structure composed of [Cu(diMebipy)Br₂] subunits linked via bridging bromine atoms. Each copper atom is hexacoordinated in a distorted octahedral coordination environment. Crystallographic data: monoclinic, space groupC2/c,Z=4, unit cell of dimensionsa=18.312(7),b=9.818(2),c=7.486(2)Å,=107.750(0)° at 293 K. The best fit of the magnetic susceptibility data by the uniform Heisenberg chain model forS=1/2 ions yields values for the exchange coupling constant of –0.46 cm^–1. The magnetic susceptibility of the dimeric [Cu(diMe-bipy)Cl₂]₂·0.5H₂O exhibits a maximum near 12 K that is indicative of an antiferromagnetic interaction between the two metal centers. The best fit of the experimental data by the Bleaney-Bowers equation was obtained withg=1.95 andJ=–6.99 cm^–1.     

Crystal and Molecular Structure of Piperidinium-acet-m-Cl-anilide-chloride

Piperidinium-acet-m-Cl-anilide-chloride crystallizes in the orthorhombic space group Pca2₁ with 4 formula units C₁₃H₁₈ON₂Cl₂ in the unit cell. The lattice parameters are a = 10.348 Å, b = 12.280 Å and c = 11.335 Å. The crystal structure was determined by the heavy atom method and refined by least-squares procedures to the conventional R = 0.045. Bond lengths, bond angles and the conformation of the drug molecule were determined. Cl⁻ ions are linked to the molecules by hydrogen bonds forming chains together with iones and molecules related by the a-glide plane.     

X-ray diffraction structure of the 1,1′-bis(diphenylphosphino)ferrocene (dppf)-bridged complex [(dppf)AgCl]2: An unexpected product from the reaction betweencis-(bpy)2RuCl2 and dppf in the presence of AgBF4

The reaction betweencis-Ru(bpy)₂Cl₂ (where bpy=bipyridine) and the diphosphine ligand 1,1-bis(diphenylphosphino)ferrocene (dppf) in the presence of AgBF₄ has led to the isolation of the title compound [Ag(dppf)Cl]₂. [Ag(dppf)Cl]₂ has been structurally characterized by X-ray diffraction analysis, which confirms the bridging mode adopted by the ancillary dppf ligand and the centrosymmetric nature of this molecule. Dimeric [Ag(dppf)Cl]₂ crystallizes in the triclinic space group ,a=11.426(1) Å,b=11.509(1) Å,c=12.786(1) Å, =68.96(2)°, =70.66(2)°, =71.24(2)°,V=1441(1) ų,Z=1,d _calc=1.608 g·cm^–3;R=0.0445,R _w=0.0566 for 4486 observed reflections withl>3(l)     

Synthesis and crystal structure of di(2-aminopyrimidinium) trichlorodimethyl(2-aminopyrimidine)stannate(IV) chloride (H-2APY)2[SnMe2Cl3(2APY)]Cl

The synthesis and molecular structure of di(2-aminopyrimidinium) trichlorodimethyl(2-aminopyrimidine)stannate(IV) chloride (H-2APY)₂[SnMe₂Cl₃(2APY)]Cl is reported. The compound crystallized in the orthorhombic space group Pnma with a = 20.524(1) Å, b = 10.822(1) Å, c = 10.472(1) Å and V = 2325.9(3) ų, Z = 4. The structure consists of three fragments: the hexacoordinated organotin anionic complex [SnMe₂Cl₃(2APY)]⁻, which exhibits distorted octahedral geometry; two protonated 2-aminopyrimidinium cations (H-2APY)⁺, and one chloride anion.

     

The precipitation of barium sulphate and chromate powders from aqueous solution with slow development of supersaturation. Crystal numbers and final crystal sizes

The precipitations of barium sulphate and chromate were studied by slow addition of anion to metal cation solution at 20°C, to give final equivalent metal salt solutions; the final solute concentrations (C_fin) were varied from 0.002 to 0.30 mol l⁻¹ while the rates (R) of addition of anion were varied from 10⁻⁴ to 10⁻² ion l⁻¹. At first, mainly heterogeneous nuclei formed continuously during induction periods; then, as the metal salt concentration in solution increased, homogeneous nucleation soon predominated. This second nucleation process probably attained its maximum rate when the metal salt concentration in solution reached its maximum value (C_max) and then probably terminated quite rapidly. Some further nuclei also formed during the growth process when crystal growth was prolonged. The final nucleus numbers (N), and thence the crystal numbers for slow precipitations from very dilute solutions were then rather higher than the number N ∞ (het) of heterogeneous nuclei in solution: nucleus numbers then increased with increasing mixing rate according to the relation, (where β = 0.7–0.9) (where β = 0.7–0.9). The final average crystal lengths of any precipitate were then 2 to 40 times the sizes noted for rapid precipitation from equivalent solutions of the same concentration: generally, final lengths varied with mixing rate according to the relation, .     

Air-stable liquid clathrates. 1. Crystal structure of [NBu4][Br3] and reactivity of the [NBu4][Br3]·5 C6H6 liquid clathrate

[NBu₄][Br₃] interacts with C₆H₆ to form an air-stable liquid clathrate. The tribromide anion reacts with phenol to give para-bromophenol in>95% yield. The HBr which is generated in the reaction combines with the Br^– anion to form [Br-H-Br]^–. The latter forms the basis for a new liquid clathrate, [NBu₄][Br-H-Br]·n C₆H₆. The parent salt, [NBu₄][Br₃], crystallizes in the monoclinic space group C2/c witha=12.983(5),b=10.380(7),c=16.222(6) Å,=93.93(3)°, andD _c =1.47 g cm^–3 forZ=4. The final R value is 0.068 based on 787 observed reflections.     

Ultraviolet Absorption of Hg2Cl2-and Hg2Br2 Single Crystals

The optical unpolarized absorption spectra of Hg₂Cl₂ and Hg₂Br₂ single crystals were measured in the spectral range 230–400 nm. A sharp exciton peak and other absorption bands of both halides were observed near the fundamental absorption edge. The absorption peaks due to the splitting of the halogen doublet were also observed. Positions of the exciton peaks are characteristic for the Frenkel (localized) type of excitons. Possible interpretations of the other observed bands are discussed.     

Molecular and crystal structure of Cp2Mo(mto), mto=monothiooxalate

Compoundl, Cp₂Mo(mto) is obtained by the reaction of Cp₂MoCl₂ with methanol solutions of potassium dithiooxalate in air. Red platelike crystals of Cp₂Mo(mto) were grown by the slow diffusion of pentane into a CH₂Cl₂ solution ofl and have been studied by X-ray crystallography: space group, P2₁/n,a=7.578(1),b=10.551(2),c=14.090(3) Å, =94.38(2)°,V=1123.1(4) ų,Z=4. The mto ligand chelates to the Mo atom through one oxygen atom and the sulfur atom. The two Cp rings form dihedral angles of 24° with the least-squares plane of the mto ligand. The Mo–O and Mo–S bond distances are 2.193(5) and 2.449(2) Å, respectively.