Determination of silver carbonate in silver oxide(Ag2O) by infrared spectroscopy

Silver carbonate in silver oxide (Ag(2)O) is determined quantitatively by infrared spectroscopy. The deviation of the results from a mean line is +/-0.2% of Ag(2)CO(3) for samples containing only normal silver carbonate, and +/-0.4% of Ag(2)CO(3) for samples containing both normal and basic silver carbonate.     

Synthesis, crystal structure, and properties of two modifications of MgB(12)C(2)

Single crystals of two modifications of the new magnesium boride carbide MgB(12)C(2) were synthesized from the elements in a metallic melt by using tantalum ampoules. Crystals were characterized by single-crystal X-ray diffraction and electron microprobe analysis (energy-dispersive (EDX) and wavelength-dispersive (WDX) X-ray spectroscopy). Orthorhombic MgB(12)C(2) is formed in a Cu/Mg melt at 1873 K. The crystal structure of o-MgB(12)C(2) (Imma, Z=4, a=5.6133(10), b=9.828(2), c=7.9329(15) A, 574 reflections, 42 variables, R(1)(F)=0.0208, wR(2)(I)=0.0540) consists of a hexagonal primitive array of B(12) icosahedra with Mg atoms and C(2) units in trigonal-prismatic voids. Each icosahedron has six exohedral B--B and six B--C bonds. Carbon is tetrahedrally coordinated by three boron atoms and one carbon atom with a remarkably long C--C distance of 1.727 A. Monoclinic MgB(12)C(2) is formed in an Al/Mg melt at 1573 K. The structure of m-MgB(12)C(2) (C2/c, Z=4, a=7.2736(11), b=8.7768(13), c=7.2817(11) A, beta=105.33(3) degrees , 1585 reflections, 71 variables, R(1)(F)=0.0228, wR(2)(I)=0.0610) may be described as a distorted cubic close arrangement of B(12) icosahedra. Tetrahedral voids are filled by C atoms and octahedral voids are occupied by Mg atoms. The icosahedra are interconnected by four exohedral B--B bonds to linear chains and by eight interstitial C atoms to form a three-dimensional covalent network. Both compounds fulfill the electron-counting rules of Wade and Longuet-Higgins.     

Structural differences between two crystal modifications of poly(γ-benzyl L-glutamate)

X-ray diffraction patterns were obtained for as-cast and oriented films of poly(γ-benzyl L -glutamate) and a comparison was made of the molecular packing of the α-helices in forms B and C. Form B snowed Bragg reflections on the layer lines as well as on the equator. The spacings were explained by a monoclinic unit cell comprising two chains, with a = 29.0₆ Å, b = 13 2₀ Å, c = 27.2₇ Å α = γ = 90°. and β = 96°. The chains contained in this unit cell and consequently alternating in the crystal have opposite chain directions. Form C showed continuous scattering on the layer lines and reflections on the equator. This form, therefore, is a nematiclike paracrystal in which the packing of α-helices is periodic in the direction lateral to the chain axis (a = 14.8–115.2 Å, b = 14.3–14.8 Å, c = 27 Å, and γ = 118°–120°), but the relative levels of the chains along the chain axes are displaced. The formation of form C may be attributed to random placement of two chains with mutually opposite chain directions.     

The crystal structure of bis(trimethyltin)carbonate

The crystal structure of bis(trimethyltin)carbonate, (Me₃Sn)₂CO₃ shows the presence of different tin-atom sites in a polymeric structure which arises as a result of a tridentate mode of coordination of the carbonate dianion.     

Structures of two high-temperature Dy2TiO5 modifications

Single crystals of two structural modifications of high-temperature dysprosium titanate Dy₂TiO were grown. Using X-ray diffraction, the crystal structure of the cubic modification (space group Fd3m, a = 10.28(1)Å, Z = 10.4) was refined and the structure of a new monoclinic modification (space group B2/m, a = 10.33(1)Å, b = 3.653(5)Å, c = 7.306(6)Å, β = 90.00(7)°, Z = 2.4), which crystallizes in minor amounts together with the cubic phase, was determined. The lowering of symmetry from cubic to monoclinic is due to different distributions of the Dy³⁺ and Ti⁴⁺ cations over the sites present in the cubic cell.     

Synthesis and Crystal Structure of a Decanuclear Silver（I）-thiolate Compound Ag10S[S2P（OEt）2]8

A new decanuclear silver(I) compound Ag₁₀(μ₈‐S)(dtp)₈ [dtp=S₂P(OEt)₂] was isolated from a reaction mixture containing W₂S₄(dtp)₂ and AgN0₃, and its solid‐state molecular structure was determinated by X‐ray crystallography. The crystallographic study revealed that the compound contains a distorted mono‐capped quasi‐prism [Ag_io] with an octat‐bridging S atom at the center of the prism. The compound (C₃₂H₈₀Ag₁₀O₁₆P₈S₁₇, M_r=2592.46) crystallizes in the monoclinic P2₁/n space group, with a = 1.5111(5) nm, b=2.3656(8) nm, c=2.284(1) nm, β= 96.88(3)°, V=8.107(5) nm³, Z=4 and D,=2.12 g · cm^?3. The solution using direct method and full‐matrix least‐squares refinement led to R=0.066, Rw=0.078 for 3928 reflections with I3σ(I).     

Crystallographic report: Chain‐like crystal structure of [Ni(en)2Ag(CN)2] [Ag(CN)2]

[catena‐Bis(1,2‐diaminoethane)nickel(II)‐µ‐dicyanoargentate]‐dicyanoargentate, [Ni(en)₂Ag₂(CN)₄], was synthesized and its chain‐like crystal structure was determined by X‐ray crystal analysis. Copyright © 2005 John Wiley & Sons, Ltd.     

The reaction of H2Os3(CO)10 with trifluoroacetonitrile and the x-ray crystal structure of HOs3(CO)9(μ3-η2-HNCCF3)

The reaction of H₂Os₃(CO)₁₀ with CF₃CN in hexane at 80°C leads to two isomeric products. The isomer constituting the major product contains a 1,1,1-tri-fluoroethylidenimido ligand which bridges one edge of the Os₃ triangle via the nitrogen, atom and may be formulated as (μ-H)Os₃(CO)₁₀(μ-NC(H)CF₃) (I). The minor product, formulated as (μ-H)Os₃(CO)₁₀(μ-η²-HNCCF₃) (II), contains a 1,1,1-trifluoroacetimidoyl ligand which is also edge-bridging, being N-bonded to one Os atom and C-bonded to the other. Thermolysis of I and II in solution results in loss of a CO group in each case to give (μ-H)Os₃(CO)_9^? (μ₃-η²-NC(H)CF₃) (III) and (μ-H)Os₃(CO)₉(μ₃-η²-HNCCF₃) (IV), respectively, which, it is proposed, are structurally related to I and II, but with the CN group coordinated also to the third Os atom in place of a CO group. In the case of IV this proposal has been confirmed by an X-ray crystallographic analysis. The compound crystallises in space group C2/c with a = 14.258(7), b = 13.486(10), c = 18.193(8) Å, β = 92.68(4)°, and Z = 8. The structure was solved by a combination of direct methods and Fourier difference techniques, and refined by full-matrix least squares to R = 0.054 for 2489 unique observed diffractometer data. Reaction of I with Et₃P gives a 1 : 2 adduct which is formulated as (μ-H)Os₃(CO)₁₀[μ-N?C(H)(CF₃)PEt₃] (V) on the basis of NMR evidence.     

Addition of C2(CO2Me)2 to trans-MeIr(CO)(PPh3)2. Formation and isomerization of MeIr(CO)(PPh3)2[C2(CO2Me)2], and crystal structure of the thermodynamic isomer

The reaction of C₂(CO₂Me)₂ with trans-MeIr(CO)(PPh₃)₂ leads to a kinetic isomer which has been characterized by ¹H and ³¹P NMR and infrared spectra and to a thermodynamic isomer which has been characterized by ¹H and ³¹P NMR, infrared, microanalysis and X-ray crystallography. The isomerization occurs readily in solution at room temperature; somewhat more slowly at −20°C. The thermodynamically stable isomer of MeIr(CO)(PPh₃)₂[C₂(CO₂Me)₂] crystallizes in the centrosymmetric monoclinic space group P2₁/c with a 14.847(2), b 16.648(2), c 15.656(3) Å, β 90.595(14)°, V 3869.7(11) ų and Z = 4. Single-crystal X-ray diffraction data were collected with a Syntex P2₁ automated diffractometer (Mo-K_α radiation, 2θ 5–40°) and the structure was solved and refined to R_F 8.6% for all 3631 independent data (R_F 4.0% for those 2318 data with |F_o| > 6σ(|F_o|)). The Ir^I center has a trigonal-bipyramidal environment with the methyl ligand and one PPh₃ ligand occupying axial sites (Ir-Me 2.193(14), Ir-P(1) 2.425(4) Å). The C₂(CO₂Me)₂ ligand is π-bonded to the iridium atom and lies with its triple bond parallel to the equatorial coordination plane; the equatorial ligands are completed by the second PPh₃ ligand (Ir-P(2) 2.402(3) Å) and a CO ligand (Ir-CO 1.812(15) Å).     

Hydrothermal single-crystal growth in the systems Ag/Hg/X/O (X = VV, AsV): crystal structures of (Ag3Hg)VO4, (Ag2Hg2)3(VO4)4, and (Ag2Hg2)2(HgO2)(AsO4)2 with the unusual tetrahedral cluster cations (Ag3Hg)3+ and (Ag2Hg2)4+ and crystal structure of AgHgVO4

Single crystals of (Ag3Hg)VO4 (I), (Ag2Hg2)3(VO4)4 (II), AgHgVO4 (III), and (Ag2Hg2)2(HgO2)(AsO4)2 (IV) were grown under hydrothermal conditions (250 degrees C, 5 d) from starting mixtures of elementary mercury, silver nitrate, ammonium vanadate, and disodium hydrogenarsenate, respectively. All crystal structures were determined from X-ray diffraction data, and their chemical compositions were confirmed by electron microprobe analysis. I crystallizes in the tillmannsite structure, whereas II-IV adopt new structure types: (I) I4, Z = 2, a = 7.7095(2) A, c = 4.6714(2) A, 730 structure factors, 24 parameters, R[F2 > 2sigma(F2)] = 0.0365; (II) I42d, Z = 4, a = 12.6295(13) A, c = 12.566(3) A, 1524 structure factors, 55 parameters, R[F2 > 2sigma(F2)] = 0.0508; (III) C2, Z = 4, a = 9.9407(18) A, b = 5.5730(8) A, c = 7.1210(19) A, beta = 94.561(10) degrees , 1129 structure factors, 48 parameters, R[F2 > 2sigma(F2)] = 0.0358; (IV) P31c, Z = 2, a = 6.0261(9) A, c = 21.577(4) A, 1362 structure factors, 52 parameters, R[F2 > 2sigma(F2)] = 0.0477. The most striking structural features of I, II, and IV are the formation of tetrahedral cluster cations (Ag3Hg)3+ and (Ag2Hg2)4+, respectively, built of statistically distributed Ag and Hg atoms with a metal-metal distance of about 2.72 A. The electronic structure of these clusters can formally be considered as two-electron-four-center bonding. The crystal structure of III differs from the protrusive structure types insofar as silver and mercury are located on distinct crystallographic sites without a notable metal-metal interaction >3.55 A. All crystal structures are completed by tetrahedral oxo anions XO4(3-) (X = VV, AsV) and for IV additionally by a mercurate group, HgO2(2-).     

CS2在Ag-S键中的插入反应的研究(PPh3)2 Ag(S2CSBu^t)

白色的[Bu^tSAg]nPPh3溶于CS2中, 析出桔黄色晶体. 经X射线单晶结构分析其结构为(PPh3)2Ag(S2CSBu^t). 发现了一个CS2在Ag-S键中的插入反应. 此反应为可逆反应, 晶体在120-130℃失去CS2. 晶体属三斜晶系, 空间群P1,a=10.571(1), b=13.638(3), c=14.391(3)A, α=88.75(2), β=72.84(1), γ=80.58(1)°, V=1954.9A^3, Dc=1.36g/cm^3, Dm=1.36g/cm^3, Z=2. 3572个衍射点参与修正, R=0.045, Rw=0.043, Ag原子以变形四面体与硫代黄原酸配体Bu^tS-CS2的两个S原子及两个PPh3的P原子配位. 插入反应形成的CS3基团基本上共面, 其C-S键长比CS2中的键长明显加长, 而比单键的C-S键长要短, 并在红外光谱上出现特征吸收峰.     

The crystal structure of silver(I) 2,4,5-trichlorophenolate

The crystal structure of silver(I) 2,4,5-trichlorophenolate has been determined by X-ray diffraction and refined to a residual R = 0.031 for 1072 observed reflections. Crystals are orthorhombic, space group Pccn with 8 molecules in a cell of dimensions, a 11.455(4), b 23.75(1), c 5.645(1) Å. Each silver in the polymeric structure is bonded to three independent phenolate oxygens (Ag  O range, 2.317-2543(3) Å; OAgO range, 86.5–106.5(2)°). In addition there is an unusual symmetrical and directed phenyl carbon-silver bond (AgC, 2.443(5) Å) that completes a trigonal pyramidal stereochemistry about silver.     

A tris(alkyne)triosmium cluster with an open structure: crystal structure of [OS3(CO)8(Me2C2)3]

Reaction of [Os₃(CO)₈(Me₂C₂)₂] with Me₂C₂ at 70°C in toluene produces a tris(alkyne) substituted triosmium cluster, which has been shown crystallographically to contain a bent arrangement of osmium atoms. Two of the alkyne units are linked via a carbon-carbon bond to produce an osmacyclopentadiene ring, while the third alkyne unit remains independently coordinated to the cluster via two π-bonds.