Iron environment in calcium-soda-phosphate glasses and vitroceramics

The structure of calcium-soda-phosphate glasses and vitroceramics with relatively high iron content was investigated by X-ray diffraction, electron paramagnetic resonance (EPR) and Mössbauer spectroscopy. The X-ray diffraction analysis proves the vitreous state of the as prepared samples and the development of crystalline phases in the annealed samples. The ferric ions disposed in sites that give rise to the absorption line with g_ef ≈ 4.3 in the EPR spectra of vitreous samples are not more evidenced in the spectra of the annealed samples, from which only of a symmetric and narrowed line with g_ef ≈ 2 is recorded. The room temperature ⁵⁷Fe Mössbauer spectra both of glass and vitroceramic samples consist of two quadrupole doublets characteristic for octahedral sites of Fe²⁺ and Fe³⁺ ions. The isomer shift for glass samples decreases and for vitroceramic samples increases with the iron oxide content.     

CO replacement in Ru3(CO)12 by 2,3-bis(diphenylphosphino)maleic anhydride (bma). X-ray structures of Ru3(CO)10(bma)·H2O and

Thermolysis of Ru₃(CO)₁₂ with 2,3-bis(diphenylphosphino)maleic anhydride (bma) in toluene solution gives the new compounds Ru₃(CO)₁₀(bma) (2), Ru₂(CO)₆(bma) (3), and (4). All compounds have been isolated and characterized in solution by IR and³¹P NMR spectroscopy. The solid-state structures of2, as the monohydrate, and4 were established by X-ray crystallography. Ru₃(CO)₁₀(bma)·H₂O crystallizes in the monoclinic space groupC2/c,a=12.741(2) Å,b=19.548(2) Å,c=32.973(4) Å, β=96.847(9)°,V=8154(2) ų,Z=8,d _calc=1.740 g cm^?3;R=0.046,R _w =0.051 for 2541 observed reflections withl>3σ(l). The bma ligand in2 is bound to the triruthenium frame in a bridging fashion, with equatorially disposed PPh₂ groups. The X-ray structure of2 reveals an extreme twisting of the maleic anhydride ring away from the plane defined by the plane of the three ruthenium atoms, along with a significant lengthening of the maleic anhydride C=C π bond. crystallizes in the monoclinic space groupP2₁/c,a=9.3113(5) Å,b=18.164(1) Å,c=20.097(1) Å, β-102.021(4)°,V=3324.5(3) ų,Z=4,d _calc=1.671 g cm^?3;R=0.024,R _w =0.030 for 3499 observed reflections withl>3σ(l). The presence of the μ₂ moiety and P?C (maleic anhydride) bond cleavage attendant in the formation of4 are confirmed by X-ray analysis. The relationship of the compounds3 and4 to the dimeric compounds Ru₂(CO)₆(bpcd) and [where bpcd=4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione] is discussed. Independent studies dealing with Ru₃(CO)₁₀(bma) (bridging isomer) have shown that cluster2 is stable in toluene solution at elevated temperature and does not afford compounds3 and4, suggesting the intermediacy of the putative chelating isomer of Ru₃(CO)₁₀(bma) (1) as the source of3 and4.     

Molecular structure of AlH3[N(CH2CH2)3CH]2

Reaction of AlH₃[N(CH₂CH₂)₃CH] with hexamethyltrisiloxane, (OSiMe₂)₃, gives rise to the bis-quinuclidine complex AlH₃[N(CH₂CH₂)₃CH]₂, which has been characterized by ¹H and ¹³C NMR spectroscopy and X-ray crystallography. The molecular structure of AlH₃[N(CH₂CH₂)₃CH]₂ consists of a trigonal bipyramidal aluminum with axial coordination of the quinuclidine ligands. Crystal data: orthorhombic, space group Pbcn, a = 10.6895(9), b = 12.266(1), c = 12.3794(9) Å, V = 1623.2(2) ų, and Z = 4.     

Crystal structures of three substituted pentacyclo[5.4.0.02,6.03,10.05,9]undecanes

The crystal structures of three compounds formed via ultimate nucleophilic attack of unsaturated hydrocarbon fragments are reported. Geometries of the bis(vinyl)-, mono(vinyl), and bis(ethynyl)-substituted PCU species are unexceptional. The crystal structures are dictated by the availability of intermolecular hydrogen bonding.     

Molecular structures of M(tfac)3 (M=Al, Co) and Cu(H2O)(fod)2: Examples of unusual supramolecular architecture

The molecular structures of Al(tfac)₃ (1), Co(tfac)₃ (2) (H-tfac = 1,1,1-trifluoroacetylacetone) and Cu(H₂O)(fod)₂ (3) (H-fod = 1,1,1,2,2,3,3-hepta-fluoro-7,7-dimethyloctane-4,6-dione) have been determined. The metal coordination spheres in compounds 1 and 2 are essentially the same as the respective M(acac)₃ derivatives. Despite the isomorphous nature of the structures of compounds 1 and 2, the identity of the nearest intermolecular van der Waals contacts are altered by minor changes in the metal coordination sphere. The geometry about copper in compound 3 is close to that of an ideal square bipyramid with the -diketonate ligands occupying the basal plane. The water ligand in each molecule of compound 3 is hydrogen bonded to an oxygen of a -diketonate ligand on an adjacent molecule resulting in the formation of dimers, which form rods along the y-axis due to weak C–F···Cu interactions. Crystal data: (1) orthorhombic, Pca2₁, a = 14.949(3), b = 19.806(4), c = 13.624(3) Å, V = 4033(1) ų, and Z = 8, and (2) orthorhombic, Pca2₁, a = 14.930(3), b = 19.620(4), c = 13.540(3) Å, V = 3966(1) ų, and Z = 8,; (3) monoclinic, P2₁/c, a = 12.447(3), b = 10.486(2) c = 21.980(4) Å, = 102.65(3)°, V = 2799(1) ų, and Z = 4.     

Synthesis,spectroscopic studies,and x-ray crystallographic analysis of the organotin carbohydrate: 1,2∶3,4-di-O-isopropylidene-6-O-triphenylstannylmethyl-α-D-galactopyranose

The title organotin carbohydrate, C₃₁H₃₆O₆Sn, has been synthesized and its molecular structure has been determined in solution and in the solid state. NMR, infrared, mass and X-ray crystallographic techniques were used. The chiral molecules crystallize in the monoclinic space group P2₁ withZ=2. The triphenyltin and carbohydrate moieties are linked by a trans methylene-oxygen-methylene arrangement. The pyranosyl ring adopts a twist-boat conformation and the isopropylidene rings adopt different (half-chair and envelope) forms. Solution and solid-state conformations are similar as only three ¹³C shift values are greater than 2ppm; the ¹¹⁹Sn value is 12 ppm.     

Nucleophilic additions of primary and secondary amines to pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione

The crystal structures of three compounds formedvia nucleophilic attack of a heterocyclic secondary amine on PCU-8,11-dione, with the concomitant intramolecular attack of one keto oxygen on the carbon of the other ketone, are presented. In all three compounds, the bridging oxygen contains substantial p-character, and the bonds to the attacking nitrogen are significantly shorter than would be expected.     

Structure of the product formed via Cu(I)-promoted oxidative dimerization ofexo-8-ethynylpentacyclo[5.4.0.02,6.03,10.05.9]undecan-endo-8-ol

The structure consists of two acetyl-substituted PCU cages linked by a diyne fragment. The conformation about the linker is midway between staggered and eclipsed, and the acetyl groups are somewhat distorted due to the proximity to the bulky cage units.     

Crystal and molecular structure ofS-methyl(pentafluorosulfanyl)thiocarbamate

The X-ray structure of S-methyl(pentafluorosulfanyl)thiocarbamate, SF₅NHC(O)SCH₃, has been determined from three-dimensional diffractometer data and refined by full-matrix least-squares techniques. The crystals are monoclinic:P2₁/m,a=5.008 (5),b=7.811 (2),c=9.348 (4) Å, =99.08 (7)°, andZ=2; finalR=0.046 for 517 observed reflections. The structure comprises hydrogen-bonded (NHO) chains with the component monomers in thecis, cis-conformation, i.e., the arrangement of the nonhydrogen and nonfluorine atoms is nearly planar, the SF₅ group and the O are in acis position with respect to the C-NH bond, and the O and the CH₃ group are in acis position with respect to the C(O)-S bond. Theoretical methods including MNDO and molecular modeling were used to study the relative stabilities of the four possible conformations of SF₅NHC(O)SCH₃.     

Synthesis,Characterisation and Reactivity of Copper(I) Amide Complexes and Studies on Their Role in the Modified Ullmann Amination Reaction

A series of copper(I) alkylamide complexes have been synthesised; copper(I) dicyclohexylamide ( 1 ), copper(I) 2,2,6,6‐tetramethylpiperidide ( 2 ), copper(I) pyrrolidide ( 3 ), copper(I) piperidide ( 4 ), and copper(I) benzylamide ( 5 ). Their solid‐state structures and structures in [D₆]benzene solution are characterised, with the aggregation state in solution determined by a combination of DOSY NMR spectroscopy and DFT calculations. Complexes 1 , 2 and 4 are shown to exist as tetramers in the solid state by X‐ray crystallography. In [D₆]benzene solution, complexes 1 , 2 and 5 were found by using ¹H DOSY NMR to exist in rapid equilibrium between aggregates with average aggregation numbers of 2.5, 2.4 and 3.3, respectively, at 0.05 M concentration. Conversely, distinct trimeric, tetrameric and pentameric forms of 3 and 4 were distinguishable by one‐dimensional ¹H and ¹H DOSY NMR spectroscopy. Complexes 3 – 5 are found to react stoichiometrically with iodobenzene, in the presence or absence of 1,10‐phenanthroline as an ancillary ligand, to give arylamine products indicative of their role as potential intermediates in the modified Ullmann reaction. The role of phenanthroline has also been explored both in the stoichiometric reaction and in the catalytic Ullmann protocol.