Crystal Structure of the Orthorhombic Modification of a Mononuclear Peroxotitanium(IV) Dipicolinate

The deep red diaquoperoxotitanium dipicolinate [TiO₂(C₇H₃O₄N) (H₂O)₂]2H₂O crystallises in a pleochroic triclinic and a nonpleochroic orthorhombic modification. The structure of the former has been reported earlier. The structure of the latter, described in this paper, has been determined from X-ray diffractometer data and refined to R = 0.034. In both forms the complex occurs as the free acid, but the modes of packing are completely different. Bond lengths and angles agree closely. As in the other peroxotitanium(IV) chelate structures so far determined, titanium has an approximately pentagonal bipyramidal coordination with the peroxo group and the chelate ligand occupying equatorial sites and the waters forming the apices. The relationship proposed earlier between the basicity of the ligands and the bond lengths and colours of the related compounds is substantiated. The final difference Fourier maps obtained with normal and modified refinement procedures clearly reveal bonding electron densities. They indicate a pentagonal bipyramidal sp³d³ hybridisation of titanium with bent Ti-O_peroxo bonds, again in agreement with the triclinic form and other peroxotitanium chelates.     

Die Kristallstruktur eines dinuklearen Peroxotitan(IV)-nitrilotriacetatkomplexes

Crystal Structure of a Dinuclear Peroxotitanium(IV)-Nitrilotriacetate Complex The structures of four peroxotitanium(IV) dipicolinates, with colours ranging from deep red to yellow orange, have been reported earlier, and a correlation between their colours and the variations of certain bond lengths has been proposed. This paper describes the pale yellow dinuclear peroxotitanium nitrilotriacetate complex Na₄[Ti₂O₅(C₆H₆O₆N)₂]11 H₂O. The monoclinic structure, space group B2/b, contains 25 independent non-hydrogen atoms and 17 hydrogen atoms. It has been determined from diffractometer data and refined to R = 3.2%. Titanium is again coordinated approximately pentagonal-bipyramidally. The μ-oxygen bridge occupies an axial position. The short (1.819 Å), nearly linear Ti–O–Ti bonds show double bond character. The titaniumperoxide bonds, however, are relatively long, thus confirming the rule proposed before: the more basic the axial ligands, the higher is the frequency of the absorption band, the longer are the Ti-peroxide bonds and the shorter are the axial distances. This is confirmed by electron density maps, which are to be discussed elsewhere in detail, showing bent Ti-peroxide bonds enclosing an angle of about 70° and a strong electron bridge on the μ-oxygen bond. Hydrogen bonding and the packing of the complexes is discussed.     

Fabrication and characterization of TiO2 photocatalytic thin film prepared from peroxo titanic acid sol

A novel sol–gel technique using the PTA (peroxo titanic acid) sol as precursor for the fabrication of TiO₂ photocatalytic thin film is introduced in this paper. The peroxo titanic acid sol was synthesized from titanyl sulfate (TiOSO₄), ammonia and peroxide solution (H₂O₂). The transparent and porous TiO₂ thin film was prepared via a sol–gel technique using PTA sol and polyethylene glycol (PEG) as precursor and template, respectively. The TiO₂ thin film samples were characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible spectrophotometry (UV–vis), X-ray photoelectron spectrum (XPS) and thermogravimetry and differential thermal analysis (TG-DTA) technique. The PTA sol displayed amorphous TiO₂ below 100 °C. The anatase phase formed at 200 °C to 700 °C. The crystallinity of anatase phase was improved with increasing temperature. The anatase crystals on the surface of TiO₂ film were strip-like, the size being about 100 nm in length and 40 nm in diameter. Addition of PEG to the PTA sol developed porous structures in the film and changed the size and shape of the particles. The surface of the film contained Ti, O and C elements and Na element that diffused into the film from the glass substrate. The photocatalytic performance of TiO₂ film was tested for the degradation of 10 mg/L methyl orange. The degradation of methyl orange solution reached 98.9% after irradiated for 180 min under UV light. The porous TiO₂ thin film exhibited high photocatalytic activity towards degrading methyl orange.     

Peroxofluorokomplexe der Übergangsmetalle. III,Darstellung, Kristallstruktur und Schwingungsspektren von K6Ta3(O2)3OF13 · H2O mit einem μ-Oxo-diperoxo-octafluoroditantalat(V)-Anion

Transition Metal Peroxofluoro Complexes. III. Preparation, Crystal Structure, and Vibrational Spectra of K₆Ta₃(O₂)₃OF₁₃ · H₂O Containing a m?-Oxo-diperoxo-octafluoroditantalate(V) Anion K₆Ta₃(O₂)₃OF₁₃ · H₂O has been prepared from solution and his crystal structure was determined by X-ray single crystal investigation: Space group Pnma, lattice constants a = 1 653.6 pm, b = 883.5 pm, c = 1 365.8 pm, Z = 4, R = 0.033. The compound yields [Ta(O₂)F₅]^2? groups as well as m?-oxo-bridged [Ta₂O(O₂)₂F₈]^4? anions with very diffrent O? O distances within the peroxo groups (139 pm vs. 164 and 175 pm) correlating well with the i.r. and Raman spectra. The different bonding in connection with an oxo-bridge is discussed.     

Zur Kenntnis der Hydrate des Typs MX2 · 1 H2O mit M = Sr,Ba und X = Cl,Br, I. Kristallstrukturen des Strontiumchlorid-Monohydrats,SrCl2 · 1 H2O,und des Strontiumbromid-Monohydrats,SrBr2 · 1 H2O

On Hydrates of the Type MX₂ · 1 H₂O with M = Sr, Ba and X = Cl, Br, I. Crystal Structures of Strontium Chloride Monohydrate, SrCl₂ · 1 H₂O, and Strontium Bromide Monohydrate, SrBr₂ · 1 H₂O The structures of SrCl₂ · 1 H₂O, orthorhombic, Pnma, a = 1088.1(1), b = 416.2(1), c = 886.4(1) pm, Z = 4, d_c = 2.92 Mg m^?3, R = 0.052 for 755 reflections, and of SrBr₂ · 1 H₂O, orthorhombic, Pnma, a = 1146.4(1), b = 429,5(1), c = 922.9(1) pm, Z = 4, d_c = 3.88 Mg m^?3, R = 0.056 for 762 reflections have been determined from a Patterson synthesis and refined by Fourier and Least Squares methods. The structure consists of [SrX₂ = H₂O]_n-layers normal to [100] and Sr? H₂O? Sr? H₂O-chains parallel [010]. The Sr? O distances are 265.1(3) pm, SrCl₂ · 1 H₂O, and 265.9(4) pm, SrBr₂ · 1 H₂O. The shortest Sr? Cl and Sr? Br distances (298.9(1) and 315.3(1) pm) are within the layers. The environment of oxygen and strontium is a distorted tricapped trigonal prism. The orientation of the water molecules has been determined from vibrational spectroscopic measurements. The hydrogen atoms H₁ and H₂ form bifurcated hydrogen bonds of different strength to neighbouring halide ions. The corresponding O···X distances are 331.9(4) and 320.2(4) pm, SrCl₂ · 1 H₂O, and 340.8(4) and 333.8(4) pm, SrBr₂ · 1 H₂O. The other O? X distances are between 310.3(5) and 323.7(5) pm, SrCl₂ · 1 H₂O, and 323.5(5) and 333.2(6) pm, SrBr₂ · 1 H₂O.     

Ein Titan(IV)-Komplex mit zwei koordinativ gebundenen Wassermolekülen: [(π-C5H5)2 Ti(H2O)2](NO3)2

A Titanium (IV) Complex with Two Coordinatively Bonded Water Molecules: [(π-C₅H₅)₂Ti(H₂O)₂](NO₃)₂ (π-C₅H₅)₂Ti(NO₃)₂ and H₂O react in acetone to form the diaquo complex [(π-C₅H₅)₂-Ti(H₂O)₂](NO₃)₂ ( A ). An X-ray analysis shows the titanium atom to be nearly tetrahedrally coordinated. Mean values of distances: Ti? O 2.01 Å, Ti? Z 2.03 Å (Z = center of ring); angles: O? Ti? O 92.7°, Z? Ti? Z 133.6°. Anions and cations are joined by hydrogen bonds to form strands that run in the direction of the crystallographic a axis. A crystallizes in the orthorhombic space group Pnma with Z = 4 and lattice parameters at ? 100°C a = 7.601(2), b = 13.458(4) and c = 13.139(4) Å.     

Zur Existenz der Verbindung K2TiOF4: Pyrohydrolytischer Abbau von K2TiF6 und thermochemisches Verhalten von K2Ti(O2)F4 · H2O

On the Existence of the Compound K₂TiOF₄: Pyrohydrolytic Degradation of K₂TiF₆ and Thermochemical Behaviour of K₂Ti(O₂)F₄ · H₂O In an attempt to prepare K₂TiOF₄ we used the following three ways; solid-state reaction of K₂TiF₆, TiO₂, and KF, pyrohydrolysis of K₂TiF₆ at 450 and 550°C, and thermal decomposition of K₂Ti(O₂)F₄ · H₂O. In each case the reaction products were mixtures of several compounds, always containing the kryolith-phase K_2+xTiO_xF_6?x and TiO₂. At 130°C K₂Ti(O₂)F₄ · H₂O forms K₂Ti(O₂)F₄ by loss of H₂O, and at 230°C the peroxogroup decomposes, yielding K₂TiOF₄ as main product. K₂TiOF₄ crystallizes tetragonally with the following lattice parameters: a = 769.7(1) and c = 1153.9(2)pm. The i.r. spectrum shows an absorption band at 810 cm^?1, pointing to infinite chains of ? Ti? O? Ti? O? .     

Synthesis and Crystal Structure of meso-Δ,Λ-μ-Peroxo-μ-hydroxobis[bis(ethylenediamine)rhodium(III)]trifluoromethane Sulfonate

The reaction of the meso-diol, Δ,Λ-[(en)₂Rh(OH)₂Rh(en)₂]⁴⁺, with aqueous H₂O₂ and 1 equiv. of NaOH at 90° forms the μ-peroxo-μ-hydroxo-bridged species Δ,Λ-[(en)₂Rh(O₂,OH)Rh(en)₂]³⁺ in a yield of ca. 50%. The compound was crystallized as perchlorate and trifluoromethanesulfonate salts. The structure of the latter salt was determined by single-crystal X-ray diffraction. The crystals are triclinic with space group P1 and lattice constants a = 11.895(5), b = 12.491(4), c = 13.053(5) Å, α = 103.98(3), β = 92.59(3), γ = 119.52(6)°. The distances of the metal centres to the bridging peroxo ligand are 1.999(8) and 1.983(6) Å. The O? O distance in the peroxo group is 1.521(14) Å, and the dihedral angle of the Rh? O? O? Rh unit deviates 65° from planarity. The peroxo complex reacts reversibly with acid, and spectrophotometric studies suggest that the reaction involves protonation of the peroxo bridge, with pK_a = 2.70(2) at 25° in 1M NaClO₄.     

Crystal structure of oxo(diperoxo)bipyridylmolybdenum(VI)

Yellow oxo(diperoxo)bipyridylmolybdenum(VI), C₁₀H₈MoN₂O₅, M_r = 332.1 crystallizes in the monoclinic space group P2₁/n, a = 6.261(3), b = 12.726(1) c = 13.752(3)A, β = 91.84(2)°, V = 1095.2(5)A³, Z = 4, D_c = 2.014(1) g/cm³, MoKα(λ = 0.7107A), μ = 11.8 cm^?1, T = 22(1)°C, R = 0.034, ωR = 0.040, number of reflections in least squares (F₀ > 2σ(F₀)) = 1125. The molybdenum coordination (distorted trigonal bipyramidal) is as in the corresponding chromium complex, C₁₀H₈CrN₂O₅ which has closely similar bond angles but is not isomorphous. The difference in MoN_apex and MoN_eq bond distances (2.312(5) and 2.199(5)A) is similar to that in the CrN_apex and CrN_eq distances (2.23(2) and 2.11(2)A). The MO distances for each peroxo ligand (ave. 1.910(2) and 1.950(2)A) are significantly different and slightly longer than those in the chromium complex as is the OO distance of 1.459(6)A. The latter is indicative of greater negative charge on the O₂ ligands, approaching that of O^2?₂ in the molybdenum complex.     

Effect of Solvation on Chemical Reactions,I. Addition of a Single Water Molecule to the H− + H2O → OH− + H2 Reaction

The gas phase chemical reaction, H^? + H₂O → H₂ + OH, and the effect of an additional water molecule on the reaction, H^?(H₂O) + H₂O → H₂ + OH(H₂O), have been investigated. The optimal structures and energies of the reactants, products, two stable intermediates, and the transition state connecting the two intermediates have been determined. The additional water molecule does not affect the potential surface congruently: it destabilizes the H(H₂O) minimum, but stabilizes the H₂ ?OH minimum and the transition state connecting the two intermediates. However, it stabilizes the products more than the H₂ ?OH^? minimum. Finally, in line with the reduction in the barrier height, the transition state for the H(H₂0) to H₂ ?OH^? isomerization moves further along the reaction path.     

Fluorphosphorylamide

The preparation of some new phosphorus-fluoroamides of the type RP(O)FNH₂ is described (R = CH₃O-, C₆H₅O-, NH₂-, C₂H₅O-, CH₃NH-, C₂H₅NH-, C₆H₅-, C₆H₁₁-, C₂H₅-, CH₃-, and C₆H₅S-). All of the R? P(O)FNH₂ compounds were prepared at ?80°C in diethylether from the corresponding difluorides RP(O)F₂ and ammonia: RP(O)F₂ + 2NH₃ → RP(O)FNH₂ + NH₄F. When P(O)FCl₂ is reacted with ammonia in a molar ratio of 1:4, the hitherto unknown diamide of the series P(O)F_3?n(NH₂)_n (n = 1,2,3) is formed. As starting compounds, CH₃OP(O)F₂ and CH₃NHP(O)F₂ were obtained for the first time. The shifts of characteristic valency frequencies and some nmr data are discussed in homologous series.     

Synthesis,spectroscopic characterization and crystal structure of disulfamethoxazole diaquo Ni(II) monohydrate

The novel disulfamethoxazole diaquo Ni(II) monohydrate, [Ni(sulfamethoxazole)₂(H₂O)₂]· H₂O, was synthesized, characterized by infrared and electronic spectroscopies and the crystal structure determined. The compound crystallized in the monoclinic centrosymmetric space group P2₁/c, with four asymmetric units per unit cell. The nickel atoms are in slightly distorted regular octahedra, coordinated by four nitrogen atoms, two from N-arylamine and two from N-sulfonamide with the apical positions occupied by two oxygen atoms from the water molecules.     

Peroxofluorokomplexe der Übergangsmetalle. VIII. Kristallstruktur von K2Ti(O2)F4 · 1/2 H2O. Strukturchemischer Vergleich und spektroskopische Daten der Verbindungen K2Ti(O2)F4 · xH2O (mit x = 1, 1/2, 0)

Transition Metal Peroxofluoro Complexes. VIII. Crystal Structure of K₂Ti(O₂)F₄. · 1/2H₂O. Structural Comparison and Spectroscopic Data of the Compounds K₂Ti(O)₂F₄ · xH₂O (x = 1, 1/2, 0) The yellow hemihydrat K₂Ti(O₂)F₄ · 1/2 H₂O crystallizes monoclinic (space group C2/c, a = 1680.5(6), b = 653.2(1), c = 1224.3(4) pm, β = 115.8(1)°, Z = 8, Rw = 0.038 for 1113 independent reflections). It contains isolated, dinuclear, di(μ-fluoro)-bridged [Ti₂(O₂)₂F₈]^4? anions, as known by orange coloured K₂Ti(O₂)F₄ · H₂O [1]. They are arranged in layers which are parallel to the (100) plane, whereas they are linked by hydrogen bonds forming infinite chains in K₂Ti(O₂)F₄ · 1/2 H₂O. Anhydrous K₂Ti(O₂)F₄ - even yellow - crystallizes monoclinic with a = 828.9(2), b = 1107.6(2), c = 1303.9(3) pm, β = 92.29(2)°. I.r. and Raman spectra of all compounds are listed and interpreted. On the basis of the UV spectra the different colours of some titaniumperoxofluoro compounds are discussed in relation to the titanium-peroxid bonding.     

Syntheses and structural determinations of the nine-coordinate rare earth metal: Na4[DyIII(dtpa)(H2O)]2·16H2O,Na[DyIII(edta)(H2O)3]·3.25H2O and Na3[DyIII(nta)2(H2O)]·5.5H2O

Three complexes, Na₄[Dy^III(dtpa)(H₂O)]₂?·?16H₂O, Na[Dy^III(edta)(H₂O)₃]?·?3.25H₂O and Na₃[Dy^III (nta)₂(H₂O)]?·?5.5H₂O, have been synthesized in aqueous solution and characterized by FT–IR, elemental analyses, TG–DTA and single-crystal X-ray diffraction. Na₄[Dy^III(dtpa)(H₂O)]₂?·?16H₂O crystallizes in the monoclinic system with P2₁/n space group, a?=?18.158(10)?Å, b?=?14.968(9)?Å, c?=?20.769(12)?Å, β?=?108.552(9)°, V?=?5351(5)?ų, Z?=?4, M?=?1517.87?g?mol^?1, D _c?=?1.879?g?cm^?3, μ?=?2.914?mm^?1, F(000)?=?3032, and its structure is refined to R ₁(F)?=?0.0500 for 9384 observed reflections [I?>?2σ(I)]. Na[Dy^III(edta)(H₂O)₃]?·?3.25H₂O crystallizes in the orthorhombic system with Fdd2 space group, a?=?19.338(7)?Å, b?=?35.378(13)?Å, c?=?12.137(5)?Å, β?=?90°, V?=?8303(5)?ų, Z?=?16, M?=?586.31?g?mol^?1, D _c?=?1.876?g?cm^?3, μ?=?3.690?mm^?1, F(000)?=?4632, and its structure is refined to R ₁(F)?=?0.0307 for 4027 observed reflections [I?>?2σ(I)]. Na₃[Dy^III(nta)₂(H₂O)]?·?5.5H₂O crystallizes in the orthorhombic system with Pccn space group, a?=?15.964(12)?Å, b?=?19.665(15)?Å, c?=?14.552(11)?Å, β?=?90°, V?=?4568(6)?ų, Z?=?8, M?=?724.81?g?mol^?1, D _c?=?2.102?g?cm^?3, μ?=?3.422?mm^?1, F(000)?=?2848, and its structure is refined to R ₁(F)?=?0.0449 for 4033 observed reflections [I?>?2?σ(I)]. The coordination polyhedra are tricapped trigonal prism for Na₄[Dy^III(dtpa)(H₂O)]₂?·?16H₂O and Na₃[Dy^III(nta)₂(H₂O)]?·?5.5H₂O, but monocapped square antiprism for Na[Dy^III(edta)(H₂O)₃]?·?3.25H₂O. The crystal structures of these three complexes are completely different from one another. The three-dimensional geometries of three polymers are 3-D layer-shaped structure for Na₄[Dy^III(dtpa)(H₂O)]₂?·?16H₂O, 1-D zigzag type structure for Na[Dy^III(edta)(H₂O)₃]?·?3.25H₂O and a 2-D parallelogram for Na₃[Dy^III(nta)₂(H₂O)]?·?5.5H₂O. According to thermal analyses, the collapsing temperatures are 356°C for Na₄[Dy^III(dtpa)(H₂O)]₂?·?16H₂O, 371°C for Na[Dy^III(edta)(H₂O)₃]?·?3.25H₂O and 387°C for Na₃[Dy^III(nta)₂(H₂O)]?·?5.5H₂O, which indicates that their crystal structures are very stable.     

Synthese und Kristallstruktur von Tetraphenylphosphonium-Aquabis(tetrasulfido)thionitrosyl-Osmat,PPh4[Os(NS)(S4)2(H2O)]

Synthesis and Crystal Structure of Tetraphenylphosphonium Aqua-bis(tetrasulfido)thionitrosyl Osmate, PPh₄[Os(NS)(S₄)₂(H₂O)] PPh₄[Os(NS)(S₄)₂(H₂O)] has been prepared as redbrown crystals by reacting PPh₄[OsNCl₄] with a solution of excess disodium tetrasulfide in dimethylformamide/H₂O and characterized by IR spectroscopy and by a crystal structure determination. Space group P2₁/n, Z = 4, structure solution with 4162 independent reflections, R = 0.059 for reflections with I > 2σ(I). Lattice dimensions at ?40°C: a = 1138.9(5), b = 1301.4(4), c = 2092.7(7) pm, β = 104.74(3)º. Os? N, Os? O, and Os? S distances are 175.2(12), 219.8(12), and 237.5(4)?239.1(4) pm, respectively. The Os?N?S moiety is approximately linear, with an OsNS angle of 171.2(7)º.     

Synthesis and Structure of Cobalt(III) α-Dimethylglyoximate [Co(DH)<Subscript>2</Subscript>(Py)<Subscript>2</Subscript>][H<Subscript>2</Subscript>F<Subscript>3</Subscript>]

The [Co(DH)₂(Py)₂][H₂F₃] complex (DH^? is the dimethylglyoxime residue) is synthesized and studied by X-ray diffraction analysis. Structural units of the crystal are complex cations [Co(DH)₂(Py)₂]⁺ and anions [H₂F₃]^?. Two residues of α-dimethylglyoxime linked by intramolecular hydrogen bonds O-H?O lie in the equatorial plane of the octahedral Co(III) complex, and two pyridine molecules occupy the apical positions. The H₂F ₃ ^? anion is formed due to the association of the F^? ion with two HF molecules through hydrogen bonds F-H?F. Weak intermolecular interactions C-H?F and C-H?O are observed in the crystal. The problem of the influence of these interactions on the packing of the complexes in crystal is discussed.     

Fluoride und Fluorosäuren. V. Kristallstruktur der 1:4-Phase im System Wasser-Fluorwasserstoff und eine neue Untersuchung einer der 1:2-Phasen

Fluorides and Fluoro Acids. V. Crystal Structure of the 1:4 Phase in the System Water-Hydrogen Fluoride and a New Investigation of One of the 1:2 Phases In the quasi binary system H₂O? HF the 1:2 phase of known crystal structure was recognized as the stable high-temperature phase. A more accurate redetermination of its structure (monoclinic, space group P2₁/c, Z = 4, a = 3.477, b = 6.024, c = 11.358 Å, β = 96.70° at ?100°C, R = 0.032 for 1356 observed MoKα data) confirmed the previous results of a layer structure formed by strong hydrogen bonds. H₃OF · HF appears besides H₃OHF₂ as a possible structural formula. — The crystal structure of the 1:4 phase of the system was also determined (triclinic, P1 , Z = 2, a = 5.574, b = 6.429, c = 6.874 Å, α = 115.79, β = 96.63, γ = 108.79° at ?113°C, R = 0.049 for 1942 observed MoKα data). By strong hydrogen bonds the atoms form rings, which are condensed to parallel ribbons. Possible structural formulae, based on the distribution of interatomic distances, are H₃OH₃F₄, H₃OH₂F₃ · HF and H₃OF · 3 HF. — Interatomic distances in the hydrogen bonds F? H…?F and O? H…?F of both structures and the known one of the 1:1 phase are discussed in comparison.     

Wasserstoffbrückenbindungen in o- und m-Phenylendiammonium-aquapentafluorometallaten(III) (MIII = Al,Cr, Fe)

Hydrogen Bonds in o- and m-Phenylenediammonium Aquapentafluoro Metallates(III) (M^III = Al, Cr, Fe) m- and o-Phenylenediammonium-[M^IIIF₅(H₂O)] compounds of Al, Cr and Fe were synthesized and characterized by X-ray single crystal structure analysis. All structures are described in the space group P2₁2₁2₁ (Z = 4). m-Ph(NH₃)₂²⁺ (Ph(NH₃)₂²⁺ = phenylenediammonium) compounds: Al : a = 6.489(2), b = 7.943(2), c = 18.204(2) Å, R/wR = 0.084/0.050 for 1 533 reflections; Cr : a = 6.571(2), b = 8.006(2), c = 18.456(3) Å, R/wR = 0.050/0.040 for 1 571 reflections; Fe : a = 6.608(2), b = 8.052(2), c = 18.424(4) Å, R/wR = 0.042/0.034 for 1 947 reflections. o-Ph(NH₃)₂²⁺ compounds: Al : a = 6.580(2), b = 7.891(2), c = 18.319(5) Å, R/wR = 0.050/0.045 for 2 370 reflections; Cr : a = 6.642(2), b = 7.954(2), c = 18.484(4) Å, R/wR = 0.065/0.043 for 2 041 reflections; Fe : a = 6.693(2), b = 7.995(4), c = 18.529(7) Å, R/wR = 0.035/0.033 for 2 651 reflections. Isolated distorted octahedral [M^IIIF₅(H₂O)]^2? anions are connected by double O? H ?F hydrogen bonds of alternating strength to form chains in the b direction. Those chains, packed in a pseudohexagonal way, are further linked by the ammonium functions of the phenylenediammonium cations to a 3 D hydrogen bond network.     

Adsorption of uranyl species onto the rutile (110) surface: a periodic DFT study

To model the structures of dissolved uranium contaminants adsorbed on mineral surfaces and further understand their interaction with geological surfaces in nature, we have performed periodic density funtional theory (DFT) calculations on the sorption of uranyl species onto the TiO₂ rutile (110) surface. Two kinds of surfaces, an ideal dry surface and a partially hydrated surface, were considered in this study. The uranyl dication was simulated as penta‐ or hexa‐coordinated in the equatorial plane. Two bonds are contributed by surface bridging oxygen atoms and the remaining equatorial coordination is satisfied by H₂O, OH^?, and CO₃^2? ligands; this is known to be the most stable sorption structure. Experimental structural parameters of the surface–[UO₂(H₂O)₃]²⁺ system were well reproduced by our calculations. With respect to adsorbates, [UO₂(L1)_x(L2)_y(L3)_z]ⁿ (L1=H₂O, L2=OH^?, L3=CO₃^2?, x≤3, y≤3, z≤2, x+y+2z≤4), on the ideal surface, the variation of ligands from H₂O to OH^? and CO₃^2? lengthens the U? O_surf and U? Ti distances. As a result, the uranyl–surface interaction decreases, as is evident from the calculated sorption energies. Our calculations support the experimental observation that the sorptive capacity of TiO₂ decreases in the presence of carbonate ions. The stronger equatorial hydroxide and carbonate ligands around uranyl also result in U?O distances that are longer than those of aquouranyl species by 0.1–0.3 Å. Compared with the ideal surface, the hydrated surface introduces greater hydrogen bonding. This results in longer U?O bond lengths, shorter uranyl–surface separations in most cases, and stronger sorption interactions.     

Cooperative effect of Fe and Ti species over Fe–Ti–Ox catalysts on the catalytic hydrolysis performance of hydrogen cyanide

FeO_x, TiO₂, and Fe–Ti–O_x catalysts were synthesized and used in the catalytic hydrolysis of hydrogen cyanide (HCN). Nearly 100% HCN conversion was achieved at 250 °C over the Fe–Ti–O_x catalyst. TiO₂ rutile was detected over TiO₂, but not over Fe–Ti–O_x, which suggested that the interaction between Fe and Ti species could inhibit the TiO₂ phase transition. Furthermore, the interaction between Fe and Ti species over Fe–Ti–O_x could promote the selectivity of NH₃ and CO. The mechanism of hydrolysis of HCN over FeO_x, TiO₂, and Fe–Ti–O_x can be given as follows: HCN + H₂O → methanamide → ammonium formate → formic acid → H₂O + CO.