An AB initio molecular orbital study of the NF2 and N2F4 molecules,and ESR hyperfine coupling constants in NF2

In this publication, we present the results of gaussian type orbital calculations of ESR hyperfine coupling constants in NF₂. We also present electron density maps for the molecule, and the results of a calculation of ΔH⁰₂₉₈ for the reaction N₂F₄ → 2NF₂.     

Hypothetical AlF3 crystal structures

Applying a structure prediction computer programme (GRINSP=Geometrically Restrained INorganic Structure Prediction), the occurrence of 6-connected 3D networks was investigated, through AlF₆ octahedra exclusive corner sharing. The five known AlF₃ varieties were reproduced (α-, β-, η-, κ- and τ-AlF₃) and seven hypothetical models were predicted. Among these still to be synthesized AlF₃ phases, one can recognize two known structure types (TlCa₂Ta₅O₁₅, Ba₄CoTa₁₀O₃₀) and some easy to imagine intergrowths; however, a few others are completely unexpected, though simple. A comparison of the ab initio total energies of all the structures is provided, leading to the conclusion that the virtual models could well be viable.     

Improved manufacture of AlF3 FROM H2SiF6

Experience gathered in aluminum fluoride production during nearly ten years and concurrent development work have resulted in an improved process technology amenable to a reliable large scale production.The recovery of fluoride values - as aluminum fluoride or cryolite - provides phosphate plants with marketable products and simultaneously alleviates the disposal of a hazardous waste product. Within the next years new plants featuring optimized processing conditions will go on stream.Within the framework of favorable conditions provided by the phosphate plant (e.g. amount and quality of acid, reuse of side products), process parameters (e.g. reaction, filtration, crystallization), equipment design (e.g. filters, vessels, dryer, calciner) and optimization of process stages were found to be decisive in obtaining reliably a good product at high yields.     

Etude catorimetrique de la decomposition thermique des sels de tetraflouroammonium (NF4)2NiF6 et NF4SbF6

The study of the thermal decomposition of the tetrafluoroammonium salts (NF₄)₂NiF₆ and NF₄SbF₆ by differential scanning calorimetry also gave enthalpies of decomposition for (NF₄)₂NiF₆ and NF₄SbF₆ of 134.7 ± 13.0 kJ mol^?1 and 245.6 ± 28.9 kJ mol^?1 respectively. The corresponding standard enthalpies of formation are found to be ?1033 and ?1649 kJ mol^?1 respectively.     

Electrochemical synthesis and application of NF3

Electrolytic production of nitrogen trifluoride (NF₃) was reviewed. Electrolytic production of NF₃ using a nickel anode is more useful method from view points of the yield and purity of NF₃, especially, free from carbon tetrafluoride (CF₄), but has a few problems to be solved. At present, electrolysis of a molten NH₄F-KF-HF system using a carbon anode is developing, because no anode consumption and no storage of nickel sludge in the melt take place.Reaction of NF₃ with phosphorus sulfide, preparation of functionally gradient fluorocarbon films and carbonaceous thin films by plasma technique using NF₃, and reactive ion etching of Si, SiO₂, and SiC using NF₃ plasma were reported for the purpose of development on application of NF₃.     

Synthesis and thermochemical properties of NF2-containing energetic salts

Ammonium, 1,5-diamino-4-methyl-tetrazolium and 4-amino-1-methyl-triazolium salts of 5-difluoroaminodifluoromethyl-tetrazolate (TA-CF₂NF₂) were prepared by metathesis reactions of silver 5-difluoroaminodifluoromethyl-tetrazolate and the corresponding iodides. All are thermally stable to ∼150 °C. The ammonium salt has a density of 1.88 g cm⁻³. The combination of the CBS-4 method and isodesmic bond separation reactions was found to be an economical and reliable method to estimate heats of formation for polyfluorinated molecules. The standard heats of formation () of ammonium 5-difluoroaminodifluoromethyl-tetrazolate was calculated to be −53.13 kcal mol⁻¹ using the CBS-4 method. While its detonation pressures (P) and velocities (D) were estimated using Cheetah 4.0: P = 28.78 GPa; D = 8490 m s⁻¹; detonation properties for 1,5-diamino-4-methyl-tetrazolium salts of 5-difluoroaminomethyltetrazolate (TA-CH₂NF₂), 5-difluoroaminotetrazolate (TA-NF₂) and 5-difluoroaminodinitromethyl-tetrazolate (TA-C(NO₂)₂NF₂) are also compared based on predicted densities and computed heats of formation.     

Spectroscopic characterization of crystalline AlF3 phases

A comprehensive spectroscopic characterization of all known crystalline AlF₃ phases (α-, β-, η-, κ-, θ-AlF₃) is presented for the first time in this study. Beside their X-ray diffraction powder patterns, which were already published in the literature, ²⁷Al and ¹⁹F MAS NMR, FT IR and XPS spectroscopic techniques were applied for all phases in a consistent manner. For all phases prepared the utilization of ²⁷Al satellite transition (SATRAS) NMR allowed to determine the quadrupolar parameters of the aluminium sites including their distributions.In addition, η-AlF₃ was isolated with high phase purity and characterized following a new preparation path different from those known so far in the literature.     

Ionization of NF3 by electron impact

The ionization and dissociative ionization of NF₃ by electron impact has been measured by Fourier transform mass spectrometry (FTMS). The total ionization cross-section rises to a maximum value of 2.4±0.4×10⁻¹⁶ cm² at 140 eV. Estimates of the total single ionization cross-section using ab initio energies with the binary encounter Bethe (BEB) [Y.K. Kim, M.E. Rudd, Phys. Rev. A 50 (1994) 3594] or Deutsch–Märk [Int. J. Mass Spec. 197 (2000) 37] models are roughly twice the measured values. The partial cross-sections creating NF_x⁺ (x=0, 1, 2, 3), F⁺, and NF_x²⁺ (x=1, 2, 3) are reported. Differences between the FTMS results and quadrupole data and fast atom beam results of Tarnovsky et al. [Int. J. Mass Spectrom. Ion Processes 133 (1994) 175] are discussed.     

Syntheses, structures, and properties of Ag4(Mo2O5)(SeO4)2(SeO3) and Ag2(MoO3)3SeO3

Ag₄(Mo₂O₅)(SeO₄)₂(SeO₃) has been synthesized by reacting AgNO₃, MoO₃, and selenic acid under mild hydrothermal conditions. The structure of this compound consists of cis-MoO₂²⁺ molybdenyl units that are bridged to neighboring molybdenyl moieties by selenate anions and by a bridging oxo anion. These dimeric units are joined by selenite anions to yield zigzag one-dimensional chains that extended down the c-axis. Individual chains are polar with the C₂ distortion of the Mo(VI) octahedra aligning on one side of each chain. However, the overall structure is centrosymmetric because neighboring chains have opposite alignment of the C₂ distortion. Upon heating Ag₄(Mo₂O₅)(SeO₄)₂(SeO₃) looses SeO₂ in two distinct steps to yield Ag₂MoO₄. Crystallographic data: (193 K; MoKα, λ=0.71073 Å): orthorhombic, space group Pbcm, a=5.6557(3), b=15.8904(7), c=15.7938(7) Å, V=1419.41(12), Z=4, R(F)=2.72% for 121 parameters with 1829 reflections with I>2σ(I). Ag₂(MoO₃)₃SeO₃ was synthesized by reacting AgNO₃ with MoO₃, SeO₂, and HF under hydrothermal conditions. The structure of Ag₂(MoO₃)₃SeO₃ consists of three crystallographically unique Mo(VI) centers that are in 2+2+2 coordination environments with two long, two intermediate, and two short bonds. These MoO₆ units are connected to form a molybdenyl ribbon that extends along the c-axis. These ribbons are further connected together through tridentate selenite anions to form two-dimensional layers in the [bc] plane. Crystallographic data: (193 K; MoKα, λ=0.71073 Å): monoclinic, space group P2₁/n, a=7.7034(5), b=11.1485(8), c=12.7500(9) Å, β=105.018(1) V=1002.7(2), Z=4, R(F)=3.45% for 164 parameters with 2454 reflections with I>2σ(I). Ag₂(MoO₃)₃SeO₃ decomposes to Ag₂Mo₃O₁₀ on heating above 550 °C.     

On the stability of NF4NO3 and a new synthesis of fluorine nitrate

The reaction of NF₄⁺SbF₆⁻ with alkali metal nitrates in either CH₃CN or SO₂ solution at low temperatures produces FONO₂ in quantitative yield. Attempts were unsuccessful to prepare FONO from NF₄SbF₆ and KNO₂ in an analogous manner.     

Zur kenntnis von AlF3 und InF3 [1]

The lattice constants of AlF₃ and InF₃ were redetermined (AlF₃: a = 4.9254(7) Å, c = 12.4472(52) Å; InF₃: a = 5.4103(7) Å, c = 14.3775(21) Å). Using single crystals, the structures of both fluorides were refined anisotropically. The Madelung Part of Lattice Energy, MAPLE, is calculated and compared with the MAPLE values of other fluorides. The structures are discussed with respect to and compared with hypothetical forms containing undisturbed closest packings of F_?.     

Substitution and addition reactions of NF4BF4 with aromatic compounds

Benzene, toluene, and nitrobenzene interact rapidly with NF₄BF₄ in anhydrous HF to give, almost exclusively, fluorine substituted aromatic derivatives. Up to four hydrogens can be replaced in a rapid reaction, before a much slower addition reaction takes over. The direction of the substitution in C₆H₆, C₆H₅CH₃ and C₆H₅NO₂ and the lack of side chain fluorination in C₆H₅CH₃ support an electrophillic substituion mechanism. These rapid substitution reactions are followed by much slower fluorine addition reactions to give the corresponding cyclo-hexadienes and -hexenes. These addition reactions were also studied separately using tetra-, penta- and hexa- fluorobenzene as the starting materials. In these addition reactions, almost no hydrogen substitution occured. The addition of the first pair of fluorines always gave 1,4-cyclohexadienes in which CF₂ group was adjacent to hydrogen on the ring. The addition of the second pair of fluorines resulted in the formation of cyclohexenes. These reactions occured in high yield and offer a controlled, high yield path to dienes. All products were characterized spectroscopically and by comparison to literature data.     

Ab initio studies of the NF2Li and NHLi2 dimers

In an attempt to elucidate the nature of the dimeric bond in NLiX₂ compounds, ab initio calculations with 3-21G and 6-31G* basis sets are performed on NF₂Li and NHLi₂. The former exhibits an asymmetric structure, with a binding energy about half that of the NH₂Li dimer, while the latter features C_2v symmetry and a binding energy approximately the same as that of (NH₂Li)₂. It is concluded that the dimerization occurs via a contribution of covalent bonding.     

Thermal behaviour of two new salts of malonic acid: Cu(C3H2O4)·4H2O and Cu(NH4)2(C3H2O4)2

Two new salts of malonic acid have been prepared: the copper(II) malonate tetrahydrate and the copper(II)-ammonium double malonate. Their study by thermal analysis (TG and DTA) leads to the following results:Cu(C₃H₂O₄)·4H₂O: the dehydration is rather complex and it is only under careful conditions that an intermediate hydrate Cu(C₃H₂O₄)·3H₂O could be traced. At about 170°C the dehydration is not ended (the salt holds yet about 0.15H₂O) and the anhydrous salt occurs only at about 240°C. It decomposes immediately leading to residues the composition of which depends upon the surrounding atmosphere; the part played by the gas given off is discussed.Cu(NH₄)₂(C₃H₂O₄)₂: this salt melts and decomposes simultaneously at about 190°C. During the decomposition the copper nitride Cu₃N forms as intermediate compound (as well as copper metal). Concerning the final residues of the decomposition the results and the conclusions are the same as the ones of the previous case.     

Crystallographic data on bis-tetrafluoroammonium hexafluoronickelate (IV), (NF4)2NiF6

X-ray diffraction studies on both powdered and single crystal samples of (NF₄)₂NiF₆ have shown that the compound crystallises in a tetragonal form derived from the K₂ PtCl₆ structure. The space group is I 4/m and the unit cell dimensions are : a = 6.828 (5) Å, c = 9.270 (9) Å, c/a = 1.358, and Z = 2.     

Syntheses, crystal structures and spectroscopic properties of KEu[AsS4], K3Dy[AsS4]2 and Rb4Nd0.67[AsS4]2

Three rare earth compounds, KEu[AsS₄] (1), K₃Dy[AsS₄]₂ (2), and Rb₄Nd_0.67[AsS₄]₂ (3) have been synthesized employing the molten flux method. The reactions of A₂S₃ (A = K, Rb), Ln (Ln = Eu, Dy, Nd), As₂S₃, S were accomplished at 600 °C for 96 h in evacuated fused silica ampoules. Crystal data for these compounds are: 1, monoclinic, space group P2₁/m (no. 11), a = 6.7276(7) Å, b = 6.7190(5) Å, c = 8.6947(9) Å, β = 107.287(12)°, Z = 2; 2, monoclinic, space group C2/c (no. 15), a = 10.3381(7) Å, b = 18.7439(12) Å, c = 8.8185(6) Å, β = 117.060(7)°, Z = 4; 3, orthorhombic, space group Ibam (no. 72), a = 18.7333(15) Å, b = 9.1461(5) Å, c = 10.2060(6) Å, Z = 4. 1 is a two-dimensional structure with ²_∞[Eu(AsS₄)]⁻ layers separated by potassium cations. Within each layer, distorted bicapped trigonal [EuS₈] prisms are linked through distorted [AsS₄]³⁻ tetrahedra. Each Eu²⁺ cation is coordinated by two [AsS₄]³⁻ units by edge-sharing and bonded to further two [AsS₄]³⁻ units by corner-sharing. Compound 2 contains a one-dimensional structure with ¹_∞[Dy(AsS₄)₂]³⁻ chains separated by potassium cations. Within each chain, distorted bicapped trigonal prisms of [DyS₈] are linked by slightly distorted [AsS₄]³⁻ tetrahedra. Each Dy³⁺ ion is surrounded by four [AsS₄]³⁻ moieties in an edge-sharing fashion. For compound 3 also a one-dimensional structure with ¹_∞[Nd₀.₆₇(AsS₄)₂]⁴⁻ chains is observed. But the Nd position is only partially occupied and overall every third Nd atom is missing along the chain. This cuts the infinite chains into short dimers containing two bridging [As₄]³⁻ units and four terminal [AsS₄]³⁻ groups. 1 is characterized with UV/vis diffuse reflectance spectroscopy, IR, and Raman spectra.     

Syntheses, crystal structures and Raman spectra of Ba(BF4)(PF6), Ba(BF4)(AsF6) and Ba2(BF4)2(AsF6)(H3F4); the first examples of metal salts containing simultaneously tetrahedral BF4 and octahedral AF6 anions

In the system BaF₂/BF₃/PF₅/anhydrous hydrogen fluoride (aHF) a compound Ba(BF₄)(PF₆) was isolated and characterized by Raman spectroscopy and X-ray diffraction on the single crystal. Ba(BF₄)(PF₆) crystallizes in a hexagonal space group with a=10.2251(4) Å, c=6.1535(4) Å, V=557.17(5) Å³ at 200 K, and Z=3. Both crystallographically independent Ba atoms possess coordination polyhedra in the shape of tri-capped trigonal prisms, which include F atoms from BF₄⁻ and PF₆⁻ anions. In the analogous system with AsF₅ instead of PF₅ the compound Ba(BF₄)(AsF₆) was isolated and characterized. It crystallizes in an orthorhombic Pnma space group with a=10.415(2) Å, b=6.325(3) Å, c=11.8297(17) Å, V=779.3(4) Å³ at 200 K, and Z=4. The coordination around Ba atom is in the shape of slightly distorted tri-capped trigonal prism which includes five F atoms from AsF₆⁻ and four F atoms from BF₄⁻ anions. When the system BaF₂/BF₃/AsF₅/aHF is made basic with an extra addition of BaF₂, the compound Ba₂(BF₄)₂(AsF₆)(H₃F₄) was obtained. It crystallizes in a hexagonal P6₃/mmc space group with a=6.8709(9) Å, c=17.327(8) Å, V=708.4(4) Å³ at 200 K, and Z=2. The barium environment in the shape of tetra-capped distorted trigonal prism involves 10 F atoms from four BF₄⁻, three AsF₆⁻ and three H₃F₄⁻ anions. All F atoms, except the central atom in H₃F₄ moiety, act as μ₂-bridges yielding a complex 3-D structural network.     

Syntheses and properties of Re(III) complexes derived from hydrotris(1-pyrazolyl)methanes: molecular structure of [ReCl2(HCpz3)(PPh3)][BF4]

The complexes [ReCl₂{N₂C(O)Ph}(Hpz)(PPh₃)₂] (1) (Hpz = pyrazole), [ReCl₂{N₂C(O)Ph}(Hpz)₂(PPh₃)] (2), [ReCl₂(HCpz₃)(PPh₃)][BF₄] (3) and [ReCl₂(3,5-Me₂Hpz)₃(PPh₃)]Cl (4) were obtained by treatment of the chelate [ReCl₂{η²-N,O-N₂C(O)Ph}(PPh₃)₂] (0) with hydrotris(1-pyrazolyl)methane HCpz₃ (1,3), pyrazole Hpz (1,2), hydrotris(3,5-dimethyl-1-pyrazolyl)methane HC(3,5-Me₂pz)₃ (4) or dimethylpyrazole 3,5-Me₂Hpz (4). Rupture of a C(sp³)-N bond in HCpz₃ or HC(3,5-Me₂pz)₃, promoted by the Re centre, has occurred in the formation of 1 or 4, respectively. All compounds have been characterized by elemental analyses, IR and NMR spectroscopy, FAB-MS spectrometry, cyclic voltammetry and, for 1 · CH₂Cl₂ and 3, also by single crystal X-ray analysis. The electrochemical E_L Lever parameter has been estimated, for the first time, for the HCpz₃ and the benzoyldiazenide NNC(O)Ph ligands.     

Investigation of phase equilibria in the systems K2SO4Sc2(SO4)3, Rb2SO4Sc2(SO4)3 and Cs2SO4Sc2(SO4)3

Phase diagrams of the systems K₂SO₄Sc₂(SO₄)₃, Rb₂SO ₄Sc₂(SO₄)₃ and Cs₂SO₄ Sc₂(SO₄)₃ have been investigated by X-ray diffraction phase analysis and differential thermal analysis techniques. A salient feature of all the systems is the formation of M₃Sc(SO₄)₃, which melt incongruently, and MSc(SO₄)₂, which on heating decompose in the solid state.