The structures of fluorides X. Neutron powder diffraction profile studies of UF6 at 193°K and 293°K

Neutron diffraction studies on polycrystalline UF₆ have been carried out at 193°K and 293°K. At both temperatures, UF₆ is orthorhombic with the space group Pnma (D¹⁶_2h) and Z = 4. Measured lattice parameters are a = 9.924 (10) Å, b = 8.954 (9) Å, c = 5.198 (5)Å at 293°K and a = 9.843 (11), b = 8.920 (10), c = 5.173 (6) Å at 193°K. The neutron diffraction patterns were analyzed by the least-squares profile-fitting technique. The final values of $\text{R =}\text{∑}\text{i}\text{(|I}{}_{\mathrm{<mtext>o</mtext><mtext>i</mtext>}}\text{? I}{}_{\mathrm{<mtext>o</mtext><mtext>i</mtext>}}\text{|)/∑ I}{}_{\mathrm{<mtext>o</mtext><mtext>i</mtext>}}$ over the pattern points, where I_oi is a background corrected measured intensity, were 0.081 at 193°K and 0.133 at 293°K.On cooling, the hexagonal close-packing tends to become more regular, and the FF distances external to a UF₆ octahedron contract. The octahedra are nearly regular with a mean UF distance of 1.98 Å, a mean FF edge of 2.80 Å, and a FUF angle of 90.0° at 193°K.     

Dilute solution properties of poly(N-vinyl-3,6-dibromo carbazole)—III. Phase equilibrium studies

The phase relationships of poly(N-vinyl-3,6-dibromo carbazole) (PVK-3, 6-Br₂) were examined for four solvents, viz, o-chlorophenol, p-chloro-m-cresol, o-dichlorobenzene and bromobenzene. Upper critical solution temperatures (UCST) have been determined for solutions of PVK-3,6-Br, fractions in o-chlorophenol and p-chloro-m-cresol over the molecular weight range $\text{M}{}_{\mathrm{<mtext>w</mtext>}}\text{× 10}{}^{\mathrm{?4}}\text{= 125.0}\text{to}\text{4.8}$. The Flory temperature, θ, obtained from UCST for the PVK-3,6-Br₂/o-chlorophenol and PVK-3,6-Br₂/p-chloro-m-cresol systems are 66.0 and 112.9°C, respectively. The θ-temperatures were checked against molecular weight and viscosity data to determine the Mark-Houwink equations for these two theta solvents, with satisfactory agreement. The relations are

$\text{[ν] = 27.5}{}_4\text{× 10}{}^{\mathrm{?10}}\text{×}\text{M}{}^{0.50}{}_{\mathrm{<mtext>w</mtext>}}\text{(o-}\text{chlorophenol}\text{, 60.0°}\text{C}$

$\text{[ν] = 30.2}{}_4\text{× 10}{}^{\mathrm{?10}}\text{×}\text{M}{}^{0.50}{}_{\mathrm{<mtext>w</mtext>}}\text{(p-}\text{chloro}\text{-m}\text{cresol}\text{, 112.9°}\text{C}$

The characteristic ratio C_∞ = 〈R²〉₀/nl² was found to be 16.6 in o-chlorophenol at 60.0°C and 17.6 in p-chloro-m-cresol at 112.9°C. The value of the characteristic ratio C_∞ of PVK-3,6-Br₂ is of the same order of that for poly(N-vinyl carbazole). This indicates that the bromine atoms at the 3 and 6 (meta) positions have only an inappreciable effect on the hindering potential for rotation about the CC bond. This agreement of C_∞ for both polymers may also be taken as indicating that the effect of interaction between polar groups at the m-position on the hindering potential for rotation is small. The phase diagrams of PVK-3,6-Br₂ obtained in o-dichlorobenzene and bromobenzene seem to be characteristic of organized phase structures such as those found in systems exhibiting thermoreversible gelation. Light scattering measurement on PVK-3,6-Br₂ dissolved in o-dichlorobenzene, a gelation promoting solvent, and tetrahydrofuran, a very good solvent, strongly indicate that the macromolecular species in o-dichlorobenzene contain some extent supermolecular structures (aggregates, association of chain segments, etc.). These characteristic structures of PVK-3,6-Br₂ in o-dichlorobenzene and bromobenzene at 25°C are also characterized by high values of the Huggins' constant k′; for tetrahydrofuran solutions, the k′ values were in the range normally found for many good solvent-polymer systems.     

AB-initio studies of N-O-F compounds. Internal rotation in hydroxylamine and its fluorinated derivatives

Ab-initio molecular orbital theory at both the minimal and extended basis set levels have been applied to the study of internal rotation in hydroxylamine and its fluorinated derivatives. The computed energies are analyzed in terms of a Fourier-type expansion of the potential function. The total potential function V(φ)can be dissected into onefold (V₁), twofold (V₂) and threefold (V₃) components and plots of these components together with V(φ) are given for each of the molecules studied herein. Additionally geometry optimizations have been carried out as a function of the internal rotation angle φ (φ = : NOX dihedral angle) for H₂NOH and F₂NOF. For H₂NOH geometry optimizations are found to be less important than for F₂NOF. In general the fluorinated hydroxylamines prefer a $\text{trans}$-conformation (φ = 180°) while hydroxylamine itself adopts the $\text{cis}$-conformation (φ = 0°) largely as a result of a lower dipole interaction (V₁ term) in the $\text{cis}$-conformation.     

Organolanthanoids : II. Preparation and identification of some organolanthanoid species in solution

The organolanthanoid derivatives R₂M (R  C₆F₅, M  Yb or Eu; R  $\text{o}$-HC₆F₄ or PhCC, M  Yb) have been prepared by reaction of the corresponding diorganomercury compounds with ytterbium or europium metal in tetrahydrofuran at room temperature, and ($\text{o}$-HC₆F₄)₂Yb has been obtained by an analogous reaction at 0°C. The compounds were identified by determination of the amounts of polyfluoroarene or phenylacetylene and lanthanoid ions formed on acidolysis of the filtered reaction mixtures. Reaction of samarium with bis(pentafluorophenyl)mercury and of ytterbium with bis(2,3,4,5-tetrafluorophenyl) mercury at room temperature gives more complex products including RMF₂, MF₂ and RMF derivatives (R  C₆F₅, M  Sm; R  $\text{o}$-HC₆F₄, M  Yb), polyfluoropolyphenyls, and more complex organometallic species. These are considered to be derived from decomposition of initially formed (C₆F₅)₂Sm, (C₆F₅)₃Sm, and ($\text{o}$-HC₆f₄)₂Yb derivatives. The decomposition paths include fluoride elimination to give polyfluorobenzynes, reduction of polyfluoroaryl groups by lanthanoid(II) species, and hydrogen abstraction from tetrahydrofuran.     

High-pressure/high-temperature phase relations and vibrational spectra of CsSbF6

CsSbF₆(II) under ambient conditions is trigonal, space group $\text{D}{}_{\mathrm{3d}}{}^5\text{-R}\text{3}\text{m}$. At 187.8°C it undergoes a phase transition with an enthalpy change of 5.267 ± 0.316 kJ mole^?1, to phase CsSbF₆(I). CsSbF₆ decomposes with loss of fluorine at atmospheric pressure at high temperatures, but under pressure the decomposition is prevented and a melting point of 310°C at atmospheric pressure can be inferred. The $\text{II}\text{I}$ phase boundary and melting curve were studied as functions of pressure. The infrared and Raman spectra of CsSbF₆(II) were studied in the temperature range of ?256 to 20°C, at ambient pressure. The crystal chemistry of the CsSbF₆ and its relationship with other related compounds is discussed.     

Comparative reactions between aziridines and F2, COF2, CF3OF

In CFCl₃, aziridines $\text{I}$ react with F₂(6 %/N₂,  20°C), COF₂ (20 %/N₂,  40°C) and CF₃OF [1] (20 %/N₂,  40°C).Substitution products are obtained : l-(aziridine)carbonyl fluorides $\text{II}$ and l-Fluoroaziridines $\text{III}$

In (Et)₂O, aziridines $\text{I}$ react with COF₂ (20 %/N₂, 10°C) and we have the carbonyl fluorides $\text{IV}$.

Products IV can be thermally decomposed into β fluoro isocyanates.In CFCl₃, N substituted aziridines $\text{V}$ react with F₂(6%/N₂, 20°C) and with CF₃OF [2] (20%/N₂, 40°C). No reaction is observed with COF₂in our conditions (5% to 25%/N₂, 80°C to + 40°C).Addition products are obtained : N Fluoro amines β fluorinated $\text{VI}$, N Fluoro and NN difluoro amines β trifluoro methoxylated $\text{VII}$ and $\text{VIII}$.

with R = SO₂Ø, COØNO₂, Cl.     

Studies with dithizone: Part XXI. The Relationship between pH12 and Molar Solubility

The effect of changes of ionic strength on the partition of an analytically important weak acid between a variety of aqueous and immiscible organic phases has been studied with respect to new measurements on dithizone (3-mercapto-1,5-diphenylformazan) and di(p-tolyl)thiocarbazone. A linear relationship has been deduced between the pH at which 50% extraction takes place and S_r,o (the solubility of the reactant in the organic phase), and confirmed by measurements of pH_{$\text{1}\text{2}$}, and S_r,o for a large number of organic solvents. The solubilities of the reagents in water, S_r, are also reported. The form of the relationship between pH and log D, and between pH_{$\text{1}\text{2}$} and log S_r,o is the same whether a solution of dithizone consists of a single species or a mixture of thiol and thione forms in tautomeric equilibrium.     

Solid state chemistry of organic polyvalent iodine compounds. III. The crystal structures of 3-oxo-3H-2,1-benzoxiodol-1-yl m-chlorobenzoate (two polymorphs) and its isostructural derivative, 3-oxo-3H-2,1-benzoxiodol-1-yl benzoate

Two polymorphic modifications (IIα and IIβ) of 3-oxo-3H-2,1-benzoxiodol-1-yl m-chlorobenzoate (C₁₄H₈O₄ClI) have been obtained through crystallizations from a variety of solvents but neither crystal structure is formed at room temperature during the various topotactic transformations of the isomeric 2-iodo-3′-chlorodibenzoyl peroxide crystal structure (the crystalline peroxide topotactically isomerizes to IIα at ～65°C). Single-crystal X-ray diffraction analyses have shown that the fundamental structural motif of the acicular (α) crystal structure (a = 6.376, b = 10.547, c = 20.066 Å, β = 92.0°, $\text{z = 4,}\text{P2}{}_1\text{n}$) consists of two molecules mutually associated through two strong intermolecular I … O coordination bonds; the other polymorph (a = 5.057, b = 13.035, c = 10.339 Å, β = 99.5°, z = 2, Pc) was investigated only in (100) projection where it appears that a chlorine rather than an oxygen atom is intermolecularly coordinated to the trivalent iodine. Although these coordination modes suggest a structural analogy of IIα and IIβ with the two known crystal structures of 3-oxo-3H-2,1-benzoxiodol-1-yl o-iodobenzoate [one of which is formed in the facile topotactic isomerization of bis-(o-iodobenzoyl)peroxide at ～22°C], several differences are evident in their molecular conformations and packing modes.The only crystalline modification of 3-oxo-3H-2,1-benzoxiodol-1-yl benzoate, obtained from solvent crystallizations, is isostructural with IIα.     

Comparative hammett studies of imidoyl,benzylic, aldehydic hydrogens transfer and related reaction by t-butoxyl radical

The polar transition states involved in the hydrogen transfer reactions of N-benzylideneanilines, toluenes, benzaldehydes, and anisoles by $\text{t}$-butoxyl radical in benzene at 130°C have been comparatively discussed in terms of the values of the ρ and the k_a^o/k_d.     

Crystal preparation and properties of cesium tin(II) trihalides

Synthesis methods for cesium tin(II) trihalides via aqueous solution and from the melts of anhydrous halides, which ensure freedom from oxidation and the effects of traces of water, are described. The halide compounds CsSnCl₃, CsSnBr₂Cl, CsSnBr₃, CsSnBr₂I, CsSnBrI₂, and CsSnI₃ all have the cubic perovskite structure at elevated temperatures, and all but the first two are good electrical conductors in this form. The growth of single crystals from the melt, and by vapor transport, is outlined.The ${}^{35}\text{Cl}$ nuclear quadrupole resonance spectrum of monoclinic CsSnCl₃ consists of three lines, with frequencies 9,799, 11.005, and 11.695 MHz at 25°C, confirming the presence of pyramidal SnCl₃^? ions in this structure. In CsSnBr₃, there is a single ${}^{81}\text{Br}$ nuclear quadrupole resonance line, with frequency 63.073 MHz at 25°C, which splits into two lines on cooling the sample below 19°C. The low-temperature form of CsSnBr₃ apparently has a tetragonally distorted perovskite structure, with a = 11.59 and c = 11.61 Å at 12°C. A single ${}^{127}\text{I}$ nuclear quadrupole resonance line was observed in the low temperature orthorhombic form of CsSnI₃, with frequency 79.707 MHz at 25°C, and the variation of the frequency of this line with temperature may indicate a minor phase change in CsSnI₃ at 35°C.     

Synthesis and crystal structure of a π-allyl iron carbonyl complex derived from a fluorocarbon containing ligand by loss of fluorine

The β-chlorovinylphosphines R₂P$\text{C  CCl(C}$F₂)₃ (R = C₆H₅, C₆H₁₁) react with Fe(CO)₅ yielding compounds of stoichiometry

. The crystal structure of one of these (R = C₆H₁₁) has been determined from X-ray diffraction data and refined by least-squares to $\text{R}$ = 0.037 (2313 reflections with $\text{I}$ > 2.3σ_$\text{I}$). Crystals are triclinic, space group $\text{P}$$\text{1}$, $\text{a}$ = 10.253(5), $\text{b}$ = 15.590(7), $\text{c}$ = 9.390(4)Å, α = 99.88(3), β = 103.21(2), γ = 92.02(2)°, $\text{Z}$ = 2. The fluorinated π-allyl group is σ-bonded to one Fe atom and π-bonded to the other.     

The enthalpies of formation of bis-(benzene)molybdenum and of bis-(toluene)tungsten

Microcalorimetric measurements at 520–523 K of the heats of thermal decomposition and of iodination of bis-(benzene)molybdenum and of bis-(toluene)tungsten have led to the values (kJ mol^?): ΔH^o_f[Mo(η-C₆H₆)₂, c] = (235.3 ± 8) and ΔH^o_f[W(η⁶-C₇H₈)₂, c] = (242.2 ± 8) for the standard enthalpies of formation at 25°C. The corresponding ΔH^o_f(g) values, using available and estimated enthalpies of sublimation, are (329.9 ± 11) and 352.2 ± 11) respectively, from which the metalligand mean bond-dissociation enthalpies, $\text{D}$(Mo—benzene) = (247.0 ± 6) and $\text{D}$(W—toluene) = (304.0 ± 6) kJ mol^?1, are derived.     

Thermodynamic studies of the phase relationships of nonstoichiometric cerium oxides at higher temperatures

Partial molar thermodynamic quantities for oxygen in nonstoichiometric cerium oxides were determined by thermogravimetric analysis in $\text{CO}\text{CO}{}_2$ mixtures in the temperature range 900–1400°C. Under these conditions compositions within the range $\text{2.00 ?}\text{O}\text{M}\text{? ～1.75}$ could be obtained. A detailed analysis of the data shows that the α′-phase region in the phase diagram, previously described as a grossly nonstoichiometric phase, can be divided into several subregions each consisting of an apparent nonstoichiometric single phase. The finer details of the thermodynamic data, however, suggest that some of these subregions can be further split into ordered intermediate phases with compositions following the series M_nO_2n?2.Supplementary high-temperature X-ray diffraction studies under vacuum were made at temperatures up to 855°C. At the higher temperatures between 790 and 855°C, a new phase of low symmetry was obtained. Indexing of the powder pattern for this phase showed it to be isostructural with Pr₆O₁₁ and with a monoclinic unit cell with a = 6.781 ± 0.006Å, b = 11.893 ± 0.009 Å, c = 15.823 ± 0.015 Å, and β = 125.04 ± 0.04°.     

Molecular structure and conformation of cis-1,3- dichloro-1-propene as determined by gas phase electron diffraction

The molecular structure and conformation of cis-1,3-dichloro-1-propene have been determined by gas phase electron diffraction at a nozzle temperature of 90°C. The molecule exists in a form in which the chlorine atom of the methyl group and the carbon-carbon double bond are gauche to one another. The results for the distance (r_g) and angle (∠_α) parameters are: r(C-H) = 1.078(10)Å, r(CC) = 1.340(5)Å, r(C-C) = 1.508(7)Å, r( =C-Cl) = 1.762(3)Å, r(C-Cl) = 1.806(3)Å, ∠Cl-C-C = 111.7°(1.8), ∠(CC-C) = 125.5°(1.5), ∠Cl-CC = 124.6°(1.6) and ∠H-C-Cl = 111°(5). The torsion-sensitive distances close to the gauche form can be approximated using a dynamic model with a quartic double minimum potential function of the form V(Φ) = V₀[1 + ($\text{Φ}\text{Φ}{}_0$⁴ - 2($\text{Φ}\text{Φ}{}_0$)²], where V_o = 1.1(8) kcal mol^?1 and Φ₀ = 56°(5) (Φ = 0 corresponds to the anti form).     

Solid state reactions to CdTeMoO6 and its structural characterization

CdTeMoO₆ has been obtained by solid state reactions of CdMoO₄ with orth. TeO₂ at 425°C, with tetr. TeO₂ at 470°C, and with H₆TeO₆ at 490°C. Its crystal structure belongs to the tetragonal system (space group $\text{P4}\text{n}$ or $\text{P4}\text{nmm}$ with unit cell dimensions a = 5.279(2) Å, c = 9.056(2) Å. The specificity of this compound in the allylic oxidation reactions should be strictly related to its structural features, among which the presence of cis MoO₂ groups could be very important.     

The reaction of trihydrobistriphenylphosphine iridium IrH3(PPh3)2 with diazonium salts

The reaction of IrH₃(PPh₃)₂ with p-substituted aryldiazonium salts gives the compounds [IrH₂(NHNC₆H₄R)(PPh₃)₂]⁺BF₄^- at low temperature (-10°C) and the o-metalated complexes [I$\text{rH(NHN}$C₆H₃R)(PPh₃)₂]⁺BF₄^- (R  F, OCH₃) at 40–50°C. The reactions of the o-metalated complexes with CO, PPh₃, NaI and HCl have been studied.     

Substituent influence on the indolization with pcl3 of some o,m,p-substituted phenylhydrazones

The indolization of deoxybenzoin $\text{o}$,$\text{m}$,$\text{p}$ (Me, MeO, Cl), $\text{p}$-NO₂ and $\text{m}$-EtO-phenylhydrazones (1) by the above reaction has been examined. All the reactions are carried out at room temperature and high yields of the corresponding indoles (2) are obtained even when -NO₂ substituent is present. In this case longer reaction time is necessary. Alkoxyphenylhydrazones give the corresponding indoles (2) in high yields without showing collateral reactions which indeed are present in several Fischer routes on these derivatives. $\text{m}$-Substituted phenylhydrazones (1) give a mixture of 4- and 6-substituted indoles in which the 6-isomer is always prevalent, a feature not inherent in the Fischer reactions. The regioselectivity is enhanced by the substituent steric hindrance increasing. The reaction can be also carried out at 0°C with a further improvement of its regioselectivity.     

Molecular and electronic structure of the dehydroalanine derivatives: The cyclic dipeptide of dehydrophenylalanine

The molecular structure of the cyclic dipeptide of dehydrophenylalanine [3,6-bis(phenylmethylene)-piperazine-2,5-dione] has been determined from three dimensional X-ray data. C₁₈H₁₄ N₂O₂ is monoclinic, space group C2/$\text{c}$, with Z = 12 in a cell of dimensions $\text{a}$=4Ø.774(1), $\text{b}$=6.237(2), $\text{c}$=17.731(3) Å, β=107.76(5)°. Molecules are approximately planar as far as the piperazinedione ring is concerned, and they are linked in two series of hydrogen-bonded ribbons. The vapour phase He(I) and He(II) photoelectron spectra are also presented. Their assignment is proposed by comparison with related molecules and supported by semiempirical quantum mechanical calculations. Analogies and differences with respect to the photoelectron results of the cyclic dipeptide of dehydroalanine and corresponding acyclic compounds are discussed.     

Organomercury compounds XX Reactions of lithium polyfluorobenzenesulphinates with mercuric salts

The lithium polyfluorobenzenesulphinates, Li O₂SR (R = C₆F₅, $\text{p}$-HC₆F₄, $\text{m}$-HC₆F₄, or $\text{o}$-HC₆F₄), and the dilithium tetrafluorobenzenedisulphinates, $\text{p}$- and $\text{o}$-(LiO₂S)₂C₆F₄, have been prepared by reaction of the appropriate polyfluoroaryllithium compounds with sulphur dioxide. All compounds were isolated as hydrates and gave the corresponding $\text{S}$-benzylthiouronium salts on treatment with $\text{S}$-benzylthiouronium chloride. From reactions of the lithium sulphinates with suitable mercuric salts in water, generally at room temperature, the derivatives RHgX (R = C₆F₅, X = Cl, Br, CH₃CO₂, or PhSO₂; R = $\text{p}$-HC₆F₄, X = Cl, Br, or CH₃CO₂; R = $\text{m}$-HC₆F₄, X = Cl or Br; R = $\text{o}$-HC₆F₄, X = Cl), $\text{p}$-(XHg)₂C₆F₄ (X = Cl, Br, or CH₃CO₂), and $\text{o}$-(XHg)₂C₆X₄ (X = Cl or Br) have been prepared. Similarly, the bispolyfluorophenylmercurials R₂Hg (R = C₆F₅, $\text{p}$-HC₆F₄, or $\text{m}$-HC₆F₄) have been prepared from the corresponding lithium sulphinates and either mercuric salts or polyfluorophenylmercuric halides in aqueous $\text{t}$-butanol. A possible mechanism for the sulphur dioxide elimination reactions is discussed.     

Chemistry of fluorinated quinones. Part II proton and fluorine nmr spectra

Proton and fluorine NMR spectra of nineteen fluorinated quinones are presented. Coupling constants were found for HH: $\text{o}$ 10.5, $\text{m}$ 2.2, $\text{p}$ ?0.3-0; for FF: $\text{o}$ 4.5–5.6, $\text{m}$ 0.3–1.7, $\text{p}$1.5–3.0; and HF: $\text{o}$ 8.2–10.1, $\text{m}$ 6.0–8.4, and $\text{p}$ 0.6–0.9.