Determination des constantes de dissociation ionique du chlorure de nitrosyle et de N2O4 dans le sulfolane

Determination of the ionic dissociation constants of nitrosyl chloride and dinitrogen tetroxide in sulpholane.

A silver chloride—silver electrode is used to study electrochemical systems involving nitrosyl chloride and dinitrogen tetroxide in sulpholane: Ag↓ + NOCl AgCl↓ + NO⁺ + e^- and Ag↓ + NOCl + NO^-₃ AgCl↓ + N₂O₄ + e^- The dissociation constants of these two NO⁺ donors determined in this way are: K_(NOCl) = 10^-11.8 mol l^-1 and K_(N2O4) = 10^-7.2 mol l^-1. A titration of N₂O⁴ solutions alone or in the presence of nitric acid is described. This titration is possible in mixtures which contain up to 90% (w/w) nitric acid.     

Interactions magnétiques dans des groupements binucléaires [Fe2O7]8− au sein de Na8Fe2O7

The magnetic interaction in the structural units [Fe₂O₇]^8?, built of two corner-sharing FeO₄ tetrahedra, in Na₈Fe₂O₇ ($\text{Na}{}_2\text{O}\text{Fe}{}_2\text{O}{}_3\text{=}\text{4}\text{1}$) has been studied by magnetic susceptibility measurements (4.2–500 K). An exchange integral $\text{J}\text{K}{}_{\mathrm{<mtext>B</mtext>}}$ of ?37 K is obtained by comparison of the experimental values and the calculated ones using a Heisenberg-Dirac-Van Vleck-type Hamiltonian ? = $\text{?2J}\text{S}\text{?}{}_1\text{S}\text{?}{}_2$. The hypothesis of magnetically isolated [Fe₂O₇]^8? groups is corroborated by Mössbauer spectroscopy between 1.5 and 77 K. The susceptibility measurements of the solid solutions Na₈Fe_2?xM_xO₇ (M = Al, Ga; 0 ≤ x ≤ 0.2 for Al; 0 ≤ x ≤ 2 for Ga) leads to the same conclusion of the existence of isolated Fe³⁺Fe³⁺ pairs in Na₈Fe₂O₇. The type of substitution of Fe by Al or Ga is determined; homonuclear Fe³⁺Fe³⁺ and M³⁺M³⁺ pairs and heteronuclear Fe³⁺M³⁺ pairs are formed.     

Insertion reactions of thermally generated stannylenes R2Sn into Sn-X (X = Cl,Br, SPh) and Sn-Sn bonds

Thermally generated stannylenes R₂Sn insert efficiently into Sn-X bonds (X  Cl, 3r, SPh) as well as into electron deficient SnSn bonds e.g. in Me₂(Hal)SnSn(Hal)Me₂, but not into hexaalkyldistannanes R₆Sn₂ under the same conditions; stannylenes R₂Sn always behave as nucleophiles here.     

Etude spectroscopique du role des liaisons PF et PO pontes dans les composes oxyfluores du phosphore V. Cas de P2O3F4 et de K2P2O5F2.

The compounds P₂O₃F₄ and K₂P₂O₅F₂ have been studied by vibrational spectroscopy. From the shifts of the symmetric vibration of the terminal PO bonds it appears that the molecular structure contracts as the number of PO (bridged) and/or PF bonds increases. The changes occur at the expense of PO terminal bonds. In these tetrahedral phosphorus (V) compounds the PO (bridged) and PF bonding have a similar role, and the same phenomenon occurs in sulfur VI oxide fluoride compounds.     

Etude de la structure K2NiF4 par la méthode des invariants,I. Cas des oxydes A2BO4

The study of the K₂NiF₄ structure by the “method of invariants” leads to the relationship

$\text{0.99615 V}\text{1}\text{3}\text{=β}{}_{\mathrm{B}}\text{+ψ}{}_{\mathrm{A}}\text{2}\text{1}\text{2}$

with V = a²c (β_B and ψ_A are invariant values associated with cations B and A) in compounds with K₂NiF₄ structures. Some values of ψ_A and examples are proposed.     

Spectres de vibration des molecules BCl2CO et BX2NCS (X = Cl,Br, I), champs de forces et modes normaux

Experimental data on the vibrational spectra of BX₂¹⁴NCS (X = Cl, Br or I), BCl₂¹⁵NCS, BBr₂¹⁵NCS, and BCl₂NCO are reported. Analysis of the results shows that the boron atom is bonded to the nitrogen atom, and the BN, CN, CS and CO bonds are colinear. Force fields are calculated and found to reproduce the experimental frequencies and the ¹⁰B-¹¹B and ₁₄N-₁₅N isotopic effects. High values are obtained for the force constant of the B-N stretching vibration (about 6.5 mdyn Å^?1) and it is shown that, owing to electron transfer from nitrogen to boron, the B-N bond is intermediate between a single and a double bond. The force constant νBX is marginally greater than that for the corresponding BX₂SH compounds. The C-N bond is weaker than in the NCS ion, whereas the CS bond is stronger.Calculation of the normal modes and the potential energy distribution shows that for the BCl₂NCO molecule, the B, N, C, and O atoms are almost equally involved in all the modes of A, symmetry, especially those at 2270, 1525 and 1022 cm^?1. On the other hand, for BX₂NCS compounds, the potential energy is relatively localised on one coordinate. Consequently, the group vibration approximation is justified in this case.     

Evolution des tenseurs de dilatation thermique en fonction de la température. III. Etude expérimentale des oxydes PbO1,57, PbWO4, V2O5 et V2O3 et analyse des résultats

The evolution of thermal expansion tensor versus temperature has been measured by powder X-ray diffraction for PbO_1,57 (in the range 77–636°K), PbWO₄ (95–800°K), V₂O₅ (77–773°K) and V₂O₃ (77–600°K). Tensor anisotropy is explained considering structure and chemical bonds (V₂O₅, PbWO₄). We verified that the evolution of anisotropy (measured by aspherism index) is much different, according to whether the oxide presents a continuous phase transition (V₂O₃) or not (PbO_1,57, PbWO₄, V₂O₅).     

Structure cristalline de NaSbF3NO3·H2O. Etude de la liaison hydrogene OHX (X = Cl,Br, NO3)

NaSbF₃NO₃·H₂O compound has been isolated in the SbF₃NaNO₃H₂O system. The crystal structure was determined by X-ray diffraction on a single crystal. The final R factor is 0.044. The structure is compared with those of NaSbF₃X·H₂O (X = Cl, Br). The hydrogen bonds OH…X (X = Cl, Br, NO₃) form the subject of a vibrational spectroscopic study.     

Etude comparative des composés TiX2 (X = S,Se, Te). Structures de TiTe2 et TiSeTe

The evolution of crystal-structure and chemical-bond characteristics is studied for the series of isotypical compounds TiX₂, with X = S, Se, Te. The structure determination of TiTe₂ and TiSeTe confirms the existence of an increasing trigonal C_3v distortion of metal sites when the chalcogen electronegativity decreases. The ESCA study shows that this distortion is associated with augmentation of the covalent or metallic character of the bonds. The structural and spectroscopic differences appearing from TiS₂ to TiSe₂ can be interpreted by an orbital delocalization in TiSe₂ and TiTe₂, which would explain the semimetallic behavior of these compounds.     

Influences des entraîneurs Ga2O3 et NaF sur la volatilisation et l'excitation du vanadium dans la methode de Scribner—Mullin

A study has been made of the effect of NaF and Ga₂O₃ as entrainers, on the spectral line intensities of vanadium, and on the sensitivity and detection limits by the Scribner-Mullin method. The two entrainers have different effects on the volatilization of vanadium. By radiotracer methods with ⁴⁸V, the degree of volatilization was found to be 37% with NaF and 0·9% with Ga₂O₃. Use of NaF greatly increases the sensitivity, lowering the detection limit by a factor of about 50, without affecting the precision. The physicochemical conditions in the plasma do not seem to influence the line intensities with either entrainer.     

Etude de la reaction de (MClcod)2 (M = Ir,Rh) avec les coordinats PClxPh3-x dans CDCl3

An NMR study of the reaction of (MClcod)₂ (M = Ir, Rh; cod = 1,5-cyclo-octadiene) with the ligands PCl_xPh_3-x, has been developed. Except when x = 3 we obtained as the first step the complex MClcod(PCl_xPh_3-x). This compound reacted with an excess of phosphine if x = 1 or 2, to give the complex MCl-(PCl_xPh_3-x)₃. However if M = Ir we have shown the formation of an intermediate species IrClcod(PCl_xPh_3-x)₂. We have studied the kinetics of the reaction:

When x = 3, we obtained the complexes (IrClcod)₂(PCl₃) and (IrClcod)₂(PCl₃)₃, for which we propose the structures.     

Etudes par spectroscopie dans l'ultra-violet et le visible, du fullerène C60 en solution dans le n-hexane ou adsorbé sur des solides diélectriques

Ultraviolet and visible spectroscopy studies of the fullerene C₆₀ melted in n-hexane or adsorbed on dielectric solids. Experiments of spectroscopy have been carried out, between the far ultraviolet and the near infrared, with pure C₆₀ or containing endohedral complexes rare gas atom-C₆₀, melted in n-hexane, and also pure C₆₀ adsorbed on surfaces of solids.Several phenomena have been observed: 1. a charge transfer due to the influence of interactions between the molecules of C₆₀ and surfaces of solids, yielding new transitions observed in the far ultraviolet ; and interpreted as super excited states of Rydberg type; 1.1. red and blue shifts for some transitions of adsorbed C₆₀, interpreted on the basis of attractive, or turned repulsive, dispersion forces; 1.1.1. emission processes for several transitions of adsorbed C₆₀, explained on the basis of a resonant coupling between these transitions and modes of the surface plasmon induced by the collective excitations of the C₆₀ molecule; this kind of process might be drawn to the Faraday instability in acoustics.     

Etude par RMN de la mobilité du lithium dans trois oxydes à structure pseudo-bidimensionnelle: Li8SnO6, Li7NbO6 et Li6In2O6

The lithium ion mobility in three solid electrolytes (Li₈SnO₆, Li₇NbO₆, and Li₆In₂O₆) has been studied by NMR at several resonance frequencies from 170 to 500°K. The ⁷Li quadrupolar lineshape evolution shows the predominant influence on the conductivity mechanism of the vacancies in the octahedral sites of the oxygen close packing. In Li₈SnO₆, which has no vacancies, the lithium ions situated in the tetrahedral sites have the highest mobility. Spin-lattice relaxation times are in good agreement with the hypothesis of a Li₇NbO₆ 2D conductivity. The values of the activation energy, increasing from Li₇NbO₆ to Li₆In₂O₆ and to Li₈SnO₆, are found to be three times lower than those obtained from conductivity measurements.     

Etude par diffraction X et par spectrometrie de vibration de composes de coordination des halogenures d'aluminium avec l,acetonitrile: analyse vibrationnelle des cations AlCl(CH3CN)2+5 et AlBr(CH3CN)52+

The compounds AlX₃-2CH₃CN and AlX₃-1.66CH₃CN (X = Cl, Br) are prepared in order to study the vibrational properties of AlX(CH₃CN)²⁺₅. The different chemical phases obtained are characterised by X-ray diffraction. It is shown that AlCl₃-2CH₃CN and AlBr₃-2CH₃CN are isomorphic and unit cell parameters are determined. The spectra of the cations AlX(CH₃CN)²⁺₅ in the 600-50cm^?1 range are interpreted by comparison with those of Al(CH₃CN)³⁺₆ and from the data obtained from H-D substitution. Analysis of the spectra of the complexes AlX₃-1,66CH₃CN enables the formula [2AlX^?₄: AlX(CH₃CN)|²⁺₅] to be postulated.     

Etude vibrationnelle des composes (C4H4P)Mn(CO)3 et [C4H2(CH3)2P]Mn(CO)3 et calcul du champ de force du cycle C4H4P complexe

The Raman and infrared spectra (4000200 cm^?1) of (C₄H₄P)Mn(CO)₃ and (C₄D₄P)Mn(CO)₃, and of [C₄H₂(CH₃)₂P]Mn(CO)₃ and [C₄D₂(CH₃)₂P]Mn(CO)₃ in the liquid and solid states (10–400 K) have been investigated. A complete vibrational assignment is proposed and valence force fields of the (C₅H₅) and (C₄H₄P) cycles are compared. From these results, it is clearly shown that the (C₄H₄P) rings are more electrophilic and weaker π-electron donors than (C₅H₅) rings, this is in agreement with their chemical behavior.     

Détermination du champ de force de valence des composés de coordination trans PdIIL2X2(L = (CH3)2S et (CD3)2S; X = Cl,Br et I) discussion de la structure moléculaire à partir des effets isotopiques du deuterium

A valence force field of the coordination compounds trans Pd[(CH₃)₂S]₂X₂ has been computed. This calculation is based on the infrared and Raman spectra of normal and perdeuterated complexes. The effect of geometry on isotopic shifts and values of the low vibrational frequencies indicates a distortion of the ligand around the PdS bond. The force constant of the coordination bond increases by 10 % when going from benzene solution to the solid state at 80 K.