Decomposition Thermique du Dimanganese Decacarbonyle et du Dirhenium Decacarbonyle

The thermal behaviours of dimanganese decacarbonyl and dirhenium decacarbonyl were studied by TG, DTG and DTA. The decomposition products in different media were identified by X ray diffraction. In an inert medium, no important difference is observed between the two compounds. In an oxidizing medium, the identified products at 350? are a mixture of MnO andγ-Mn₂O₃ for the manganese compound and ReO₃ for that of Re. The decomposition temperatures of these metal carbonyls are functions of the studied medium. According to studies of metal-metal bond dissociation energies, Mn₂(CO)₁₀ is less stable than Re₂(CO)₁₀.     

Composes chiraux du zirconium et du hafnium

The first chiral dicyclopentadienyl compounds of zirconium (IV) and hafnium(IV) of the form (η⁵-C₅H₅) (η⁵-RC₅H₄)MClX (X = alkoxy, aryloxy or benzyl group) have been prepared and studied. The presence of an asymmetric metal atom is shown by NMR of these complexes containing suitable ligands.     

Nouveau dosage volumétrique du cuivre au moyen du dichromate

A method for the determination of copper by cuprous thiocyanate is described. This is effected by reacting with ferric sulphate: 3CuCNS +2Fe(S0₄)₃→Fe(CNS)₃ + 3FeSO₄ + 3CuSO₄The determination of Fe′ with dichromate in presence of thiocyanate by means of mercuric sulphate or nitrate was first investigated, and when this had been established, the Fe′ produced according to the above reaction (and which is stoichiometrically equivalent to the amount of copper present), was determined. Very satisfactory results were obtained.     

Polymorphisme du tetrachloro-1,2,4,5 benzene et du tetrabromo-1,2,4,5 benzene

Combination of three techniques of thermal analysis (hot stage polarising microscope, DSC, Guinier-Lenne) enabled the determination of the polymorphic behaviour of tetra 1,2,4,5-X benzene (X=Cl, Br). Thermal, calorimetric and crystallographic characterizations have been carried out. This study puts forward an interesting problem: theβ phase (P2₁/a, stable at room temperature) of the tetra chlorobenzene has similar arrangement to the two solid piases P2₁/a of tetra bromobenzene. Which one of these two forms is actually isomorphic with tetra chlorobenzene.     

Etude par RMN du 13C d'un heterocycle derive du dibora-2,4 diazaro-1,3 benzene et du borazine correspondant

¹³C NMR spectra and complete assignment by means of coupled spectra and off resonance experiments, are reported for a new kind of organoboron heterocycle and the related borazine (o-CH₃C₆H₄NBCH₃)₃; π-charge densities, obtained from LCAO-MO Hückel calculations, are in reasonable agreement with experimental chemical shifts for the former compound.     

Dosage du molybdene et du tungstene dans les plantes par activation neutronique

A method for the determination of molybdenum and tungsten in plant material using neutron activation analysis was developed. The considered reaction are: $$\begin{gathered} {}^{98}Mo(n,\gamma )^{99} Mo \hfill \\ {}^{186}W(n,\gamma )^{187} W \hfill \\ \end{gathered} $$ The separation for tungsten and molybdenum was carried out using anion exchange separation (Dowex 1×10; 200–400 mesh). Irradiation was carried out in a swimming pool reactor at a thermal flux of about 1–2×10¹³ n·cm^?2·sec^?1 for 15 hours. The samples and standard were allowed to cool for 5–6 hours before chemical processing. the high concentration of calcium in plants (up to 40 mg/g dry material), the use of hydrofluoric acid for a good absorption and quantitative recovery of tungsten led us to dissolve the samples with Ht?H₂O₂ mixtures containing boric acid to prevent the precipitation of fluorides.     

Influence du silicium et du germanium sur l'ene-reaction-comportement inattendu des allenylsilanes

The determining role of silicon and germanium for ene syntheses was confirmed in the reactions between 1-sila and 1-germacyclopent-3 enes or allenylsilanes and PhSO₂NSO, a highly reactive new enophile. In the case of the cyclic enes the reaction led to new α,β-unsaturated β-functional cyclic derivatives which can be easily reduced into the corresponding thiols. With allenylsilanes, the adducts resulting from the ene-reaction with PhSO₂NSO or 4-phenyl 1,2,4-triazoline 3,5-dione have an acetylene structure whereas the substituted allenes usually give conjugated diene derivatives.     

Telomerisation par catalyse redox—III. Etude de la reactivite des telogenes du type r-cc13, selon la nature du substituant r vis-a-vis du styrene

Among the various chloromethanes and chloroethanes, only compounds of the type R-CCl₃ are reactive telogens for styrene in catalysed telomerizations of the type due to Vofsi. We have found evidence for a new type of breakdown of CCl₃Br to CCI₂Br and CI in addition to the known breakdown to CC1₃ and Br'. A Hammet equation has been established for the telomerization involving styrene and telogens of the type RCCl₃. Excellent correlation has been found between the logarithm of the reactivity of a telogen and the Taft constant of the group R.     

Spectres de masse de phosphonates diméthyliques dérivés du norbornane,du norbornéne et du nortricyclane

The mass spectra of dimethyl phosphonates (I to X) derived from norbornane, norbornene and nortricyclene have been studied. The fragmentation of endo and exo isomers is quite similar (only the peak intensities vary a little) except for the saturated compounds I and II where the orientation of the P(O)(OCH₃)₂ group seems to exert an influence. The spectra of the norbornene derivatives III and IV and of the isomeric nortricyclic compound IX are quite different. The fragmentation pattern of all phosphonates I to X is dominated by the localisation of the charge on the phosphorus moiety.     

Etude viscosimetrique du systeme polystyrene-cyclohexane-acetone

Determinations of viscosities have been made on the polystyrene-cyclohexane-aceton system for various monodisperse polystyrene samples with molecular weights between 50000 and 870000 and for various compositions of cosolvent mixtures. The intrinsic viscosity (η), the parameters B and K_θ exhibit maximum values at the equimolecular composition which also corresponds to the maximum values of the thermodynamic excess functions. The variations of K_θ and B are discussed in terms of the binary interaction parameters χ_ij.     

Dosage polarographique de quelques constituants du verre

A method is described for the determination of the following constituents of glass: Na and K together, Ca, Ba, Al, Pb and Zn.The analysis is carried out on a solution from the glass prepared by dissolving it in HF + HClO₄. The alkali metals are determined in the presence of N(CH₃)₄OH + H₃PO₄, and barium in the presence of N(CH₃)₄OH only. Calcium is separated as oxalate, transformed into chloride and determined in the presence of N(CH₃)₄OH. Aluminium is polarographed in a solution of pH3 in the presence of LiCl and dimethyl yellow. Zinc is determined in the presence of NH₄Cl, and lead in the presence of NH₄Cl and methyl red.The relative influence of each constituent element of the glass is discussed and it is shown that there is good agreement between the gravimetric and polarographic methods.     

Isomerisation et polymerisation du cis-pentadiene-1,3

Cis-1,3-pentadiene can be polymerized in benzene solution by a catalyst formed from triethylaluminium and n-butylorthotitanate. When the molar ration Al/Ti is below 6, polymerization proceeds through a previous cis-trans isomerization of the diene. It has been possible to measure the two rate constants (k_t and k_p) which characterize the isomerization and the polymerization steps, respectively. The first one reaches its highest value when Al/Ti equals 2·6 and k_p is maximum when Al/Ti equals 6. Chloroform, which is a very efficient inhibitor for the polymerization, does not affect isomerization. Data are given on the microstructures of the polydienes so obtained.     

Recyclage du Cryptand (222)

Abstract

A novel recovery process for cryptand (222) based on the insolubility of the species (222)(HC10₄)₂ in methanol was described. It involved six successive operations and the global yield reached to 96%.     

Etude analytique par thermogravimetrie et analyse thermique differentielle du peroxyde de sodium hydrate et du peroxyde de sodium commercial

Thermogravimetry and differential thermal analysis were used to study hydrated sodium peroxide and the so-called anhydrous commercial product. Prolonged dehydration of the octahydrate under vacuum led to the partial formation of Na₂O₂-H₂O₂ compounds as well as the dihydrate and monohydrate The DTA curves for commercial sodium peroxide heated in air or other gases, showed the partial formation of Na₂O₂·2H₂O₂·nH₂O and of NaHCO₄·H₂O by the action of the gases on the NaO₂ contained in the Na₂O₂.     

Complexes du titane et du zirconium contenant les ligands cyclopentadienyldiphenylphosphine et cyclopentadienylethyldiphenylphosphine: acces a des structures heterobimetalliques

Reactions of Ph₂P(CH₂)_n(C₅H₄)Li, (n = 0, 2), with MCl₄ or CpTiCl₃ (M = Ti, Zr; Cp = η⁵-C₅H₅) form Cl₂M[(η⁵-C₅H₄)(CH₂)_nPPh₂]₂ or Cl₂CpTi[(η⁵-C₅H₄)-(CH₂)₂PPh₂] in good yields. Chemical reduction with Al, or electrochemical reduction of these complexes, under CO, are described. The titanium(IV) and zirconium(IV) derivatives react with metal carbonyls (Mo(CO)₆, Cr(CO)₆, Fe(CO)₅, Mo(CO)₄(C₈H₁₂)) under formation of new heterobimetallic complexes. Reduction with Al of Cl₂CpTi[(η⁵-C₅H₄)(CH₂)₂PPh₂]Mo(CO)₅ under CO results in a new heterobimetallic species containing low valent titanium. Both complexes Cl₂M[(η⁵-C₅H₄)(CH₂)₂PPh₂]₂ (M = Ti, Zr) react with [Rh(μ-Cl)(CO)(C₂H₄)]₂ to yield {RhCl(CO)(Cl₂M[(η⁵-C₅H₄)(CH₂)₂PPh₂]₂)}x, which is assumed to be a dimer, in which the titanium or the zirconium compounds act as bridging diphosphine ligands between the rhodium atoms.     

Heterocycles du germanium,du phosphore (III), de l'arsenic — (III) et du soufre a ligand aminoacide ou hydroxyacide

Two ways of obtaining germaoxooxaazaolodines and germaoxodioxaolanne are described. Exchange reactions between these derivatives and the dichlorides PhPCl₂, PhAsCl₂ SOCl₂ lead in good yield to the corresponding phosphorus(III), arsenic(III) and sulphur derivatives, these compounds being impossibly to prepare via any other route.     

Cycloaddition de derives organiques insatures du silicium,du germanium et de l'etain

The effect of atom M and of its substituents Σ upon dienophilic activity of Σ₃MCHCH₂ and Σ₃MCCH (MC, Si, Ge, Sn) is interpreted in terms of a perturbation scheme involving the lowest unoccupied orbital of the dienophile and the highest occupied orbital of the diene. This scheme also explains the stereochemistry of Diels-Alder reactions and the regioselectivity of the ene reaction with organometallic compounds.     

Etude du diagramme d’equilibre du systeme NaPO3−Pr(PO3)3

The NaPO₃?Pr(PO₃)₃ system was studied by microdifferential thermal analysis (DTA), IR and X-ray diffraction spectroscopies. The only new compound observed in the system is NaPr(PO₃)₄, which melts incongruently at 1149 K. A eutectic appears at 5% Pr(PO₃)₃ at 901 K. The new compound NaPr(PO₃)₄ was characterized by means of powder X-ray diffraction and IR absorption spectroscopy. NaPr(PO₃)₄ is a NaLa(PO₃)₄ isotype; it crystallizes in the monoclinic system P2₁/c witha=12.328(7),b=13.130(5),c=7.231(5) Å, β=126°, 18(5),Z=4,V=945 ?³.     

Telomerisation par catalyse redox—II. Telomerisation du styrene,de l'acrylonitrile,et du monochlorotrifluoroethylene par des telogenes chlores

A study has been made, under conditions for telomerization catalysed by a redox system, of the reactivities of styrene, acrylonitrile and monochlorotrifluoroethylene with respect to some telogens viz various chloroethanes, methyl trichloroacetate, CCl₂F.CClF₂ and CClF₂.CClF1. Generally, the selected catalyst system led only to products of monoaddition; these products were isolated and identified.     

Reaction du meta-diisopropyl-phenyllithium-chrometricarbonyle avec le monoxyde de carbone

The complex CpV(CO)₃THF has been prepared in THF solution (i) photochemically from CpV(CO)₄, and (ii) from [CpV(H)(CO)₃]^?/[Ph₃C]⁺ at low temperatures. THF is replaced by [CpV(H)(CO)₃]^? to form [{CpV(CO)₃}₂-μ-H]^?, and by various ligands L with C, η²-CC, Sn, N, O, S, Se or Te functionality to yield CpV(CO)₃L and cis-[CpV(CO)₂LL] (LL = bipy, o-phen, tolane). The δ (⁵¹V) values range over ca. 1400 ppm and allow the assignment of distinct coordination modes for ambidentate ligands. The temperature gradient is ca. +1.2 ppm/deg. For [CpV(SnCl₃)(CO)₃]^? (δ ?1340 ppm rel. to VOCl₃), ¹J(⁵¹V-^117,119Sn) is 900 Hz. The isotope effect on introducing ¹²CO for ¹³CO in CpV(CO)₄ is ?0.48(2) ppm; ¹J(⁵¹V-¹³C) 107 Hz.