Sels de cobalticinium : II. Proprietes spectroscopiques et polarographiques de quelques derives du cobalticinium

The spectroscopic and polarographic behaviour of some cobalticinium derivatives have been studied. Due to their positive charge these compounds exhibit particular characteristics in comparison with ferrocene derivatives. They give two successive cathodic waves on a dropping mercury electrode. The first corresponds to the formation of cobaltocene whereas the second represents the reduction of the latter compound to give cobaltocene anion.     

Alcoolyse et glycolyse de derives organozinciques et organocadmiens par des composes chiraux

The reaction between organozinc or organocadmium derivatives and different chiral hydroxy compounds leads to the corresponding alcoholates and glycolates which can be used as initiators in polymerizations.The composition of such initiators is defined by the ratio i_S = R-M-O/O-M-O of the number of alkylalkoxy groups to the number of dialkoxy groups. This ratio depends on the nature of the organometallic and hydroxy compound and on the conditions of reaction used to prepare them.Toward a given hydroxy compound, the reactivity of the organometallic derivatives follows the order: ZnEt₂ > CdEt₂ > CdMe₂.Primary alcohols and 1,2-diols are more reactive than secondary alcohols in the case of organozinc compounds, while in the case of organocadmium compounds the secondary alcohols are more reactive than primary alcohols, but less reactive than 1,2-diols. The kinetics of the reaction can be followed by monitoring the variation of optical activity of the solution.Several compounds having definite stoichiometry have been isolated and identified by their NMR spectra.     

Etude des aldimines lithiees : I. Synthese d'aldehydes ω-halogenes et de dialdehydes

Aldimines are conveniently metallated, at a position α to the functional group, by using very powerful bases i.e. activated lithium dialkylamides generated in situ from lithium and a secondary amine in benzene/hexamethylphosphoric triamide. The anions obtained are alkylated with various ω,ω′-dihalogenoalkanes to give, after aqueous acid hydrolysis, good yields of ω-halogenated aldehydes and dialdehydes.     

Reactifs de grignard vinyliques γ fonctionnels : II. Iodolyse,alkylation et arylation des iodo-alcools

Iodination of γ-functionally substituted vinylic Grignard reagents, prepared by addition of organomagnesium compounds to α-aactylenic or α-allenic alcohols gives vinyl iodides stereospecifically. Treatment of these iodides with Grignard reagents in the presence of (PPh₃)₂NiCl₂ gives allylic alcohols. This reaction proceeds with high stereoselectivity.     

Influence des impuretés sur la conductivité cationique dans l'oxyde de magnesium monocristallin

The measurement of the cationic transport numbers in MgO single crystals has been performed, using the dilatocoulometric method. In the oxygen partial pressure range 1 to 10^?10 atm at temperatures of 1100 to 1300°C the ionic conduction in MgO is extrinsic.     

A mechanistic investigation of the decacarbonyldimanganese-catalyzed carbonylation of amines

The Mn₂(CO)₁₀-catalyzed reactions of n-butylamine and cyclohexylamine with CO to give the corresponding ureas have been examined under a variety of conditions of temperature, CO pressure, reaction time, solvent and potential co-catalysts. With the diamines, ethylenediamine and 1,4-diaminobutane, there was no catalyzed reaction with CO. On the other hand, 1,3-diaminopropane gave 1,4,5,6-tetrahydropyrimidine, and 1,6-diaminohexane yielded a polyurea. In an effort to elucidate the mechanism of these reactions, several stoichiometric reactions were carried out. The reaction of Mn₂(CO)₁₀ with primary aliphatic amines proceeds to give a carbamoyl complex as follows: Mn₂(CO)₁₀ + 3 RNH₂ ? cis-Mn(CO)₄(NH₂R)(CONHR) + RNH₃⁺ + Mn(CO)₅^? Under CO pressure the isolated carbamoyl complex reacted to give the urea as follows: cis-Mn(CO)₄(NH₂R)(CONHR) + CO → (RNH)₂CO + HMn(CO)₅ The mechanism of this latter reaction is proposed to involve the intermediate formation of the organic isocyanate RNCO. These reactions are discussed as part of an overall mechanism for the Mn₂(CO)₁₀-catalyzed formation of ureas. The mechanism successfully accounts for factors which affect the yields of the reaction. Other metal carbonyl complexes, Re₂(CO)₁₀, (η-CH₃C₅H₄)Mn(CO)₃ and [η-C₅H₅Cr(CO)₃]₂, did not catalyze the reactions.     

Microdetermination of secondary aliphatic amines using a copper ion-selective electrode

A simple, accurate, and selective method is described for the microdetermination of aliphatic secondary amines. The method is based on their reaction with carbon disulfide and ammoniacal copper sulfate at 40 °C for 30 min to yield copper dialkyldithiocarbamate. The excess copper is then measured by titration with EDTA or NaDDC using a copper ion-selective electrode. A mean recovery of 98.2% with a standard deviation of 0.8% is obtained for aliphatic secondary amines and their salts having a wide range of pK_a.     

Etude thermochimique de quelques benzoates de cuivre(II) solvates

Some compounds of copper(II) benzoate solvated by ligands containing either oxygen (water, alcohol, dioxan) or nitrogen (amines, amides) or both, have been prepared. The thermal decomposition has been studied by TG and ATD methods. The standard enthalpies of formation have been determined and verified by some estimation methods.     

Reaktionen von carbonylcyclopentadienylhydriden des molybdäns und des wolframs mit inaminen

The hydrides (η⁵-C₅H₅)(CO)₃MH (M = Mo, W) react with ynamines R′CCNR₂ under mild conditions to form 1 : 1 adducts. According to the ¹H and ¹³C NMR spectra depending on the metal and the ynamine substituents carbene acyl chelate or complexes with η³-aminoacryloyl ligands are formed:

A Dicarbene chelate compound is obtained by alkylation of I, R = Et, R′ = Me. CC-η² keteneimmonium complexes are formed in the reaction of the phosphite substituted hydrides (η⁵-C₅H₅)(CO)₂P(OMe)₃MH (M = Mo, W) with MeCCN Et; an intermediate 1-aminovinyl compound has been isolated.     

L'addition des organomagnesiens aliphatiques satures sur les triples liaisons disubstituees non conjuguees: IV. Influence d'un groupement fonctionnel thioether en α de la triple liaison. Action catalytique du cuivre

The addition reaction of ethylmagnesium bromide to the triple bond of the compounds of general formula EtSCH₂CCCH₂Y (where Y is the basic group OH, OR, NR₂, or SEt) is very weakly activated by the thioether group. Catalysis by magnesium impurities may be involved.With 1-ethylthio-4-dialkylamino-2-butynes (Y NR₂), (E) trisubstituted ethylenic compounds are selectively obtained. The reaction more readily occurs after the addition of cuprous chloride to the Grignard solution, and then its stereoselecitvity may be reversed.     

Untersuchungen über benzylübergangsmetallverbindungen : III. Darstellung und eigenschaften des tetrabenzylthoriums

Tetrabenzylthorium can be obtained in crystalline form by interaction of benzyllithium with thorium tetrachloride. All properties of the compound indicate σ-bonds between the metal atom and the benzyl groups. The IR spectrum of tetrabenzylthorium is discussed together with that of tetrabenzylzirconium.     

A facile synthesis of symmetrical secondary amines from primary amines promoted by the homogeneous catalyst RuCl2(Ph3P)3

Primary amines bearing an α-hydrogen atom are quantitatively converted to symmetrical secondary amines by heating at 185°C for 5 h in the presence of a catalytic amount of RuCl₂(Ph₃)₃.     

Dosage des oléums sulfuriques

The small value of the dissociation constant of the chlorosulfate ion according toSO₃CL^?SO₃+CL^? makes the titration of SO₃ solutions possible in sulfolane, by using chloride ion as titrant. This method can be extended to oleum. The concentrations of the different species are calculated at each time of the titration. This study indicates that the basic properties of the chloride ion do not disturb the sulfonation reaction.     

Reactions d''addition thiophile et carbophile de composes organometalliques sur le groupement thiocarbonyle de deux thiocetones non enethiolisables

2,2,4,4-Tetramethyl-3-pentanethione and adamantanethione react with Grignard reagents (RMgX) to give either thiophilic addition (with R = aliphatic group) or carbophilic addition (with R = unsaturated group). However, two exceptions have been observed.     

Etude magnétothermoélectrique de la transition métal-semiconducteur dans les composés Cr2+ϵSe3 (0 ≤ ϵ ≤ 0,04): II. Etude expérimentale et interprétation: mécanismes de conduction

A negative and very large longitudinal Nernst effect is encountered in the semiconducting compounds of the Cr_2+?Se₃ family. The sign, the amplitude, and the variation of the longitudinal Nernst coefficient Q″(H) versus temperature could be explained either by phonon-drag phenomena or by the presence of magnetic polarons. For an n-type semiconductor, the Seebeck coefficient curve S₀ = f(T) exhibits a peak near the Néel temperature. The vanishing of this peak when a magnetic field is applied confirms the existence of magnetic polarons. Under an infinitely high field, the observed proportionality between the coefficient S(∞) and the temperature shows that the conduction is due to the hopping of polarons (Cutler and Mott criterion). To interpret the thermoelectric power and electrical conductivity a model is proposed in which electrons are localized by the disorder of vacancies (Anderson localization). Each carrier, surrounded by a ferromagnetic cluster and a lattice deformation, is moving by jumps. On another semiconductor compound a reversal of the sign of the longitudinal Nernst effect appears at 47 K, in addition to the change of sign of S₀ at 28 K. Such a behavior may be explained by the presence of two types of carriers at low temperatures.     

Metathese des olefines: intervention d'hydrures de tungstene et nouveau mode de coupure des alkyl-tungstenes

New data indicate that tungsten-hydrogen bonds must be present in catalysts active in olefin metathesis. Evidence for a C-C α-cleavage in alkyl-tungsten derivatives is also adduced, thus allowing a reasonable mechanism to be proposed for olefin metathesis     

Thermogenese: Application des filtrages electronique et numerique inverses en calorimetre a conduction

The results of the application of the numerical and electronic inverse filtering to the same calorimetric output are presented. These two techniques, used to reduce the inertia of conduction calorimeters, give very similar results.     

Metallation des halogenures d'aryle par le tributylstannyllithium dans le tetrahydrofuranne

The metallation of aryl halides with tributylstannyllithium in THF proceeds via at least three different mechanisms whose relative rates depend on the nature of the halogen, the substrate and the experimental conditions. In the case of aryl bromides, a halogenmetal exchange (major process) is competing with a radical mechanism. With aryl chlorides, an arynic process, a halogenmetal exchange and a radical mechanism are involved. Finally, with aryl fluorides, the arynic process is usual, but it may be strongly competed by a radical mechanism whenever suitable experimental conditions are arranged.     

Cristallochimie de TlIII6TeVIO12 et TlI6TeVIO6E6: un exemple original de l'activite´ste´re´ochimique de la pairee´lectronique 6s2(E) du thallium(I)

Both crystal structures of Tl₆TeO₁₂ and Tl₆TeO₆E₆ compounds have been determined, the former by X-ray single crystal techniques, the latter by powder neutron diffraction techniques. They crystallize in the trigonal system, space groupR3¯ the corresponding hexagonal cell parameters area = 9.645(2) Å,c = 9.421(2) Å, anda = 9.5722(3) Å,c = 9.3494(4) Å, respectively, withZ = 3. In both compounds tellurium(VI) is octahedrally coordinated to oxygen atoms with TeO distances of 1.936Åfor the Tl(III)-containing compound, i.e., Tl₆TeO₁₂, and 1.946Åfor Tl₆TeO₆ (Tl(I)). Tl(III) is surrounded by seven oxygen atoms sitting at the summits of a distorted monocapped trigonal prism. Tl(I) is linked to three oxygen atoms, forming a distorted TlO₃ pyramid. The lone pairs brought by Tl(I) are in the positions precedingly occupied by oxygen atoms in the crystal structure of Tl₆TeO₁₂. This is an outstanding example of the crystallochemical role of the lone pairsE which act like oxygen atoms, making Tl^I₆Te^VIO₆E₆ isostructural with Tl^IIITe^VIO₁₂. Structural relationships with fluorite type network are discussed.     

Etudes cristallographique magnétique et par résonance Mössbauer de la variété de haute température du pyrophosphate NaFeP2O7

Single crystals of the high-temperature form of NaFeP₂O₇ have been grown by a flux technique. II-NaFeP₂O₇ crystallizes in the monoclinic $\text{P2}{}_1\text{c}$ space group with lattice parameters: a = 7.298(2) Å, b = 7.874(2) Å, c = 9.536(3) Å, β = 111.85(2)°. The structure refined from 1481 independent reflections leads to R = 0.044 and confirms the work previously published by M. Gabelica-Robert, M. Goreaud, P. Labbe, and B. Raveau (J. Solid State Chem.45, 389, 1982). Magnetic Mössbauer resonance studies have shown the existence of antiferromagnetic ordering with a weak ferromagnetic component below 30 K. The FeO bond is markedly ionic in character due to the highly polarizing power of phosphorus in tetrahedral site.