Extraction-polarographic determination of cobalt(II) and nickel(II) as 2,2′-bipyridine complexes in acetonitrile

The tris(2,2′-bipyridine)cobalt(II) complex gives a reversible d.c. wave with E$\text{1}\text{2}$ = ?1.02 V vs. SCE and a sharp differential pulse peak at E_p = ?1.03 V in a salted-out acetonitrile phase. A simple selective method is described for the determination of cobalt(II); down to 0.25 μg of cobalt(II) can be determined in presence of large amounts of Ni, Zn, Cd, Pb, and Cu; iron(III) can be masked with sodium fluoride. The method is applicable to the determination of >0.0l% cobalt in nickel salts and >5 × 10^?5% cobalt in iron salts. Nickel(II) can also be extracted from aqueous solution and determined by differential pulse polarography, even in presence of a 20-fold amount of cobalt(II) by masking with EDTA; >0.01% of nickel in cobalt salts can be determined reproducibly.     

Structure du stearyl-velutinal,sequiterpenoide naturel de lactarius velutinus bert1.

Stearyl-velutinal, a new natural sesquiterpenoi̋d isolated from lactarius velutinus Bert., has the structure $\text{1}$; this very labile compound is responsible for the dark-blue reation of the fungus to the ‘sulfo-vanilic’ mixtures.     

Role du methyle 4β dans la formation des oxetanones en serie steroïde. Cas du cycle B.

The formation of oxetanones $\text{5}$ from bromoketonee $\text{2}$ requires the presence of a β-methyl group at C-4. The yield of the reaction $\text{2}$→$\text{5}$ is improved by addition of water to the medium.     

Oxydes de type perovskite du systeme CaNbO

Three perovskite-like phases of the CaNbO system have been isolated, $\text{Ca}{}_{\mathrm{x}}\text{NbO}{}_3\text{(0.9 ? x ? 1),}\text{Ca(Ca}{}_{\mathrm{x}}\text{Nb}{}_{\mathrm{1?x}}\text{)}\text{O}{}_3\text{(0 ? x ?}\text{1}\text{3}\text{)}$, and Ca₃Nb₂O_8?x. X-ray powder diffraction and electron microscopy and diffraction were used to obtain crystallographic data of these phases. The high temperature form of Ca(Ca_xNb_1?x)O₃ perovskites, where calcium ions occupy partially the octahedral sites, presents an orthorhombic symmetry and quasi-periodic twin bands like Ca_xNbO₃ compounds. Two monoclinic forms (for $\text{x =}\text{1}\text{3}$ and $\text{x =}\text{1}\text{4}$) were found by heating Ca(Ca_xNb_1?x)O₃ compounds at lower temperature for long periods; ordering of calcium and niobium ions in octahedral sites is proposed for that structure. The Ca₃Nb₂O_8?x compound presents a quadratic cell: ordering of the cations derived from (NH₄)₃FeF₆ structure is proposed in agreement with the observed space group $\text{P4}\text{nnc}$. A new multiple-phase family, with general formula Ca_nNb_nO_3n+2, was obtained for n = 4.25, 4.5, and 5; electron microscopy shows intergrowth phenomena.     

Etude cinetique de la copolymerisation alternee de l'indene et du methacrylate de methyle en presence de sesquichlorure d'ethylaluminium

The copolymerization of indene with methyl methacrylate (MAM) initiated by u.v. irradiation, in the presence of ethylaluminium sesquichloride (SCEA) as a complexing agent, yields alternating copolymers when [Indene] ≥ [MAM] ≥ [SCEA]. Values of $\text{M}$_n of the copolymers range from 32,000 to 900,000, depending on the concentrations of the reagents, reaction temperature and intensity of u.v. light. The kinetics can be explained simply by assuming a statistical copolymerization of indene with a MAM-SCEA binary complex, but intervention of a ternary complex SCEA-MAM-indene cannot be discarded. At high MAM concentrations, the free MAM becomes involved in the copolymerization.     

Rearrangement spinal en serie a/b cis : conversion du lithocholate de methyle en derives du d-homoandrostane

A new backbone rearrangement is observed in A/B $\text{cis}$ methyl lithocholate derivatives. It is initiated from the C-3 carbon either by dehalogenation of the chloroesters $\text{1}$ by AgSbFg₆ or by the action of the triflic anhydride on the si1y1ated ether $\text{2}$. This rearrangement leads to methyl diacholenate $\text{3}$ and new lactones in D-homoandrostane series $\text{5}$ and $\text{6}$. The differences of behaviour between A/B $\text{cis}$ and A/B $\text{trans}$ series and the mechanism of rearrangements are discussed.     

Etude structurale de derives du fer carbonyle: II. Structure cristalline et moleculaire d'un complexe du fer carbonyle avec la 2-mercapto-pyridine,C5H4N(CO)6Fe2-μ4-S-Fe2(CO)6SC5H4N

The crystal and molecular structure of a complex prepared by reaction between Fe₃(CO)₁₂ and 2-mercaptopyridine and of formula C₅H₄N(CO)₆Fe₂-μ₄-S-Fe₂(CO)₆SC₅H₄N has been determined by a single-crystal X-ray study. The compound crystallises in the monoclinic space group $\text{P}\text{2}{}_1\text{n}$, with Z = 4. Data were collected on a NONIUS CAD-4 automatic diffractometer. The structure was solved both by the heavy-atom method and direct methods and refined to R and R″ values of 0.041 and 0.038 for 2089 independent reflections. The molecule contains four Fe(CO)₃ groups with two ironiron bonds bridged in a different way, and a sulphur atom tetrahedrally coordinated to the four iron atoms.     

Solution of hydrogen in palladium/copper alloys

The solution of hydrogen in $\text{Pd}\text{Cu}$ fcc substitutional alloys has been examined in the region of low hydrogen contents. Relative partial molar enthalpies of absorption at infinite dilution are found to be somewhat less exothermic for the alloys than for palladium but the change with X_Cu is small. Partial excess entropies of absorption decrease with X_Cu but not as markedly as for the other Pd/group IB alloys. Relative electrical resistance relationships for $\text{Pd}\text{Cu}$ alloys have been determined as a function of their hydrogen contents. Interstitial hydrogen increases the relative electrical resistance to a lesser extent with increase of X_Cu, but the absolute increase of resistance is nearly invariant with X_Cu.     

Phosphazene spirannique a partir de derives du phophore dicoordine

The reaction of azidoalcohol $\text{2}$ on triazaphosphole $\text{1}$ takes place according to pathway $\text{a}$ and not $\text{b}$, as shown by the isolation of spirannic phosphazene $\text{3}$. The diazadiphosphetidines $\text{4}$, dimers of $\text{3}$ are also caracterized.     

Contributions to the complexometric determination of cation mixtures: Simultaneous titration of iron(iii) and aluminium in the presence of ammonium thiocyanate as indicator

With thiocyanate as indicator iron(III) and aluminium(III) can be titrated simultaneously if [Fe⁺³]/[Al⁺³] ? $\text{1}\text{4}$; iron(III) is titrated directly with EDTA, and aluminium(III) is determined by back-titration of the excess of EDTA with cobalt nitrate solution in an acetone-water medium.     

Conversion directe des phospholes en dihydro-6,7 phosphepines dans la sphere de coordination du tungstene

In the presence of AlCl₃, [1-β-chloroethyl-3,4-dimethylphosphole]pentacarbonyltungsten($\text{1}$) rearranges into [1-chloro-3,4-dimethyl-6,7-dihydrophosphepin]pentacarbonyltungsten ($\text{3}$).     

Contribution à l'étude structurale de la wüstite solide de haute température

The structure of wüstite Fe_1?zO is studied by neutron diffraction on one polycrystalline sample under equilibrium conditions at high temperature. The mean isotrope temperature factor B is expressed as a sum of two parts, B_Th and B_St, which vary linearly with a single parameter, respectively temperature and z. A classification is established for clusters ($\text{m}\text{n}$) settled from m vacancies in octahedral sites and n Fe^III ions in interstitial sites. Sixteen values have been experimentally determined for the vacancies to interstitials ratio $\text{? =}\text{(z + t)}\text{t}\text{=}\text{m}\text{n}$. A constant value of ?, which is lower than 3, is observed. This result characterizes the short-range order. It eliminates several possibilities of clusters like those obeying the relation $\text{? =}\text{(1 + 3n)}\text{n}$. Other clusters, namely ($\text{16}\text{6}$) or ($\text{40}\text{14}$), might agree. The ($\text{8}\text{3}$) and ($\text{9}\text{4}$) clusters obtained from ($\text{4}\text{1}$) clusters joined by an edge would be the more likely. An analysis of diffuse scattering eliminates the hypothesis of large domains with inverse spinel structure. The structural differences between the three varieties W₁, W₂ and W₃ would not be found in a structural change of clusters.     

Phosphures ternaires de lithium. II. Structure cristalline de LiBeP

This structure is determined with X rays and neutron diffraction. The cell is tetragonal with a = 3.617 and c = 6.032, Å, group $\text{P4}\text{n}\text{mm, z = 2}$. The refinement gives R = 0.06. The bonds are discussed and the structure, anti-PbFCl type, is replaced in the Flahaut's classification of MXY compounds.     

Metallextraktion mit N-thiobenzoyl-N-phenylhydroxylamin: Extraction of metal ions with N-thiobenzoyl-N-phenylhydroxylamine

The extraction parameters pH_{$\text{1}\text{2}$} and K_ex for Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb with N-thiobenzoyl-N-phenylhydroxylamine are reported. N-Thiobenzoyl-N-phenylhydroxylamine extracts metals from more strongly acidic solutions than does N-benzoyl-N-phenylhydroxylamine. Iron(III) is extracted as a 1:2 chelate with the extracant, whereas iron(II) forms the expected tris chelate by oxidation. The other bivalent ions are extracted as their bis chelates.     

Etude structurale d'un nouveau tellurate alcalin: Na2TeO4. Evolution de la coordination du tellure(VI) et du cation quand on passe du cation lithium au sodium

Single crystal Na₂TeO₄ has been prepared by hydrothermal synthesis and its structure determined from three dimensional X-ray analysis. The crystal is monoclinic, space group $\text{P}\text{P2}{}_1\text{c}$ with a = 10.632(5)Å, b = 5.161(2)Å; c = 13.837(11)Å, and β = 103.27(4)°. The crystal structure is built up of chains of Te(VI)O₆ octahedra parallel to the [010] axis which can be formulated as [TeO₄]_n^2n?. All sodium cations are in very distorted octahedral coordination.     

Obtention de 3 types de derives du bore: esters aminoboriques tris n-boranes,esters amio boriques bis n-boranes et aminalcools n-boranes a partir de la reaction d'aminalcools-1,2 avec BH3.THF et BH3DMS. mise en evidence d'une coordination interner B←N

The reactions of 1,2-aminoalcohols with BH₃.THF or DMS lead to various title compounds, depending on the reaction conditions. The structures have been determined using ¹¹B, ¹H nmr and i.r. spectroscopy and selected reactions. The conclusions differ from previous r$\text{e}$sults: we were in particular able to evidence intramolecular N←B coordination in structures of type $\text{d}$ and $\text{e}$.     

Etude cristallochimique des phases de type perovskite du systeme Th0.25 NbO3NaNbO3

The compound Th_0.25 NbO₃ melts congruently at 1390°C. Single crystals obtained by slow cooling from the melt are transparent and show uniaxial optical properties. A single-crystal X-ray analysis confirms the tetragonal cell found by Kovba and Trunov from a powder data and gives a = 3.90 Å and c = 7.85 Å. No systematic absence of the hkl reflections is observed on precession films. The relative intensities of the main reflections are characteristic of a perovskite-like arrangement ABO₃ whose large dodecahedral A sites are only partly occupied. Several domains have been found in the perovskite-type solid solution (1 ? x) Th_0.25NbO₃-x NaNbO₃. For 0 ? x ? 0.5 the phases have a tetragonal cell with $\text{a ? a}{}_0$ and $\text{c ? 2a}{}_0$ as in pure Th_0.25 NbO₃. When 0.6 ? x ? 0.8 the corresponding phases crystallize with a small cubic cell ($\text{a}{}_0\text{? 3.9}$Å), while phases with 0.9 ? x ? 1 have an orthorhombic cell ($\text{a ? 2}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{a}{}_0\text{, b ? 2}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{a}{}_0\text{, c ? a}{}_0$).     

Chimie des sucres sans groupements protecteurs : synthese de carbamates,d'urees et de thiourees en position 1 du lactose

The anomeric hydroxyl of lactose was carbamoylated selectively by treating the free sugar with alkylisocyanates, thus without preliminary protection of the other hydroxyls of the lactose molecule. Moreover, the readily available 1-aminolactose and 1-octyl-aminolactose reacted with isocyanates and isothiocyanates to afford selectively $\text{N}$-lactosyl $\text{N′}$-alkylureas and $\text{N}$-lactosyl $\text{N′}$-alkylthioureas, respectively.     

Etude expérimentale et théorique de la photolyse de dérivés du cycle pyrazolone

When irradiated in protic solvents such as water and primary alcohols, pyrazolinone derivatives undergo photocleavage between the two nitrogen atoms. Substituting the C-4 atom with an electronegative group stabilizes the open chain which is obtained but a thermal transposition takes place from the linear intermediate when C-4 carries a hydrogen atom or a methyl group. The $\text{STO}\text{3G}$abinitio scheme was used to study the photocleavage and the influence of the C-4 substituent, giving evidence of a mechanism which involves triplet excited states of the π, σ^* type.     

Etude cristallochimique de derives du chrome(0) : I. Structure cristalline et moleculaire du benzoate de methyle chrome dicarbonyle thiocarbonyle

The crystal and molecular structure of methylbenzoatechromium dicarbonyl thiocarbonyl has been determined by a single-crystal X-ray study. The compound crystallizes with two molecules in a unit cell of symmetry P$\text{1}$, with the following parameters: triclinic system, a = 7.108(3), b = 10.340(4), c = 8.523(3) Å; α = 89.75(6), β = 95.89(4), γ = 105.50(4)°; V = 601 ų; d_m = 1.57 ± 0.05, d_c = 1.56. The structure has been refined to R and R″ values of 0.030 and 0.038 respectively, for 1963 independent reflections. The main feature of the molecule is the C_s symmetry of the Cr(CO)₂CS group with a CrC(S) bond length of 1.792(2) Å, shorter than the CrC(O) bond length, mean: 1.849(3) Å.