Synthesis and molecular structure of [Al(CH3)2]2[C10H22N4] [Al(CH3)3]2: Condensation product of trimethylaluminum and a multidentate open-chain amine

The crystalline condensation product [Al(CH₃)₂]₂[C₁₀H₂₂N₄][Al(CH₃)₃]₂ is prepared from reaction of the multidentate open-chain amine 1,4-bis(3-aminopropyl)piperazine with trimethylaluminum in methylene chloride. The compound crystallized in the monoclinic space groupC2/c with unit cell parametersa=25.166(12),b=7.268(4),c=17.316(4) Å,=115.3(4)°, andD _c =1.06 g cm^–3 forZ=4. Least-squares refinement based on 1054 observed reflections with intensitiesI 3(I) in the range 2<2<45° led to a finalR factor of 0.053 (R _w =0.064). The title compound resides on a crystallographic center of symmetry with independent Al-N distances of 1.889(5), 2.058(5), and 2.030(5) Å.     

Reduction electrochimique du ferrocene

A well characterized 1e^? reversible polarographic wave is observed at low temperature (? ?30°C) for ferrocene and methylferrocene in dimethylformamide. At higher temperatures, a 2e reductive cleavage of the molecule occurs.     

Cyclisations par l'intermédiaire de fonctions phénylthioet phénoxy-carbamyle. I. Diphényl-1,2-alcoyl-5-dioxo-3,6-hexahydro-triazines-1,2,4

The N-(p-nitrophenoxy-carbonyl) and N-(phenylthio-carbonyl) derivatives of α-amino-acyl-hydrazides cyclize in presence of diazomethane, yielding hexahydro-1, 2, 4-triazines with simultaneous formation of p-nitro-anisole or thio-anisole respectively. The molecules with a phenoxycarbonyl function such as N-(phenoxycarbonyl)-glycyl-(N, N′-diphenylhydrazide) give the corresponding ring products and anisole only in solvents with high dielectric constant (e.g. nitromethane). The phenylthio-carbonyl derivatives give the same ring products in presence of lead acetate by the intervention of HO^?. The p-nitrophenoxycarbonyl derivatives give rise to the same cyclisations in the presence of pyridine by the intermediate of carbamyle-pyridinium ion acting as electrophile. These different types of intramolecular reactions are illustrated by the formation of 1, 2-diphenyl-5-alcoyl-3, 6-dioxo-1, 2, 4-hexahydro-triazines.     

Colour formation in poly(ethylene terephthalate) during melt processing

The discolouration, that occurs in virgin poly(ethylene terephthalate) - PET during melt processing, was studied using various bulk and surface analytical techniques. Proton nuclear magnetic resonance (¹H NMR) was used to study the bulk chemical changes occurring in the polymer during thermo-oxidative degradation. Chemical derivatisation with trifluoroacetic anhydride (TFAA) was used to label the hydroxyl groups introduced on the polymer surface by thermal oxidation.From the surface analysis studies using photoacoustic Fourier transform infrared spectroscopy (PA/FT-IR), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) and X-ray photoelectron spectroscopy (XPS) it was evident that colour formation starts initially with the hydroxylation of the terephthalic ring. Further, the formation of additional carbonyl functionalities and conjugated chromophoric systems complete the colour formation process.     

π Coordination de diazoalcanes sur le dicyclopentadienylvanadium (II)

The X-ray crystal and molecular structure of η⁵-cyclopentadienyl-η¹-2,4-diphenylcyclobut-1-en-3-oneiron dicarbonyl (I) was determined (monoclinic crystals, a 9.2371(9), b 26.4502(9), c 8.2450(7) Å, β 115.502(6)°, Z = 4, space group P2₁ /c, 1902 unique reflections, R = 0.068). Molecule I contains the η¹-cyclobut-1-en-3-one ligand with three sp² and one sp³ carbon atoms in a four-membered cycle, σ-bonded to the CpFe(CO)₂ fragment (bond distance FeC 1.935(6) Å).     

Stereochemistry at titanium in the sulfur dioxide insertion reaction of titanocene compounds

The insertion reaction of SO₂ has been studied for the two diastereoisomeric forms of η⁵-C₅H₅-η⁵-C₅H₄ CHMePhTi(C₆F₅)CH₃. The reaction is regioselective and stereospecific. Arguments that it involves a retention at the titanium atom are given.     

Insertion de so2 dans la liaison titane—carbone: I. Diastereotopie et diastereoisomerie engendrees par la presence d'un atome de soufre chiral dans les produits d'insertion

Sulfur dioxide insertion reactions in titanium—carbon bonds are studied with two types of titanocene complexes: Cp₂Ti(C₆F₅)R and CpCp′Ti(C₆F₅)R. The NMR spectra of the insertion products from the first type of complex are typical for O-sulfinated complexes having a chiral sulfur atom. Starting from the second type or complex two diastereoisomers have been detected (diastereoisomery Ti, S).     

The use of metallocenic esters of n-hydroxysuccinimide for metallohapten synthesis

Different organometallic markers have been described in a new technique for the labelling of many drugs. Thus metallocenic esters of [M = (;CO)₃CrC₆H₅?; (;CO)₃CrC₆H₅?(;CH₂)₃?; η-C₅H₅?FeC₅H₄?; (;CO)₃MnηC₅H₄?; (;CO)₃Mn?ηC₅H₄COCH₂CH₂?; ηC₅H₄(;ηC₅H₅)Co⁺PF^?₆] react with primary or secondary amine drugs [DRUG?NHR] for a psychostimulant drug: amphetamine; tricyclic antidepressants—desipramine and nortriptyline; a vasodilator—histamine; an adrenergic substance—norfenefrine; and for a central stimulant—meth-amphetamine, to give the metallohaptens MCON(;R)—DRUG. All these compounds have been fully characterized by different analytical methods and have potentialities for biological assays. This synthetic route was found better than one presented previously which utilized the metallocenic acid chloride MCOCI as intermediate, and could be proposed as a general synthetic route for labelling biological compounds which possess an amino group.     

Surface influence on the rotational and translational dynamics of molecules confined inside a mesoporous carbon xerogel

Low-field nuclear magnetic resonance techniques are employed to extract information about the effects introduced by the interaction with the surface on the rotational and translational dynamics of molecules confined inside a mesoporous carbon xerogel. The molecules under study were water, cyclohexane, and hexane. They were chosen due to their different interaction strength with the carbonaceous matrix. Frequency dependent longitudinal relaxation measurements, using the fast field cycling technique, allowed extraction of the fractal dimension of the carbon xerogel surface. It was observed that the measured value is influenced by the molecule affinity to the surface. Diffusion measurements, using the pulse field gradient technique, have revealed that the stronger interaction with the surface of cyclohexane and hexane molecules leads to an increased diffusive tortuosity, as compared with water.