Les villes tunisiennes : un essai de prospective à l'an 2009

Some Prospects for Tunisian Cities in 2009. Interregional disparities in Tunisia have worsened because of the present demographic growth. The future of the Tunisian urban system, regional sub-systems, is already influenced by the growth or the regression potentialities specific to each urban unit. In order to elaborate urban demographic perspectives, it is necessary to take into account the regional aspects in the dynamics of population. After analysing methodological problems and evolution factors, a panorama of the urban space in the year 2009 is presented. The reinforcement of the Tunis and coastal regions would not strongly affect the spatial distribution of the Tunisian population. In the inner part of the country, a stronger natural movement could counterbalance, it would seem, the negative effects of the emigration to more attractive regions. But, as regards structure by age, the contrasts would be reinforced.Le déséquilibre régional tunisien a été exacerbé par la croissance démographique contemporaine. Le devenir du système urbain tunisien, des sous-systèmes régionaux, est déjà engagé par les potentialités de croissance ou de régression propres aux villes. L'élaboration des perspectives démographiques des villes passe par la prise en compte de la dimension régionale des évolutions. Après l'analyse des contraintes méthodologiques et des facteurs d'évolution, l'auteur dresse un panorama de l'espace urbain en l'an 2009. Le renforcement de la région tunisoise et des régions littorales ne bouleverserait pas la distribution spatiale de la population tunisienne. Il semblerait que la dynamique démographique plus forte de l'intérieur du pays compense les effets négatifs de la composante migratoire qui lui est fortement dévavorable. Les oppositions se renforceraient davantage par contre au niveau des structures par âge.Picquet Michel. Les villes tunisiennes : un essai de prospective à l'an 2009. In: Espace, populations, sociétés, 1988-2. L'urbanisation en Afrique - Urbanization in Africa. pp. 199-212

Firsts lysidinyl- and lysidinium-triphosphines Pd(II) complexes

International audienceThe preparation of first lysidinyl-triphosphine ligand (named Triphosline) is described in three steps which are first a Michael type addition of imidazolidine (or lysidine) to diethylvinylphosphonate, second a phosphonate reduction with LiAlH4 and third an anti-Markovnikov radical addition of the primary phosphine to diphenylvinylphosphine. The Triphosline behaves as a tridentate P-coordinating ligand in palladium(II) complexes. The dangling lysidine function is then cleanly and totally alkylated by methyl iodide to lead to a new kind of lysidinium-triphosphine complexes. Subsequent anion exchange with TlPF6 affords the first example of a chloride free lysidinium-triphosphine palladium complex which has been fully characterized by spectroscopic and analytical methods

Di-n-butyltin(IV)-catalyzed dimethyl carbonate synthesis from carbon dioxide and methanol: An in situ high pressure 119Sn{1H} NMR spectroscopic study

The reactivity of five di-n-butyltin(IV) complexes, n-Bu2Sn(OR)(2) (1), n-Bu2SnO (3), [n-Bu2Sn(OR)](2)O (4), (n-Bu2SnO)(2)(CO2) (6) and (n-Bu2SnO)(6)[(n-Bu2SnOR)(2)(CO3)](2) (7) (R = CH3), with CO2, suggested as possible catalyst precursors and key-intermediates for the direct synthesis of dimethyl carbonate from carbon dioxide and methanol, has been investigated using high-pressure Sn-119{H-1} NMR (HP-NMR) spectroscopy. Four of the five precursors studied, i.e. 3, 4, 6 and 7 give rise to an identical Sn-119{H-1} NMR pattern which can be explicitly attributed to the fingerprint of the dimeric form of the 1-methoxy-3-methylcarbonatotetrabutyldistannoxane {5}(2). However, with 1, a new pair of signals is observed in addition to the characteristic Sn-119{H-1} NMR resonances of the dimeric hemicarbonato species {2}(2) and {5}(2), which can be attributed to the in situ formation of an unprecedented species suggested to be the trinuclear carbonato di-n-butyltin(IV) complex, 8. (C) 2011 Elsevier B. V. All rights reserved

Ligands hybrides (synthèse et chimie de coordination)

Ce manuscrit traite de la synthèse de ligands hybrides et de leur chimie de coordination. La première partie est consacrée aux ligands Cp-imidazole, Cp-imidazolium et Cp-phosphine. Plusieurs voies de synthèse ont été développées pour accéder à ces ligands mixtes. Leur chimie de coordination est également étudiée avec le titane. Dans la seconde, une technique développée au laboratoire pour synthétiser des phosphine-oléfines a été appliquée pour obtenir un ligand phosphine-diène, possédant trois sites de coordination potentiels. Avec différents métaux de transitions, nous avons étudié les modes de coordination de ce ligand hybride. Certains complexes formés ont également été testés en catalyse. Dans la troisième partie a été étudiée la chimie de coordination de bisaminophosphoniums vis-à-vis du titane. Ces ligands ont pu être coordinés à différents états de déprotonation, conduisant à des complexes cationiques ou neutres.This manuscript deals with the synthesis of hybrids ligands and their coordination ability. The first part is dedicated to Cp-imidazole, Cp-imidazolium and Cp-phosphine ligands. Several synthetic routes have been developed to reach these mixed ligands and their coordination chemistry has been studied with titanium. In a second part, a method developed in our laboratory to synthesize phosphine-olefines was applied to obtain a phosphino-diene bearing three potential coordination sites. We have studied the coordination modes of this hybrid ligand using various transition metals and some of the formed complexes were tested in catalysis. In the third part is described the coordination chemistry of bisaminophosphoniums towards titanium. These ligands were coordinated in various deprotonation states, leading to cationics and neutrals complexes.DIJON-BU Doc.électronique (212319901) / SudocSudocFranceF

Diffusional transport in ionic liquids: Stokes-Einstein relation or "sliding sphere" model ? Ferrocene (Fc) in imidazolium liquids

International audienc

Synthesis of new cationic donor-stabilized phosphenium adducts and their unexpected P-substituent exchange reactions

International audienc

High-pressure NMR spectroscopy: An in situ tool to study tin-catalyzed synthesis of organic carbonates from carbon dioxide and alcohols. Part 2 [1]

Dialkoxide diorganotin(IV) complexes are known to readily react with carbon dioxide under pressure and they are considered as suitable catalyst precursor models for the direct synthesis of organic carbonates. To gain a better understanding of CO2 insertion processes with Sn-OR bonds, the reactivity of n-Bu2Sn(OCH(CH3)(2))(2) (2) was investigated using high-pressure NMR (HP-NMR) spectroscopy. In deuterated solvents (isopropanol-d(8) and toluene-d(8)) under 50 bar of CO2 pressure at 80 degrees C, Sn-119{H-1} NMR experiments revealed the exclusive formation of an unprecedented tetraorganodistannoxane species, characterized as the bis[diisopropycarbonatotetrabutyldistannoxane] complex, {[n-Bu2Sn(OC(O)OCH(CH3)(2))(2)](2)O}(2) {7}(2). The formation of hemicarbonato ligands resulting from CO2 insertion was also confirmed by FT-IR and C-13 NMR spectroscopies. To the best of our knowledge, spectroscopic detection of the distannoxane species 7 is unprecedented. (C) 2015 Elsevier B.V. All rights reserved