Danielle Ballivet-Tkatchenko

Insertion reaction of carbon dioxide into Sn–OR bond. Synthesis, structure and DFT calculations of di- and tetranuclear isopropylcarbonato tin(IV) complexes

The reaction of carbon dioxide with the stannane nBu2Sn(OiPr)2 and distannoxane [nBu2(iPrO)Sn]2O leads to the selective insertion into one Sn-OiPr bond generating the corresponding nBu2Sn(OiPr)(OCO2(i)Pr) and nBu2(iPrO)SnOSn(OCO2(i)Pr)nBu2 species. Both compounds are characterised by multinuclear NMR, FT-IR and single-crystal X-ray crystallography. In the solid state, they adopt a dimeric arrangement with bridging isopropoxy and terminal isopropylcarbonato ligands. The X-ray crystal structure of the dinuclear stannane shows that the Sn2O2 ring and the two Sn-OCO2C fragments are nearby coplanar. The same holds for the ladder-type tetranuclear distannoxane. The dimeric structures are also evidenced by solution NMR in non-coordinating solvents. Interestingly, the assignment of the exo and endo tin resonances of the dimeric distannoxane is unambiguous using a labeled 13CO2 experiment. The stability of the dimeric association has been probed in the stannane series on the basis of DFT calculations.

Tin‐Based Mesoporous Silica for the Conversion of CO2 into Dimethyl Carbonate

Sn-based SBA-15 was prepared by reacting di-n-butyldimethoxystannane with SBA-15 pretreated with trimethylchlorosilane (TMCS) to cap the external hydroxyl groups. Small-angle X-ray diffraction (SXRD), infrared spectroscopy (IR), nitrogen adsorption/desorption, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and inductively coupled plasma atomic emission (ICP-AES) measurements allow us to propose that the organotin species are located within the pore channels of the mesoporous host. This novel material catalyzes selectively the coupling of CO(2) with methanol to dimethyl carbonate (DMC). The reaction time-conversion dependence shows that a turnover number (TON) of 16 can be reached at 423 K under 20 MPa, which is among the highest reported so far in the absence of water traps. Moreover, as the catalytic activity is retained after recycling, even higher values can be obtained on a cumulative basis. A further TON increase is observed with the reaction temperature. Interestingly, the tin-based SBA-15 mesoporous material exhibits lower TONs if the TMCS pretreatment is left out. Therefore, the organotin species located outside the channels are far less active than those located within.

Isolation and structural determination of two derivatives of the elusive carbamic acid

The dibenzyl-substituted carbamic acid (PhCH2)2NC(O)OH (1), its deprotonation product [(PhCH2)2NH2]- [(PhCH2)2NCO2] (2) and CoCl(NO)2[PhP(OCH2CH2)2NC(O)OH ]·2MeCOMe(3·2MeCOMe) are reported, the diffractometric study showing the carbamic acids 1 and 3 to be paired through hydrogen bonds.

Synthesis of dimethyl carbonate in supercritical carbon dioxide

The reactivity of carbon dioxide with methanol to form dimethyl carbonate was studied in the presence of the n-butylmethoxytin compounds n-Bu3SnOCH3, n-Bu2Sn(OCH3)2 , and [n-Bu2(CH3O)Sn]2 O. The reaction occurred under solventless conditions at 423 K and was produced by an increase in CO2 pressure. This beneficial effect is primarily attributed to phase behavior. The mass transfer under liquid-vapor biphasic conditions was not limiting when the system reached the supercritical state for a CO2 pressure higher than 16 MPa. Under these conditions, CO2 acted as a reactant and a solvent.

Metallation reactions of diphosphiranes: New access to σ- and π-diphosphaallyl complexes

Abstract The metallation reactions of the functionalized diphosphiranes 1a,b with the anionic metal transition complexes Na[(Cp)nM(CO)m] (M  Mo, W, or Co) afford σ- or π -diphosphaallyl complexes depending on the substituents of the intracyclic carbon atom. The same complexes are also obtained from their photochemical isomers, the 1,3-diphosphapropenes 2a,b. The complexes are thermally labile as shown by variable-temperature NMR spectroscopy. Upon heating, the σ-diphosphaallyl cobalt complex 3aC is irreversibly transformed into the π-complex 4aC. In contrast, with M  Fe and in toluene solution at reflux, reduced 1,3-diphosphapropenes 5a,b are obtained. Further, the gem-dihalogenated diphosphiranes 1c,d and their isomers 2c,d lead quantitatively to 1,3-diphosphaallene 6 under the same metallation conditions. The mechanism of the coordination reactions is discussed.

Diphosphiranes: New Precursors of σ - or π - Diphosphaallyl Complexes

Abstract The metalation reactions of the functionalized diphosphiranes 1a–b with the anionic metal transition complexes (M = Mo, W, Co) afford the σ- or π- diphosphaallyl complexes (2 or 3, respectively) as function of the intracyclic carbon atom substituents. The thermal lability of these complexes is detected by variable-temperature NMR spectroscopy.

A novel two-dimensional organostannoxane coordination network promoted by phenazine: Synthesis, characterization and X-ray structure of 2∞{[n-Bu2(μ-OH)SnOSn(μ-η2-O3SCF3)n-Bu2]2[n-Bu2(η1-O3SCF3)SnOSn(μ-OH)n-Bu2]2}

Reaction of the dimeric hydroxo di-n-butylstannane trifluoromethanesulfonato complex [n-Bu2Sn(μ-OH)(H2O)0.5(η1-O3SCF3)]2 (1) with phenazine (C12H8N2, Phz) (2) in dichloromethane at room temperature in a 1:3 molar ratio yielded the novel two-dimensional organometallic coordination polymer 2∞{[n-Bu2(μ-OH)SnOSn(μ-η2-O3SCF3)n-Bu2]2[n-Bu2(μ-OH)SnOSn(η1-O3SCF3)n-Bu2]2}2∞{[n-Bu2(μ-OH)SnOSn(μ-η2-O3SCF3)n-Bu2]2[n-Bu2(μ-OH)SnOSn(η1-O3SCF3)n-Bu2]2} (3), together with the phenazinium trifluoromethanesulfonate salt [C12H9N2]+ [CF3SO3]−, crystallographically isolated in two different structural arrangements, free 4 and in π–π aromatic stacking interaction with independent intercalated non-protonated phenazine molecules 5. Organometallic coordination polymer 3 consists of an infinite one-dimensional chain composed of tetrameric hydroxo tetra-n-butyldistannoxane units bridged by bidendate trifluoromethanesulfonate ligands, (μ-η2-O3SCF3). The formation of weak intermolecular interactions between nearest-neighbour chains through the pseudo-terminal trifluoromethanesulfonate ligands (η1-O3SCF3) gives rise to the expansion of an unexpected supramolecular two-dimensional network. The re-crystallisation of 3 in methanol leads to the polymorphic structure 2∞{[n-Bu2(μ-OH)SnOSn(μ-η2-OSO2CF3)n-Bu2]}2∞{[n-Bu2(μ-OH)SnOSn(μ-η2-OSO2CF3)n-Bu2]} (3b).

Linear Organic Carbonates

The most common and successful method for producing organic carbonates, including polycarbonates, has been based for long time on the reaction between an alcohol or phenol and phosgene. The existing strict environmental regulations and the expanding market for organic carbonates do not assure that this technology can continue to have a leading role in this area, due to the inherent riskfulness of the processes. The market expansion of dimethyl carbonate (DMC), diphenyl carbonate (DPC), and bisphenol A polycarbonate (BPA-PC) is a reality, finding its driving force from the industrialization of alternative routes by EniChem (Italy) and UBE (Japan). This favorable situation can be foreseen for other carbonates.

Changes in properties of V2O5–K2SO4–SiO2 catalysts in air, hydrogen and toluene vapors

V2O5–K2SO4–SiO2 catalysts were studied by TG, DTA, TPR and XRD methods. During activation NH4VO3 and (COOH)2, used for impregnation of the support, decompose in air below a temperature of 350°C. Over 350°C oxidation of vanadium up to V5+ and changes in the catalyst reducibility occur. In TPR using pure hydrogen, the freshly activated catalyst is reduced in three steps. The first peak with a maximum around 430°C is a result of reduction of the vanadium oxide species. The second and the third TPR peaks correspond mainly to the reduction of sulfate species to H2S. It was found that vanadium oxides noticeably enhanced the reduction of sulfate to H2S. Similar TPR profiles were found after catalytic tests (vapor phase oxidation of toluene by air) and after reduction of the same catalyst by H2, and its reoxidation by air in some particular conditions. By increasing temperature and prolonging time of activation, or by prolonging time-on-stream of toluene oxidation the reducibility of vanadium oxides decreases and the easily reducible part of sulfate species is converted into a less reducible part.

CO2 as a C1-Building Block for Dialkyl Carbonate Synthesis

Carbon dioxide, one of the major man-made greenhouse gas, is a renewable resource of carbon which can be viewed as a C1 synthon to build valuable chemicals. The development of new applications is of major interest considering CO2 conversion and environmentally friendly reactions. As chemical catalysis offers interesting options, we are studying the molecular design of catalysts for the formation of dialkyl carbonates from alcohols and CO2. This paper reports results on the mechanistic approach for dialkyl carbonate formation with alkoxybutyl tin(IV) compounds. The insertion of CO2 into Sn-OR bonds (R = Me, 1Pr) occurs at atmospheric pressure and room temperature leading to alkylcarbonato tin fragments, Sn-OCO2R. For dialkoxy derivatives, only one Sn-OR bond reacts with CO2 due to a dimerization pathway. Preliminary DFT calculations confirm that the dimer is more stable than the corresponding monocarbonated and dicarbonated monomers. Under catalytic conditions, n-Bu2Sn(OMe)2 gives dimethyl carbonate (selectivity = 100%). Pressure and temperature effects as well as reaction time were studied. The best yield in dimethyl carbonate is obtained under supercritical CO2 conditions (200 bar, 145 °C). The carbonated distannoxane, (n-Bu2SnOMe)(n-Bu2Sn(OCO2Me)O, has ben identified as an intermediate. The relevance of this species for dimethyl carbonate synthesis is discussed.